Book U. S. DEPARTMENT OF AGRICULTURE, BUREAU OF ENTOMOLOGY— BULLETIN No. 100. L. O. HOWARD, Entomologist and Chief of Bureau. THE INSECT ENEMIES OF THE COTTON BOLL WEEVIL. W. DWIGHT PIERCE, Agent and Expert, ASSISTED BY R. A. CUSmiAN AND C. E. HOOD, Agents and Experts, UNDER THE DIRECTION OF W. D. HUNTER, Agent and Expert, In Charge of Southern Field Crop Insect Investigations. Issued April .S, 1912. y WASHINGTON: GOVERNMENT PRINTING OFFICE. 1912. / U. S. DEPARTMENT OF AGRICULTURE, BUREAU OF ENTOMOLOGY— BULLETIN No. 100. L. O. HOWARD. Entomologist and Chief of Bureau. THE INSECT ENEMIES OF THE COTTON BOLL WEEVIL. • W. DWIGHT PIERCE, Agent and Expert, ASSISTED BY R. A. CUSHIIAN AND C. E. HOOD, Agents and Experts, UNDER THE DIRECTION OF W. D. HUNTER, Agent and Expert, In Charge of Southern Field Crop Insect Investigations. Issued April 3, 1912. WASHINGTON: GOVERNMENT PRINTING OFFIOE, 1912. 9 (^ '-^'tc^ ,CST7 B UREA U OF ENTOMOLOGY. L. O. Howard, Entomologist and Chief of Bureau . C. L. Marlatt, Entomologist and Acting Chief in Absence of Chief. R. S. Clifton, Executive Assistant. W. F. Tastet, Chief Clerk. F. H. Chittenden, in charge of truck crop and stored product insect investigations. A. D. Hopkins, in charge of forest insect investigations. W. D. Hunter, in charge of southern field crop insect investigations. F. M. Webster, in charge of cereal and forage insect investigations. A. L. Quaintance, in charge of deciduous fruit insect investigations. E. F. Phillips, in charge of bee culture. D. M. Rogers, wl charge of preventing spread of moths , field tvork. RoLLA P. Currie, in charge of editorial work. Mabel Colcord, in charge of library. Southern Field Crop Insect Investigations. W. D. Hunter, in charge. W. D. Pierce, J. D. Mitchell, G. D. Smith, E. A. McGregor, Harry Pinkus, W. A. Thomas, D. C. Parman, B. R. Coad, engaged in cotton boll weevil inves- tigations. F. C. BisHOPP, A. H. Jennings, H. P. Wood, W. V. King, G. N. Wolcott, engaged in tick life-history investigations. A. C. Morgan, G. A. Runner, S. E. Crumb, engaged in tobacco insect investigations. J. L. Webb, T. E. Holloway, E. R. Barber, engaged in sugar cane and rice insect investigations. R. A. CooLEY, D. L. Van Dine, Wilmon Newell, A. F. Conradi, C. C. Krumbhaar, collaborators. 2 f^. m % ^^^ ^5 191? LETTER OF TRANSMITTAL. U. S. Department of Agriculture, Bureau of Entomology, Washington, D. C, September 28, 1911. Sir: I have the honor to transmit herewith a manuscript entitled "The Insect Enemies of the Cotton Boll Weevil," by Messrs. W. Dwight Pierce, R. A. Cushman, and C. E. Hood, agents and experts engaged in cotton boll weevil investigations. The present manu- script contains a complete summary of the studies of the boll-weevil parasites conducted since 1905. The boll weevil is now known to be attacked by 29 species of parasites and 26 species of predatory insects, most of which are indigenous to the United States. It is the purpose of this manuscript to show the sources and value of these enemies and to indicate how they may be utilized to the advantage of the farmers of the cotton belt. I recommend the publication of this manuscript as Bulletin No. 100 of the Bureau of Entomology. Respectfully, L. O. Howard, Entomologist and CJiief of Bureau. Hon. James Wilson, Secretary of Agriculture. CONTENTS. Page. lutroductiou 9 Conduct of the parasite project 10 Historical data H Scope of present report 12 Part I. The status of the cotton boll weevil and its enemies. 1. A general chronological study of the insect control of the boll weevil. . 13 2. Nature and sources of the material examined 14 3. Seasonal studies of insect control, by class of infested material 14 4. A geographic study of the statistics of insect control 20 5. A study of the share of insect control in the mortality of immatui-e Ixill weevils 22 6. A study of how agriculture modifies insect control 30 7. Climatic considerations 32 8. How insect control follows the dispersion of the boll wee\il 35 9. The status of the boll weevil and its control by insects 37 10. A brief statement of the various classes of control exercised uj^on the boll weevil 38 11. Practical conclusions derived from statistical studies 38 Part II. Biological complex. 1. A list of the insect enemies of the cotton boll weevil 40 2. The hosts of boll-weevil parasites 42 3. Mites which attack the boll weevil 43 4. Flies which parasitize the boll weevil 47 5. The hymenopterous parasites of the boll weevil 48 G. Biological notes upon the parasites of the weevil 54 7. The develojament of the parasites 57 8. The distribution of the parasites 61 9. The parasite seasons 62 10. Adjustment to new hosts 66 11. Beetles which prey upon the boll weevil 68 12. Lepidopterous larva- which are incidentally predatory upon the boll weevil 69 13. Ants which prey upon the boll weevil 69 14. Biology of the cohosts of the boll-weevil i^arasites 73 15. A list of the host plants of the cohost weevils 80 16. A summary of the more important biological facts 82 Part III. The economic application. 1. The economic principles involved 83 2. Interpretation of parasite statistics 85 3. Interpretation of the biological complex 86 4. How to i^rofit by existing conditions 86 5. How to plan for the greatest possible control -90 6. Propagation and artificial introductions 91 7. Objectionable practices 93 8. The economic significance of the investigation 94 Bibliography 97 5 ILLUSTRATIONS. PLATES. Page. Plate I. Shedding and retention of forms on the cotton plant. Fig. 1. — Normal scars left by shed forms. Fig. 2. — Abnormal scars with forms retained. Fig. 3.— Longitudinal section through base of retained form IG II. Eggs of boll-weevil parasites. Fig. 1. — Mierodontonicrus anthonomi. Fig. 2. — Unidentified egg. Fig. 3. — Cerambycobiiis cyaniceps. Fig. 4. — Eurytoma tylodermatis. Fig. 5. — Catolaccus hunter i. Fig. 6. — Unidentified egg 56 III. Parasites of weevils. Fig. 1. — Eurytorna tylodermatis, Tpu^pa. Fig. 2. — Catolaccus incertus, pupa. Fig. 3. — Cerambycobiiis cyaniceps, pupa. Fig. 4. — Microdontomerus anthonomi, pujaa. Fig. 5. — Larva of Microbracon. Fig. G. — ilicrobraconmellitor, \:)upa. Fig. 7. — Larva of chalcidoid 56 TEXT FIGURES. Fig. 1. Diagram illustrating the monthly percentage of mortality of immature boll weevils due to insect enemies 19 2. Diagram illustrating the average climatic and insect control of the immature boll weevils during 190G, 1907, 1908, and 1909, in hanging squares 21 3. Diagram illustrating the average climatic and insect control of the immature boll weevils during 1906, 1907, 1908, and 1909, in fallen squares 22 4. Diagram illustrating Texas climatic variations in 1907, 1908, and 1909. 36 5. Diagram illustrating Louisiana climatic variations in 1907, 1908, and 1909 37 6. Diagram illustrating the boll-weevil complex 44 7. Diagram giving the parasites of the boll weevil and their other hosts . 45 8. Pediculoides ventricosus: Adult female, before and after inflation of abdomen with eggs and young 46 9. Microdontomerus anthonomi: Adult 49 10. Habrocytus piercei: Pupa 52 11. Sigalphus curculionis: Male, female, antenna 53 12. Microbracon mellitor: Adult 54 13. Diagram illustrating yearly rank of the boll-weevil parasites, 190G, 1907, 1908, and 1909 62 14. Map showing the distribution of the more important parasites of the boll weevil 63 15. Diagram illustrating the seasonal rotation of hosts of Catolaccus hunteri and Cerambycobius cyaniceps 67 16. The "fire ant " {Solenopsis geminata): Worker 70 17. The little black ant (J/onoHionMmmmmm/i): Adult, egg, larva, pupa . 71 6 INSECT ENEMIES OF THE BOLL WEEVIL. 7 Page. Fig. 18. The little red ant {Monomorium pharaonis): Female and worker 72 19. The coffee-bean weevil {Araecerusfasciculatus): Adult, larva, pupa. .. 74 20. The blood weed weevil {Lixus scrobicoUis): Adult 75 21. The ironweed weevil {Desmoris scapalis) : Adult 76 22. The pepper weevil {Anthonomus eugenii): Adult 77 23. The cowpea weevil {Chalcodermus seneus): Adult 78 24. The plum curculio {Conotrachelus nenuphar): Larva, adult, pupa 78 25. The potato-stalk weevil {Trichobaris trinotata): Adult, larvae, pupa3.. 79 26. The rice weevil {Calandra oryza): Adult 80 THE INSECT ENEMIES OP THE COTTON BOLL WEEVIL. INTRODUCTION. Wlaen the cotton boll weevil first entered the United States it appeared to have almost undisputed sway. It did, in fact, escape most of its enemies. But whether parasites were introduced with it or not, we now know that within the first three years of its existence in Texas it was attacked by three important species of parasites. Year after year new factors in its control are becoming apparent, although some have probably been concerned since the beginning. On the other hand, it is certain that entirely new elements are entering the struggle as rapidly as the weevil enters new biological complexes. Among the most striking of these new elements in the control is the recent adjust- ment of Microdontomerus anthonomi Crawford (fig. 9, p. 49) . This spe- cies was unknown until 1906 when a very few were taken in material reared at Cuero, Goliad, Hallettsville, Victoria, and Waco, Tex. In 1907 it was found to predominate in a portion of central Texas. In 1908 its range was found to extend northward to the Red River. In 1909 it was found as far east as the Mississippi River in Louisiana. Only a single record of the occurrence of Sigalplius curculionis Fitch (fig. 11, p. 53), the common parasite of the plum curculio, had been made prior to 1908. In that year it began to make its presence felt in northeastern Louisiana and western Mississippi. In 1908 a new chalcidoid parasite, recently described as Tetrastichus Imnteri Crawford, was found to be the leading parasite of the boll weevil in northern Louisiana and western Mssissippi. In 1909 this species was found as far west as Arlington, Tex. With the advent of each new enemy and its more complete adjust- ment, the power for damage possessed by the weevil is by so much diminished. On the other hand, every factor which checks these enemies without also checldng the weevil benefits the weevil. If the solution of the boll-weevil problem consisted merely in addmg, one by one, factors wliich would cut off a given percentage of the weevils, the time would not be distant when that might be accom- pHshed. The problem is far more comphcated. The various factors do not discriminate against one another, for wlfile lieat, ants, cold weather, and excessive moisture may remove many parasites from the struggle, it also foUows that heat, cold weather, heavy rains, 9 10 INSECT ENEMIES OF THE BOLL WEEVIL. predators, and other pests remove many ants. Proliferated plant tissue frequently acts as an important check upon the weevil, and yet in many cases it serves as a food for the weevil rather than as a con- trolhng force. Moist weather aids the weevil. The leaf-worm, while cutting off most of the weevil food, finally is checked by parasites. Light, heat, and dryness favor certain parasites, whereas shade and moisture favor others. Parasites that are normally primary fi-e- quently waste their energies by accidentally becoming secondary, and normally secondary parasites, and probably tertiary as well, also enter the consideration. Predatory enemies fail to distinguish the parasites from the weevils, but are in turn held in check by their own enemies. The birds devour weevils, predators, and parasites, but they in turn are kept down by other bu'ds and even man himself, and thus the complexity grows. There are 49 species of insects which attack the immature stages of the boll weevil. Of these insects 29 species may be classed as para- sitic, 5 as predatory larvse, and 15 as predatory adults. They are divided among the orders, with 3 in the Acarina, 4 in Coleoptera, 36 in Hymenoptera, 5 in Diptera, and 1 in Lepidoptera. One of the acarians, 1 coleopteron, 15 Hymenoptera, and 1 dipteron, may be considered as quite important. A weighted average mortality of 3.93 per cent of all immature stages may be accredited to the com- bined factors of all parasitic enemies; the predators are responsible for 15.93 per cent, while climate is responsible for 24.45 per cent, and plant proliferation 12.42 per cent. This makes the total natural control of immature stages 56.73 per cent. In addition to the insects attacking the boll weevils in the squares, there must be considered the insects which prey on the adults. These include one praying mantis, one predaceous bug, two beetles, and two ants — six species in all. This bulletin is not concerned with the mortality of the weevils after they become adult because reliable figures can not be gathered upon this point. It is certain that many weevils fall prey to preda- ceous insects and to birds, and the well-known habits of the horned lizard would include it in the list of possible enemies. The important fact is that 56 per cent of the weevil eggs fail to produce adult weevils. The remainder is still a formidable number but the many adverse influences continue to operate upon the adults and likewise upon their progeny. CONDUCT OF THE PARASITE PROJECT. The investigation of the insect enemies of the cotton boll weevil was initiated in 1 905. It has been conducted from the beginning by the senior author under the direction of Mr. W. D. Hunter, and with HISTORICAL DATA. 11 the direct influence and encouragement of Dr. L. O. Howard, Chief of the Bureau of Entomology. Messrs. R. A. Cushman and C. E. Hood have been intimately associated in the preparation of the material for this bulletin since 1907. The collecting, examining, and recording of the immense mass of material has involved in addition the services of Messrs, E. A. Schwarz, J. D. Mitchell, W. E. Hinds, Wilmon Newell, F. C. Bishopp, A. C. Morgan, F. C. Pratt, C. R. Jones, W. W. Yothers, G. D. Smith, A. H. Rosenfeld, H. S. Smith, E. S. Tucker, T. C. Barber, S. Goes, C. S. Spooner, C. W. Flynn, T. C. Paulsen, J. A. Hyslop, V. I. Safro, T. E. Holloway, H. Pinkus, W. H. Hoffman, F. L. Elliott, and O. M. Lander. Considerable credit is due Messrs. E. A. Schwarz, J. C. Crawford, W. M. Wheeler, D. W. Coquillett, and C. H. T. Townsend for determination of the insects concerned. The weevils entering the biological complex have been determined by the senior author. In short, 33 entomologists have directly contributed the data which are herewith presented. HISTORICAL DATA. The first definite records of the parasites of the cotton boll weevil were made by C. H. T. Townsend in 1895 when he mentioned a small hymenopterous parasite and also recorded the suspicious occurrence of several species of Scymnvs in the squares, and mentioned that a fungoid parasite, a species of Cordyceps, "was found growing out of a dead pupa in its cell in a boll, November 26, in a field in San Juan Allende, Mexico." (Townsend, 1895.) In 1901 Profs. Herrera and Rangel published notes concerning the parasitic attack of Pedi- culoides ventricosus Newport (fig. 8, p. 46) upon the boll weevil (Rangel, 1901b, 1901c). In 1902 Dr. Wm. H. Ashmead described Bruchophagus herrerx from Coahuila, Mex., as a primary parasite of the boll weevil (Ashmead, 1 902a, 1902b ; Herrera, 1 902a) . This is iprohoMy Eurn/toma tylodermatis Ashmead. Prof. Herrera also recorded the activities of a predaceous ant, Formica fusca Linn., subspecies suhpolita Mayr, variety jjerpilosa Wlieeler, (Herrera, 1902b; Wlieeler, 1902). In the same year Prof. F. W. Mally recorded the fact that Bracon (now Microhracon) mellitoi' Say (fig. 12, p. 54) and Eupehnus (now Cerambycohius) cyaniceps Ash- mead had been reared by him, since 1899, in considerable numbers from the boll weevil. He also recorded a species of Eurytoma. (Mally, 1902.) In 1904 Hunter and Hinds recorded additional primary parasites as follows: Sigalphus curculionis Fitch (fig. 11, p. 53), Catolaccus incertus Ashmead, Urosigalphus (rohustus Ashmead), Bracon (dorsator Say), and Eurytoma tylodermatis Ashmead, as well as an entomog- enous fungus, Aspergillus (Hunter and Hinds, 1904). The Urosi- 12 INSECT ENEMIES OP THE BOLL. WEEVIL. galplius has since heen described as Vrosigalphus antlwnomi Crawford (Crawford, 1907a). In 1906 Mr. Nathan Banks described a mite, Tyroglyphus Ireviceps, collected at Victoria, Tex., from boll-weevil larvoe (Banks, 1906). In 1907 the senior author of this bulletin added Hydnocera pubescens LeConte as a predaceous enemy of the boll weevil (Pierce, 1907a, 1907b, 1907c). In the same year Dr. Hinds published two papers in which the work of SolenojJsis geminata Fab. (fig. 16, p. 70), variety xyloni McCook, as a predator on the boll weevil was fully discussed, and considerable statistical data on the parasitic control of the weevil were presented (Hinds, 1907a, 1907b). Mr. Morgan published a brief account of the predatory attack of a bug, Apiomerus spissipes Say (Morgan, 1907). Mr. J. C. Crawford described as parasites of the boll weevil Torymus antlionomi, Urosigalphus anthonomi, and UrosigalpJius schwarzi (Crawford, 1907a). In 1 908 the senior author of this report recorded Catolaccus antho- nomi Ashmead as a boll- weevil parasite and Cathartus cassise Reiche (gemeJlatus Duval) as a predator (Pierce, 1908a, 1908b, 1908c, 1908d). Mr. Crawford described Ceramhycohius cushmani and Catolaccus Jiunteri as new parasites of the boll weevil (Crawford, 1908). During the same year two new predaceous enemies of the boll weevil were recorded from Louisiana, namely, Evartlirus sodalis LeConte and Evartlirus sp. (Newell and Trehearne, 1908). Mr. Townsend, in a paper on the muscoidean flies, recorded Ennyomma glohosa Townsend as a parasite of the boll weevil (Townsend, 1908). During 1909 Mr. Crawford described Tetrastichus liunteri as a parasite of the boll weevil (Crawford, 1909b). SCOPE OF PRESENT REPORT. The present report is supplementary to a former bulletin which was based on investigations prior to 1907 (Pierce, 1908a). The matter contained herein has mainly been gathered during the years 1907, 1908, and 1909. Only such notes as are of value for the sake of comparison have been repeated from the previous report. The work is divided into three parts : I. The status of the cotton boll weevil and its enemies. II. The biological complex. III. The economic application. PART I. THE STATUS OF THE COTTON BOLL WEEVIL AND ITS ENEMIES. Part I of this bulletin shows the large mass of statistical material gathered during the four years of the parasite investigation, and attempts to place this material in such form as to show its economic value and significance. CHRONOLOGICAL STUDY OF INSECT CONTROL. 13 The matter is arranged topically as follows: 1. A general chronological study of the insect control of the boll weevil. 2. The nature and sources of the material examined. 3. Seasonal studies of the insect control by class of infested material. 4. A geograpliical study of the statistics. 5. A study of the share of insect control in the mortality of imma- ture weevils. 6. A study of how agriculture modifies insect control. 7. Climatic considerations. 8. How insect control follows the weevil dispersion. 9. The status of the boll weevil and its control by insects. 10. A brief statement of the various classes of control exercised upon the weevil. 11. Practical conclusions derived from statistical studies. 1. A GENERAL CHRONOLOGICAL STUDY OF THE INSECT CONTROL OF THE BOLL WEEVIL. Kecords upon parasitic control of the boll weevil begin in July, 1902, and occur more or less scatteringly until June, 1906. The records of 1906 were very extensive, but, as will be shown, the}^ were merely preliminaiy . Table I is arranged to show the extent of the examinations made since 1902. This table should not be used to compare the records of the various years, as the manner of investigation in each year has been different, and the sources of the material have varied greatly. The table is only intended to show the total of the examinations and how these were distributed from year to year. A careful analysis of the figures has been given in the various sections of Part I. Table I. — Insect control of the boll weevil, by years. 1902. 1903. 1905, March.. 1905, August. 1900 1907 1908 1909 Totals and averages . Weevil stages. 602 819 1,005 1,702 40, 073 13, C02 29,349 11,653 98, 805 Preda- tors. (?) (?) (?) (?) 10,547 2,279 3,862 1,231 I'ara- sites. 59 32 21 1,728 1,121 2,952 020 6,540 Per cent mortality due to— Preda- tors. (?) (?) (?) (?) 26.31 16.75 13. 15 10. 56 Para- sites. 1.16 7.20 3.18 1.23 4.31 8.24 10.05 5.32 1 6. 61 All insects. (? (?) (?) (?) 30. 62 24.99 23.20 15.88 1 This table should not be construed as indicating that parasite control has been falling oft, because the table is based upon different kinds of examinations in difierent years. The detailed analysis of these records will be found on subsequent pages. 14 INSECT ENEMIES OF THE BOLL WEEVIL. The figures of 1902 are based on the total number of stages reared. The data of 1903 are based on the total number of stages reared, but mclude both stages in hanging and fallen forms. There were 654 stages in fallen forms of which 14, or 2,14 per cent, were parasit- ized, and 165 stages in hanging forms of which 45, or 27.27 per cent, were parasitized. The figures of 1905 were separated to show the investigations of March and August because of the great difference in the mortality from parasites in these two months. Between 1906 and 1909 the data represent all classes of infested material and all infested regions. It will be noticed that for the last four years the total insect control of the immature weevils has fluctuated between 15 and 30 per cent. 2. NATURE AND SOURCES OF THE MATERIAL EXAMINED. During the four years 1906-1909 examinations of mortality have been made of material collected at 6 places in Arkansas, 26 in Louisi- ana, 6 in Mississippi, 7 in Oklahoma, and 65 in Texas, making a total of 110 places. These examinations are based upon 94,677 stages, involving an individual examination of over 222,700 cotton forms (squares, blooms, and bolls). Many other collections and exami- nations were made, but because of incomplete records are excluded from the accompanying tables. During the four years there has been the equivalent of examina- tions in 176 localities, or an average of 44 localities per year. 3. SEASONAL STUDIES OF INSECT CONTROL, BY CLASS OF INFESTED MATERIAL. Very shortly after the work began in 1906 it became evident that the activity of the parasites and other insect enemies of the weevil was very difi'erent in squares and bolls, and in fallen or hanging squares or bolls, and also that the highest control by parasites was in hanging squares. An examination of the squares of various varieties of cotton plants will show the observer that certain ones have a transverse attachment of the pedicel to the stem. In all cases where this attachment is perfectly transverse, the square when injured by any insect is caused to drop because of the separation of the infested part from the main stalk by the growth of an absciss layer at the point of attachment. (PI. I, fig. 1 ; fig. 3, a.) Certain other varieties indicate a long diag- onal attachment to the stem. Wlien these squares are injured, a diagonal absciss layer is formed which runs down the stem from one- half to three-fourths of an inch or even more. This layer is gen- erally incomplete at the lower point and consequently the square SEASONAL STUDIES OF INSECT CONTROL. 15 hangs by a few threads and dries on the plant. (PI. I, fig. 2 ; fig. 3, &.) To these squares and bolls which thus hang, we have applied the terms ''hanging squares" and "hanging bolls." Tables II and III, which are arranged to show the monthly per- centages of control by parasites, by predators, and by all insects, illustrate the differences in the control of the weevil in the four principal classes of infested material, namely, fallen and hanging dry squares, and fallen and hanging dry bolls. A few words of explanation of these tables are necessary in order to show what is meant by the different classes of mortality. It has been found that a large number of stages are destroyed as eggs or young larvae by the proliferation of the plant tissues. At the time of the examination for mortality of the weevil, all evidence of the weevils destroyed in these stages has disappeared; consequently the percentages of mortality given in the following tables are tlie per- centages of stages found which arc killed by the causes enumerated, and the mortality from proliferation is entirely ignored. Table II. — Monthly viortality of the boll weevil due to insects in fallen squares. Month. June July August . . . . September. October Totals and avora,i,'''s for 1906 June July August November. 1907 Totals and averages for 1907 May June July August September. October November. Totals and averases for 1908 January . . . July August September. Totals and averages for 1909 Squares exam- ined. 4,176 7,265 V.),?.05 l;),70!) l.ilSl 43,736 2,074 5,192 7,400 150 14,S16 100 7,808 7,437 1,941 7,189 9,678 604 34, 757 50 ,677 ,507 750 13,984 Stages. foimd. 3,831 4,552 11, 186 5,365 600 25,534 1,261 3, 60S 5,058 93 10,020 56 5,285 4,690 1,208 3,894 5,342 369 20,844 23 4,334 2,866 364 7,587 Stages killed hy — Cli- mate. 1,797 1,676 2, 8?S 1,475 205 7,981 339 778 2, 156 90 3,363 4 1,169 1,{)47 540 578 807 90 Preda- tors. 914 1,079 4,097 1,625 133 7, 848 198 433 1,372 2,003 866 902 294 815 289 1 4,235 3,167 1,318 680 19 507 428 940 Para- sites. lis 207 ISO 285 33 823 76 133 155 1 2 324 219 63 136 659 131 Percentage of stages killed. Tofal. 73. S 65. 1 63.5 63.0 61.8 48.6 37.2 72.8 97.7 10.7 44 6 46.2 74.2 39.2 32. S 51.1 42.7 45. 1 39.9 6.8 Preda- tors. 23.8 23.6 36.6 30.2 22.1 1.5.6 11. 9 27.1 19.9 16.4 19.2 243 20.9 5.4 2.7 15.2 11.7 14 9 1.4 Para- sites. .3.1 4 7 1.7 5.4 5.6 3.3 7.0 3.8 .3.0 1.0 3.5 6.1 4 7 5.2 3.5 12.3 22.6 3.0 1.3 .3 2.2 All insects. 26.9 28.3 38.3 3.5.6 27.7 22.6 15.7 30.1 1.0 3.5 22.5 23. 9 29.5 24 4 17.7 25.3 14 7 1.5.2 1.7 14 6 16 INSECT ENEMIES OF THE BOLL WEEVIL. A study of Table II, on the mortality due to insects in fallen squares, shows that the principal insect work is that of predatory insects and, furthermore, that the total insect control is, as a rule, less than the climatic control. The table embraces the examination of 63,985 weevil stages of which 17,596 were killed by climate, 13,958 by predators, and 2,849 by parasites. In other words, the average percentage of control in fallen squares by all kinds of insects is 26.2 per cent, or 21,8 per cent by predators and 4,4 per cent by parasites. A further study of Table II shows that the predators have in each year done their most valuable work in the month of August. The parasites, however, have shown considerable variation in the month of their best work. In 1906 the highest average percentage was in October; in 1907 it was in June; in 1908 in November; and in 1909 in July. Table III. — Monthly mortality of the boll weevil due to insects in hanging squares. Squares exam- ined. Stages found. Stages killed by- Percentage of stages killed. Months. Cli- mate. Preda- tors. Para- sites. Total. Preda- tors. Para- sites. All in- sects. 1906 July 474 4, 105 2, 032 33 247 2,566 1,285 20 47 539 245 4 20 544 269 10 76 337 125 57.9 55.3 49.7 70.0 8.0 21.2 20.9 50.0 21.0 13.1 9.7 29.0 34.3 30.6 October 50.0 Totals and averai:;es for 1906 6, 704 4,118 835 843 538 53.8 20.5 13.0 33.5 1907 150 956 3,543 88 513 2,011 26 57 296 5 16 175 13 103 580 50.0 34.3 52.2 5.7 3.1 8.7 14.7 20.1 28.8 20.4 July 23.2 37.5 Totals and averages for 1907 4,649 2,612 379 196 696 48.6 7.5 26.6 .;4.i 190S July 2,955 1,393 3,922 1,192 1,125 2,177 842 2,340 553 10 395 141 476 116 8 179 91 259 53 479 279 410 113 48.4 60.7 48.9 52.9 80.0 8.2 10.8 11.0 10.0 22.0 33.1 17.5 21.2 30.2 43.9 September 28.5 October 31.2 Totals and averases for 1908 10,587 5,922 1,136 582 1,281 50.9 9.8 21.7 31.5 1909 80 630 1,290 745 136 515 3 383 856 496 52 169 36 96 61 14 47 31 72 21 1 117 88 76 30 71 48.0 29.9 31.9 100. 70.4 8.1 8.4 4.2 6 30.5 10.3 15.3 68.0 42.0 July 38.6 August 18.7 19.5 68.0 December 42.6 Totals and averages for 1909 3,396 1,959 254 125 382 38.8 6.4 19.5 25.9 Table III shows that the principal insect work in hanging squares is that of parasitic insects and, furthermore, that the total insect control in hanging squares is each year higher than the climatic control. Tliis table embraces the examination of 14,611 weevil I. 100, Bureau of Entomology, U. S. Dept. of Agricultu Plate I. Shedding and Retention of Forms on the Cotton Plant. Fi.L(. 1.— a, b, c. Normal scars left by shed forms. Fig. 2.— o, 6. '■, Atmormal .sears witli forms retained. Fi,?. 3.— «, Longitudinal section through base of .shed form; b. Longitudinal seotio7i throu.sh base of retained form. Fig. 1, natural size: fig. 2. ,v<)me\vhat reduced: fig. 3, enlarged two diameters. (After Hinds.) SEASONAL STUDIES OF INSECT CONTROL. 17 stages of wliich 2,604 were killed by climate, 1,746 by predators, and 2,897 by parasites. In other words the average percentage of control by all lands of insects is 31.61 per cent, or 11.93 per cent by predators and 19.68 per cent by parasites. It appears that July and August are usually the best months for parasite control in hang- ing squares. Table IV. — Monthly mortality of the boll weevil due to insects in hanging bolls. Bolls exam- ined. Stages found. Stages killed by- Percentage of stages killed. Months. Cli- mate. Preda- tors. Para- sites. Total. Preda- tors. Para- sites. Allm- sects. 1906 145 2,947 23, 454 6,210 399 290 2,977 1,555 147 28 416 198 21 14 742 188 11 19 23 3 0.0 14.5 39.5 26.3 23.8 0.0 4.8 24.9 12.1 7.5 0.0 .0 1.5 2.0 0.0 July 4.8 25.5 13.6 9.5 Totals and averages for 1906 33,155 4,969 603 955 45 35.9 21.9 0.9 22.8 1907 50 60 1,272 5 7 330 1 1 115 51 1 4 40.0 14.3 51.5 15.4 20. 1.2 20.0 July 16.6 Totals and averages for 1907 1,372 342 117 51 5 50.6 14.9 1.4 16.3 1908 2,227 4,450 1,123 933 238 405 200 98 34 125 22 6 26 20 4 21 13 1 29.7 40.5 21.0 13.2 2.5 6.4 10.0 4.1 8.8 3.2 1.0 11.3 July 9.6 10.0 5.1 Totals and averages for 1908 8,733 941 189 56 35 29.7 5.9 3.7 9.6 1909 1,616 716 608 402 115 56 133 12 14 25 49 12 11 2 1 42.0 54.7 48.2 6.2 42.6 21.4 2.7 1.7 1.7 8.9 44.3 March 23.1 Totals and averages for 1909 2.940 573 159 86 14 45.2 15.0 2.4 17.4 In fallen bolls the principal insect work is that accomplished by predatory insects, and the total insect control has been less than the climatic control except in the year 1906. Table IV covers an examination of 6,825 weevil stages, of which 1,128 were killed by climate, 1,148 by predators, and only 99 by parasites. Tliis means that 18.2 per cent of all the stages were killed by insects, or 16.8 per cent by predators and 1.4 per cent by parasites. In this class of infested forms it is also noticeable that the principal work by the predators is accomplished during the month of August. 16844°— Bull. 100—12 2 18 INSECT ENEMIES OF THE BOLL WEEVIL. Table V. — Monthly mortality of the boll weevil due to insects in hanging bolls. Bolls exam- ined. Stages found. Stages killed by- Percentage of stages killed. Month. Cli- mate. Pred- ators. Para- sites. Total. Pred- ators. Para- sites. All insects. 1900. July 43-1 S, 702 4, 22 1 it, 029 22 2,444 1,627 1,359 2 281 i;5o ISO 3 340 2.»2 2i;6 155 111 I 06 22.0 31.7 32.1 38.2 13. 13.9 17.9 19.0 0.0 6.3 0.2 4.8 13.6 .\ugust 29.2 24.1 October 24.4 Totals and averages for 1906 17,049 5,452 599 901 322 33.4 10.5 5.9 22.4 1907. July 460 683 38 393 2 35 13 50 5.3 25.0 3.0' 12.5 August.. 16.1 Totals and averages lor 1907 1,143 431 37 13 50 23.2 3.0 11.6 14.6 1908. February 12.451 1,239 2, 132 720 664 432 519 515 22 492 191 83 262 274 424 21 03 23 7 36 134 37 7 17 11 1 54 1 58 22 5 8 92.8 100.0 32.0 27. 2 .31 ! 3 19.8 52.2 7. 5 3.0 20. 4 4.2 .3 10.5 4.5 11.7 11.5 2.4 1.9 2.9 10.5 4.5 July 19.1 August.. 15.1 September 22.8 6.1 November. . 3.2 Totals and averages for 190S 18,157 1,839 708 73 150 50.6 3.9 8.1 12.0 1 909. January 3,941 430 053 365 2,148 8.57 ;« 81 42 519 335 13 16 1 217 38 11 10 13 43 11 48.5 68.6 39.5 8.1 46.4 4.4 31.4 19.7 5.4 25.0 5.0 2.1 9.4 February. . 31.4 March 19.7 August 5.4 December 27.1 Totals and averages for 1909 7,537 1.5.34 582 SO 54 46. 7 5.2 3.5 8.7 SEASONAL. STUDIES OF INSECT CONTEOL. 19 Table V was based, as may be seen, upon the examination of 9,256 weevil stages, of which 1,926 were killed by climate, 1,067 by pred- ators, and 576 by parasites. In other words, the insect enemies killed 17.74 per cent, of which 11.52 per cent were killed by predators and 6.22 per cent by parasites. July and August are the principal months for attack upon hanging bolls. Summarizing the four preceding tables, Table VI is presented to show the monthly rate of mortality in all classes of infested forms. Fig. 1.— Diagram illustrating the monthly percentage of mortality of immature boll weevils due i insect enemies. (Original.) It will be noticed that in each year certain months have been omitted and it must be explained that the reason therefor has been the necessity of making these examinations only when other work was not pressing. An analysis of this table is more readily made by reference to the accompanying diagram (fig. 1), wliich demonstrates conclusively that August is the month during wliich the insect enemies of tlie boll weevil are most active. 20 INSECT ENEMIES OF THE BOLL WEEVIL. Table VI. — Monthly rate of inortalitij of the boll weevil in infested forvrs of all classes Month. 1906. •Tune July August September October Totals and averages for 1906 1907. June July August November Totals and averages for 1907 1908. February March May June July August September October November Totals and averages for 1908 1909. January February March July August September November December Totals and averages for 1909 Forms exam- ined. 4,621 11,120 55,686 2.3,175 6,042 100, 644 2,274 6.658 12, 898 150 21,980 12,451 1,329 100 10, 035 16, 974 5.177 12,708 11,302 2,248 .234 5.087 1,146 1,261 8. 307 7,162 1,495 136 2, 663 27,857 Stages found. 3,831 5,111 19,173 9,832 2,126 40, 073 1,354 4, 166 7, 792 93 13,405 515 22 56 5,523 7,764 2,441 6,415 6. 157 053 29,546 1,285 150 137 4,717 3, 764 860 52 688 11,653 Percentage of stages killed by- All causes. 73.80 61.67 54.64 50.40 44.12 55.81 48.67 36.55 64. 19 97.70 54.27 92.81 1(10. 00 10.70 43.81 45.63 61.53 42.29 33. 92 50. 53 44.34 45.52 58.00 43.06 45. .36 37. .32 21.25 100. 00 52. 32 41.73 Clmiate. 46. 90 34. 29 21.19 20.80 19.56 25.15 27.03 20.11 33.39 96.70 29.06 82.33 95.50 7.20 15.78 20.99 29.79 16. 66 15.57 35.52 21.21 36. 42 16. 06 21.89 28. 70 20.64 9. .30 32. 00 38.37 Preda- tors. 23.80 21.83 29.32 24.14 19.75 26.31 14.99 10.77 20.67 16.88 15.78 14.73 16.87 17.06 5.73 3.06 13.12 4.90 40.00 20.43 11.19 13. .33 3.02 2.03 25.84 10.56 Para- sites. 3.10 5.53 3.61 5.43 4.79 4.31 6.64 5.68 10.12 1.00 8.32 10.48 4. .50 3. 50 6.24 9.90 14.91 8.55 12.61 14.70 10.00 4.20 1. .33 .72 5!25 3.34 8.95 68.00 11.91 5.32 All insects. 26.90 27.36 32.93 29.57 24.54 30.62 21.63 16.43 30.79 1.00 25.20 10.48 4.50 3.50 22.02 24.63 31.78 25.61 IS. .34 17.76 23.12 9.10 41.33 21.15 16.34 16.67 11.97 68.00 13.94 15.88 4. A GEOGRAPHIC STUDY OF THE STATISTICS OF INSECT CONTROL. A study of these same statistics, when arranged to show the insect control by States, has given much interesting Ught upon the subject of the control of the weevil. In fallen squares we find an average for total insect control of 26.8 ])er cent in Oldahoma, 25.9 per cent in Mississippi, 24.5 per cent in Texas, 20.6 per cent in Louisiana, and 12.5 per cent in Arkansas. Anal3^zing these figures from another standpoint, we find that the State of Mississippi leads in parasite control with 14.27 per cent, Oklahoma standing next with 4.71 per cent, Texas with 3.9 per cent, Louisiana with 2.52 per cent, and Arkansas with 0.71 per cent. The relative rank of the States for predatory control is quite different. Oklahoma leads with 22.16 per cent, Texas comes next with 20.6 per cent, Louisiana with 18.1 per cent, Arkansas with 11.82 per cent, and Mississippi with 11.63 per cent. In climatic control Texas leads GEOGEAPHIC STUDY OF STATISTICS. 21 with 37.9 per cent, Oklahoma comes next with 30. S per cent, Arkan- sas with 25.65 per cent, Louisiana with 12.5 per cent, and Mssissippi with 11.7 per cent. Thus it may be seen that the dry, prairie States of Texas and Oklahoma lead in the climatic and predatory control of the weevil and also in the total amount of control, and that the climatic control in each of these States is greater than the total insect control. Tliis latter fact is also true of Arkansas. In Louisiana and Mississippi, States which are naturally more humid, the chmate has less influence and the greater proportion of the control is by the insect enemies. In hanging squares the conditions are entirely reversed. It is noticeable that Oldahoma leads in parasitism with an average of 31.74 per cent, Texas averages 2G.6 per cent, Arkansas 24.16 per cent, Mis- sissipi 21.2 per cent, and Louisiana 12.07 per cent. In predatory control Louisiana leads with 12.9 per cent, Texas comes next with 10.9 /O 20 30 -^ SO 60 /2.07 12.9 /S.69 \ 40.66 30 69 1 \ = c. ^RASITES lEDATORS './MATE LOU/S/ANA HBflHH mmm^mA ^a^^L e.38 8./ 2 M/SSrSSIPPI MH^^^^r \36. — 3/. 74 2. S3 26. ARKANSAS WKM- \S3.38 JO. 9 /6.8 TEXAS iHUIL^ W////A \54.3 9.53 OKLAHOMA HHHHHH iH ~\4/.27 Fig. 2.— Diagram illustrating the average climatic and insect control of the immature boll weevils during 1906, 1907, 1908, and 1909, in hanging squares. (Original.) per cent, Mississippi with 6.98 per cent, and Arkansas with 2.53 per cent. We have no record of predatory control in Oklahoma. In all five States insect control in hanging squares is greater than climatic control. With regard to climatic control Arkansas leads with 26.69 per cent, Texas has 16.8 per cent, Louisiana 15.89 per cent, Oldahoma 9.53 per cent, and Mississippi 8.12 per cent. These statistics are graphically shown in figures 2 and 3. A brief comparison of the condition in hanging and fallen squares will show that the States of Texas and Oklahoma have a higher average percentage of control from all factors in fallen squares than in the hanging squares ; the States of Louisiana and Arkansas have a higher average percentage of control from all factors in hanging squares than in fallen squares, and in the State of ^Mississippi the difference is very slight, although in favor of the fallen squares. This illustrates the 22 INSECT ENEMIES OF THE BOLL WEEVIL. difficulty of giving any single recommendation for the control of the boll weevil whicli would apply to all regions. This i)oint wiU be brought out more fully in other sections of this bulletin. 5. A STUDY OF THE SHARE OF INSECT CONTROL IN THE MORTALITY OF IMMATLTRE BOLL WEEVILS. The condensed tables which have been presented are likely to give the impression that the parasite control of the weevil is on an average very low, but it must be remembered that the examinations have been made in all parts of the infested region whether the weevil has been present 17 years or only a few months, and whether the weevil damage amounts to less than 1 per cent of the crop or to almost 100 ARKANSAS LOU/S/A/\JA TEXAS, OKLAHOMA M/SS/SS/PPl\ PER CENT /a ^0^ 30 40 SO 60 0.7> L II. 82 2S.65 8.18 37.9 1 \ = a.//^ArE im^////yf; ^ \3 2.52 I 18.1 /2.S i^^ W///////A 1 Z333./2 3.9 20.6 k^^^ ^^//y^m^/A WA _\62.4 4.7/ 22./ 6 30.8 Z67 [■III W////////A 'f/////A \5 /^.2; ' // 63 //.7 7.60 wammtmmv//////y. mm \3 Pig. 3. — Diagram illustrating the average climatic and insect control of the immature boll weevils during 1906, 1907, 1908, and 1909, in fallen squares. (Original.) per cent. This great difference in the sources of the inaterial exam- ined has necessarily lowered the average mortalitj" to its minimum. Tlie following records show some of the cases of very high mortality due to parasites: Highest records of parasitism of the hoU weevil. IN FALLEN SQUARES. liOealif V. Date. Number of stages. Percent- age of parasit- ism. Robson,La Corpus Christi, Tex Natchez, Miss Dallas, Tex GoUad, Tex Natchez, Miss Cuero, Tex Natchez, Miss Shreveport, La Victoria, Tex Roosevelt, Tex Arlington, Tex Brownsville, Tex. . . Denison, Tex Atoka, Okla Nov. 5, 1907. June 20, 1907. Oct. 23, 190S. Aug. 12, 190S, July 28, 1908. Oct. 16, 1908. Aug. 12, 1907. Julv, 1909... Oct. 29, 1908. June 19, 1908. Sept. 24, 1900 July 17, 1908. Sept. 5, 1906., July, 1909.... Sept. 2, 1908.. 53 92 157 IS 114 230 105 200 624 513 69 382 ,147 494 100 77.36 36.95 28.6 27.78 26.63 21.7 19.04 18.5 15.8 14.5 14.4 13.35 12.4 8.5 8.0 SHAEE OF INSECT CONTROL IN WEEVIL MORTALITY, 23 Highest records of parasitism of the boll weevil — ("outiuued. IN HANGING SQUARES. Locality. Date. Number of stages. Percent- age of parasit- ism. Waco, Tex Arlington, Tex. . . Victoria, Tex Dallas, Tex Arlington, Tex. . . Dallas, Tex Waco, Tex Navasota, Tex Natchez, Miss San Antonio, Tex Halletts\ille, Tex Dallas, Tex Arlington, Tex. . . Victoria, Tex Foster, La Talliilah, La Forbiug, La Shreveport, La. .. Hope, Ark Ada, Okla Fouke, Ark Waco, Tex Cuero, Tex Tallulah.La July July Aug. Aug. July July July Aug. Oct. July July Aug. Aug. July Sept, Dec. Aug Oct. Sept, Sept, July Sept, Aug. Sept. 23, 1909. ,1909.... 5, 1907.. 17, 1907. 17, 1908. ,1909.... 25, 1900. 17, 190S. 23,1908. 24, 1908. 1,1907.. 10, 1907. 6,1908.. 29, 190S. , 7, 1907.. 20, 1909. 29, 1907. 28, 1908. . 16, 1908 .4, 1908.. 27, 1908. . 20, 1900 31, 1903, ,,1909... 26 82 51 57 99 29 82 29 19 193 260 140 22 85 41 37 69 63 284 109 347 495 66.6 63.63 61.5 59.7 56.86 52. 63 52.6 51.75 51.3 48.27 47.3 47.15 46.92 45.71 45.47 44.7 43.9 37.84 33.33 31.74 26.05 23.8 21.3 15.35 IN FALLEN BOLLS. Victoria, Tex. . Ale.xandria, La Trinity, Tex... Corsicana, Tex. Victoria, Tex.. June 17-29, 1908 July 29, 1908... Aug. 24,1907... Sept. IS, 1906... Jan., 1909 14.4 9.09 8.3 5.9 5.74 IN HANGING BOLLS. Denison, Tex Calvert, Tex Goliad, Tex Do San Antonio, Tex. Victoria, Tex Natchez, Miss Marshall, Tex Trinity. Tex Waco, Tex Aug. 27, 1907. Aug. 23, 1907. July 28, 1908.. do July 24, 1908. Aug. 10, 1907. Jan., 1909.... Aug. 22, 1906. Aug. 9, 1906.. Sept. 20, 19011. 36.3 30.0 26.31 26.31 25.71 22. 7 1I4 13.5 12.0 11.8 These records give merely the highest percentages for each State in each year. There are many other records which might be included between the above iiiriires. Highest records of total insect control of the boll weevil. IN FALLEN SQUARES. Athens, Tex Hallettsville, Tex. Overton, Te.x Beeville, Tex Victoria, Tex Bee\'ille, Tex Cuero, Tex Goliad, Tex Vidalia, La Sherman, Tex Locality. Date. Aug. 1,1907.. Aug. 1,1908.. Aug. 1,1906.. do July 29, 1908.. Sept. 1, 1906.. June 20, 1908. Aug. 28, 1908. Sept. 15, 1908. July, 1909.... Percent- Number age of of stages. Insect control. 255 96.11 100 92.00 197 85.20 1,310 78.80 375 78.38 678 77.40 549 73.60 114 66.69 142 61.20 171 49.71 24 INSECT ENEMIES OF THE BOLL WEEVIL, nighest records of total insect control of the boll weevil — Continued. IN HANGING SQUARES. Locality. Date. Number of stages. Percent- age of insect control. Athens, Tex Arlington, Tex. Dallas, Tex Victoria, Tex. . . Waco, Tex Mansfield, La... Victoria, Tex. . . Aug. 1,1907.. July, 1909.... do July 29, 1908. July 1, 1906.. Sept. 1, 1906.. Aug. 1, 1907.. 75 55 57 87 99 244 253 84.00 75.44 69.99 58. 54 56.56 50.90 50.00 IN HANGING BOLLS. Mansfield, La. Waco, Tex... Overton, Tex. Mansfield, La. Sept. 29, 1906. Aug. 1, 1906.. do Sept. 24, 1906. 58.30 42.04 40.50 33.00 THE CORRECT BASIS FOR COMPARISON OP MORTALITY STATISTICS. As has been explained, the examinations have been made from various sources. It is therefore necessary to arrive at some true basis for the comparison of these data before an exact knowledge of the conditions existing can be obtained. The first mortality of the weevil is that due to proliferation. Dr. Hinds, in Bulletin 59 of this bureau, has shown that the average mortality of weevil stages in squares from proliferation is 13.5 per cent and that the average mortality in bolls is 6.3 per cent. In the absence of further data these two percentages are used as a basis for obtaining the weighted average mortality. As nearly as the proportion can be estimated throughout the entire season, 15 per cent of the weevil stages are to be found in bolls and 5 per cent in hanging forms. Wliether these arbitrary estimates be true or not, this is the only manner in which it will be possible to compare the mortality by the different factors in the various years. On this basis, therefore, a series of hypothetical tables has been erected. In order to show how the hypothetical average differs from the average obtained from the total examinations, two tables are given for each year, the first being a table giving the actual conditions in the four classes of infested material and the second table being a hypothetical table based upon 10,000 weevil stages on the arbitrary basis of 5 per cent of the stages in hanging forms and 15 per cent of the stages in bolls. The process continues by first subtracting the mortality by proliferation and then computing the mortality from climate, predators, and parasites from the remainder. The percent- ages of mortality given in the total line are based upon the total of 10,000 stages. SHARE OF INSECT CONTROL IN WEEVIL MORTALITY. 25 1906. — The data on the mortahty of the wee\al in 190G may tliere- fore be condensed and tabulated as follows: Table VII. — Boll-weevil mortality in 1906. Number of weevil stages. Percentage of stages alive. Percentage of stages killed by- Total per- centage of mortality. Class of forms. Climate. Predators. Parasites. Hanging bolls 5,452 4,n8 4,969 25.534 66.59 46.20 64.53 34.80 10.98 20.30 13.34 31.20 16.52 20.50 19.01 30.70 5.90 13.00 .90 3.30 33 41 53.80 Fallen bolls 35 47 65.20 Totals and averages 40,073 44.19 25.15 26. 31 4.31 55.81 Table VIII. — The hypothetical or iceighted average mortality of the boll weevil, 1906. o a .a 6 G to 1906— Mortality from— Prolifera- tion. Climate. Predators. Parasites. Total. Class of fonns. ^ ^_^ .-, ^ o o -d o -g -o . £ o 6C o 2 Q) Pr-S s 3 3 ?. • P 6 1 a s c3 a ? E a a a'i a C3 S c o a 3 m 3 S >- 3 Ph ^Z fe ^ « P-, IS P-i ;z; jc^ ^ :? Hanging bolls 0.75 75 6.30 4.7 70.3 10.98 7.7 16. ,52 11.6 5.90 4.1 37.4 28.1 Hanging squares 4.25 425 13. 50 57.4 367.6 20. 30 74.6 20.50 75. 4 13. 00 47.8 60.0 255.2 Total hanging.. 5.00 500' 62.1 437.9 82.3 87.0 51.9 283.3 Fallen bolls 14.25 1,425| 6.30 90.0 1,335.0 13 34 178.1 If* 01 253.8 .90 T^ 37.4 5.33.9 Fallen squares 80.75 8,075113.50 1,090.1 6,984.9 31.20 2,179.3 30.70 2,144.4 3.30 230.5 69.S'5,644.3 Total fallen 95.00 9,500! 1,180.1 8,319.9 2,357.4 2,398.2 242.5 6,178.2 Totals and aver- 1 1 1 ages 100. 00 10,000 12.42 1,242.1 24.39 2, 439. 7 24.85 2,485.2 2.94 294.4 04.61 6,461.5 1 Given 10,000 weevil stages. 1907. — The mortality during 1907 was 54.27 per cent when figured from the total number of stages and total mortality, thus showing a decrease of 1.54 per cent from the mortality of 1906 figured in the same manner. The parasitism sliowed an increase of 4.01 per cent. Table IX. — Boll-weevil mortality in 1901 Class of forms. Number of weevil stages. Percentage of stages alive. Percentage of stages killed by- Total per- centage of mortality. Climate. Predators. Parasites. Hanging bolls 431 2,612 342 10.020 76.80 51.40 49. 42 42.90 8.58 14.50 31.28 33.50 3.02 7.50 14.91 19.90 11.60 26.60 1.46 3.70 ''S 20 Hanging squares. . 48 60 Fallen bolls 50 58 57 10 Totals and averages 13,405 45.73 29.06 16.88 8.32 54.27 26 INSECT ENEMIES OF THE BOLL. WEEVIL. Following the plan adopted for the 1906 records these figures may be weighted for comparison with the earlier records. Table X. — The hypothetical or weighted average mortality of the loll ■weevil in 1907} 6 S n 3 eg ■w be O M bjO (S C 1 o a 1907— Mortality from - Prolifer- ation. .g B Climate. Predators. Parasites. Total. Class of forms. •6 Si 3 1 o u 2 si Pn ■6 a 3 ^5 o u ■6 3 s 3 o S'i 1 u E 3 ri % E 3 'A Hanging bolls Hanging squares 0. 75 75 4. 25 425 C.30 13.50 4.7 57.4 70.3 367.0 8.5S 14.50 6.0 53.3 3.02 7.50 2.1 27.7 11.60 26.60 8.1 97.8 29.70 55.50 20.9 236. 2 Total hanging . . 5. 00 500 02.1 437.9 59.3 29.8 105.9 257. 1 Fallen bolls Fallen squares 14. 25 80.75 1,425 8,075 6.30 13.50 90.0 1,090.1 1,335.0 31.28 0,984.9 33.50 417.6 2, 339. 6 14.91 19.90 199.0 1,389.8 1. 46 3.70 19.5 258. 4 50.90 62. 80 726.1 5,077.9 Total fallen 95.00 9,500 1,180.1 8, 319. 9 2.757.2 1,588.8 277.9 5,804.0 Totals and aver- ages 1 100.00 10,000 i 12.42 1.242.1 28. IG 2,816.5 10.18 1,618.6 3.83 383. 8 GO. 61 6,001.1 1 Given 10,000 weevil stages. This table shows a weighted increase of 0.89 per cent for parasites and a weighted decrease of 4 per cent for all agencies due to the falling off in control by predators. 1908. — The mortality during i90S was 44.84 per cent when figured from the total number of stages, the total mortality thus shomng a decrease of 9.93 per cent from 1907. The parasitism showed an increase of 1.68 per cent. Table XL — Boll-weevil mortallhi'in 11/08. Number of weevil stages. Percentage of stages alive. Percentage of stages killed by- Class of forms. Climate. Predators. Parasites. All agen- cies. 1,8.39 5,922 941 20,844 49.40 49. 01 70. 25 57.28 38.48 19.24 20. 08 20.30 3.97 9.80 5.95 15.18 8.15 21.70 3.71 7.15 50.60 Hanging squares 50.99 Fallen bolls 29.75 42.72 Totals and averages 29, 546 55. G6 21.21 13.12 10.00 44.34 SHARE OF INSECT CONTROL IN WEEVIL MORTALITY. 27 Following the plan adopted for the 1906 and 1907 records these figures may be weighted for comparison with the earlier records. Table XII. — The hypothetical or veighted average viortahty of the boll weevil in 1908.^ 6 R 1908— Mortalily from — Prolifer- ation. Climale. Predators. Parasilos. Total. Class of fonns. F? ac ^ <-H <- ,^ *« o ■73 o -a o T3 o M l_* Q^ j_j ^ 0) ° «- O 4J 60 b«_' M M So-o M §£-• M a E 3 a o 1 .g B at a 2 E s a il 0) fc. a a g ii s 3 S2 C O 2 a 3 Pi 2; Ph z A Ph 2; p^ 1 Ph 12; Ph Z Hanging bolls 0.75 75 6.30 4.7 70.3 38.48 27.1 3.97 1.4 8.15 .5.7 .51.80 38. 9 Hanging squares 4.25 425,13.50 57.4 307.6 19.24 70.7 9.80 30.0 21.70 79.8 57.30 243.9 Total hangiag.. 5.00 500 62. 1 437.9 97.8 37.4 85.5 282.8 Fallen bolls 14.25 1,425 6.30 90.0 1,335.0 20.08 268. 1 5. 95| 79. 4 ,3.71 49.5 .34. 10 487.0 Fallen squares 80.75 8,075 13.50 1,090.1 0,984.9 20.301,417.9 15. IS'I.OOO. 3 7.15 499. 4 50.30 4,007.7 Total fallen 95.00 9,500 I.ISO. 1 8,319.9 |1, 686.0 1,139.71 548.9 4,554.7 Totals and aver- i 1 1 1 1 ages 100.00 10,00012.42 i 1,242.2 17. 83 1, 783. 8 11. 77jl, 177. ij 6. 34 634. 4 48.37 4,837.5 1 Given 10,000 weevil stages. This table shows a weighted increase of 2.51 per cent for parasites and a weighted decrease of 12.24 per cent for all agencies, due to the falling off in control by both climate and predators. 1909. — The mortality during 1909 was 41.73 per cent wlien figured from the total number of stages, the total mortality thus showing a decrease of 2.61 per cent from 190S. Tlie parasitism showed also a decrease amounting to 4.6S per cent. Table XIII. — Boll-weevil viortality in I'jO'.i. Number of weevil stages. Percentage of stages alive. Percentage of stages killed b y— Class of forms. Climate. Predators. Parasites. All agen- cies. Hanging bolls 1,534 1,959 573 7,587 53.33 61.16 54.82 58.79 37.94 12. 96 27.74 26. 58 5.21 6.38 1.5.00 12. 39 3. .52 19.49 2.44 2.24 Hanging squares 38.84 Fallen bolls Fallen squares 41.21 Totals and averages 11,653 58. 27 25. S4 10. 56 5.32 41.73 28 INSECT ENEMIES OF THE BOLL WEEVIL. Following the plan adopted for the three preceding years these figures may be weighted for comparison with the earlier records: Tablk XIV. — Tlie hypothetical or weighted average mortality of the boll weevil in IbO'j.^ u a a ft O M f2 PREDA- TORS PREt)ATOPS 0/<^ARVAE HyPERPARAS/TE THESE /NUMEROUS E/\/EM/ES ALSl AREmOWA/ TO ATTACK AT LEAST. E2 OTHER WEEI//LS 3/ OTHER SPEC/ES OF PLANTS e HyPER- PARAS/TES Fui. G.— Diagram illustrating the boll- weevil complex. (Original.) triculosus. Mr. Banks has stated that it may possibly be different from the European species, but as it is known throughout tliis country imder the above name it is so quoted here. IMr. Rangel PARASITES OF WEEVIL AND OTHER HOSTS. 45 WEOTMER HOSTS ^R/A B/S/e/VAT/i Lar/a COMPRESS/CORAJ/S IaRIA eXfGUA Lar/a obtecta Laria 0CHRAC£A Lar/a sallae/ \ SpERMOPMAGUS ROB/NMe BRACHyrARSC/S alternatus Araecerus pasciculatus l/xus musculus L/xus scPoa/coLus Smicronvx tvcho/des Desmor/s scapaus Ap/on decolopatum Ap/om grjseum Ap/om n/grum Ap/oa/ rostrum Ap/oa/ segwpes AIacrorhoptus sphaeralc/ae Tachypterellus quadric/bbos Smicraulax tuberculatus Afi/THOfJOMUS AEA/EOLUS Anthoa/omus albopilosus Anthoa/omus aphanosteph/ Anthoa/omus eugeaji/ Aa/thomoa^us pulvus Aa/thoa/oa/ius grand/s Aa/thoajoa^us heterothecae Aa/thoajomus ligatus Anthonomus nebulosus Anthonomus u/grinus Anthonoa^us s/gajatus Aa/THCNOA/!US squaa^osus TyCHIUS SORD/puS CONOTRACHELUS AFFJAJ/5 CONOTRACHEWS ELEGANS CONOTRACHELUS JUGLANDIS CONOTRACHELUS fl/ASO conotrachelus a/ea/uphar Chalcodera^us aea/eus TyLODERMA POVGJLATUAa Gerstaecker/a a/obius auleutes tenu/pes Crapoaz/us /NAEQUAUS Ceutorhyajchus SP. Rhinoajcus PYRRROPUS Baris cuajeipeajaj/s BaRIS SP. Orthoris CRorcR/f Tr/crobar/s COMPACTA Trichobaris TEXAAJA Trichobaris trinotata Aa/ipeloglypter sesostris ZygodaR/s xantroxyu 6alan/a/us a/as/cus Calandra oryza TOTAL A/OAJe£Tf OT HOSTS (4: S J m ^ 5 3 p < ^ Oj 0) (0 ^ 5i ^ # i K 5; CT 52 q: § III 1 ■ rx / X X 2 X X X X ^ X / 2 X y X X X X 4- X X 2 > f X X 2 X X 2 X X X 3 X / X / X / X / X / X / > / X / X X 2 X X X X 4 X / X V X X 4 X / > X X 3 X X 2 X y > X X X X X X X X X X X X X X X X X y X X X X as X X 2 >< / y / X / X X 2 X X X 3 X / X X 2 X X 2 X X 2 X / X X 2 y / X X X X 4 X / X / X / ' X / X / X / X X 2 X / X x - X 3 X X X X 4 X X 2 X / •)^ X 2 X / X / 2 £ £ n / / Z ^ 3, / /e L / s /& 2 13 /f 3 L 10 / / / 12, Fig. 7.— Diagram giving the parasites of the boll weevil and their other hosts. (Original.) 46 INSECT ENEMIES OF THE BOLL, WEEVIL. pointed out that these mites reproduce viviparously and that their offspimg are mature and fertile at birth. He found that when they attach themselves to a host the abdomen commences to inflate until it becomes many times larger than the thorax. The time requii'ed for engorgement varies from 2 to 5 days. "VVlien the abdo- men commences to grow, the young commence to leave the parent. The males fertilize the females before leaving the parent's body and shortly afterwards die. An average of 100 female offspring to an individual was recorded. Rangel found that in 48 hours, 21 stages out of 40 in squares were attacked by the mites. In larger series of tests, after four days 50 out of 153 weevil stages in squares were attacked, or 32.6 per cent. a Fig. 8. — Pediculoidcs ventricosus: a, Adult female before inflation of abdomen with eggs and young; 6, adult female after inflation of abdomen with eggs and young. Greatly enlarged. (Redrawn from Brucker.) Pediculoides n. sp. This mite was discovered in the laboratory at Dallas, Tex., June 13, 1907, by the senior author. Careful observa- tions on the length of generations were made with the following results: A gravid female was isolated June 13 and on June 17 there were 31 gravid mites. All but 5 were removed. On June 19 there were many offspring, one mite being well grown. On June 21 the fourth generation began to appear. In other words, between June 13 and June 21, that is, in less than 8 days, there were two com- plete generations. Another genealogy was as follows : Parent isolated June 13, second generation began to appear June 14, were mature FLIES WHICH PARASITIZE THE WEEVIL. 47 June 17, and reproducing June 19. On June 24 the third generation was reproducing. In this case there were 11 days covering two com- plete generations. The mites appeared wilhng to feed on any insect food available, as they were first found feeding on stages of Trichoharis compacta, then on boll-weevil stages, and finally on a Baris, on boll-weevil parasites isolated in rearing tubes, and on Hydnocera pubescens. They were reared readily on larvse of CMorion cyaneum and Polistes ruhiginosus. ]\ir. John B. Railsback, of Forbing, La., found that they attacked the larvae of the bollwonn and other smooth cater- pillars very readily. TYROGLYPHID.E. Tyroglyphus hreviceps Banks was described as a weevil enemy from Victoria, Tex. This, or a similar mite, was found to be very- abundant at Calvert, Tex., in 1906. 4. FLIES WHICH PARASITIZE THE BOLL WEEVIL. Veiy few Diptera are laiown to be primarily parasitic upon boll weevils, but the genera Myiophasia and Ennyomma in the Tacliinidse seem to be confined to hosts of this nature. The genus Aphiochseta, of the Phoridse, contams at least 3 species which have been reared under circumstances pointing to primaiy parasitism. The larvae of the tachinids work singly and those of Apliiochseta several to a host, but in both cases as endoparasites. Wlaen the former become full grown they completely fill the sldns of the weevil larva3 and fre- quently the appendages of Myiophasia penetrate to the exterior. The weevil skin partakes of the character of parchment and becomes a cocoon witliin wliich the fly larva pupates and fi'om wliich the adult emerges. On the contrary the Apliiochseta larvae leave the host when they have reduced it to a shell and pupate in the weevil cell. The flies evidently prefer to attack weevil stages in moist, shaded spots in preference to sunny locations. By tliis habit they become very valuable in fields located in bottom lands where the diy condi- tions conducive to parasites like the hymenopterous parasites are absent. The puparia of Myiophasia and Ennyomma are so near like that of the chalcidoid internal parasite Tetrastichus hunteri that they can be differentiated only by the larger size of the dipterous puparia. PHORID.E. ApMochseta nigriceps Loew (determined by D. W. Coquillett) . Apliiochseta fasciata Fallen (determined by D. W. Coquillett). ApMochseta pygmsea Zetterstedt (determined by D. W. Coquillett) . 48 INSECT ENEMIES OP THE BOLL WEEVIL. On September 12, 1906, in dry hanging bolls collected at Dallas, Tex., a weevil larva was found parasitized and isolated in a separate tube, with the following record: "Veiy small parasite larva on small weevil larva." On September 26 a single specimen of Apliiochsnta nigriccps Loew was reared and the following note made by the senior author: '* Found dipterous puparium, skin of liaiiy para- site larva (may be the dipteron or a hymenoptcron) ; also remains of weevil larva." On October 6, 1906, in hanging bolls collected at Dallas a weevil larva was isolated with the note, "Weevil larva full of dipterous larvae." Eleven larvte left this host larva and pupated. On October 29, 7 Aphiocliseta {Vj fasciata Fallen and two A. pygmsea Zetterstedt were reared. At least the latter case seems to be very strong evidence of primary parasitism. These flies are reared frequently from bolls and many are perhaps scavengers. Two other species, A. epeirse Brues and A. scalaris Loew, have also been reared from cotton forms at Calvert, Tex. Kecords made in 1911, at Tal- iulah, La., by Mr. Harry Pinkus, point conclusively to primary parasitism. TACHINID^. Myiophasia senea Wiedemann is recorded from a number of very important weevils. Of these, Balaninus nasicus Say (the acorn weevil), Conotrachelus juglmidis LeConte(the walnut weevil), ^/n;pe- loglypter sesostris LeConte (the grapevine gall-maker), Conotrachelus affinis Boheman (the hickory-nut weevil), and Conotrachelus elegans Say (the pecan-gall weevil) are all weevils which enter the ground for pupation, carrying their parasites with them, and consequently it becomes necessary for the flies to emerge from the weevil cell through several inches of earth before attaining freedom. The only weevils which this fly attacks and which do not enter the ground for pupation are the boll weevil and Triclioharis compacta Casey (the Jamestown- weed pod weevil). Very few records have been made to ascertain its developmental period, but the three records at hand indicate from 22 to 29 days as the period from collection of the infested material to the maturity of the fly. This period would cover largely the under- ground period only. Ennyomma (Loewia) glohosa Townsend. Several specimens of this fly were reared during 1907 by Mr. C. R. Jones at Alexandria, La., as primary parasites of the boll weevil. It is a very common parasite of Chalcodermus seneus Boheman (the cowpea-pod weevil) in the Southern States. 5. THE HYMENOPTEROUS PARASITES OF THE BOLL WEEVIL. So much information has been gained concerning the hymenopter- ous parasites of the boll weevil that it will be necessary to omit manj^ of the technical facts learned about them. The present sec- HYMENOPTEEOUS PARASITES OF THE WEEVIL. 49 tion is concerned with the sources of the parasites and with important records of their occurrence, whUe the other interesting facts to be presented are inchided in the five following sections : CHALCIDOIDEA. CHALCIDID.E. CHALCIDIN^. SMICRINI. Spilochalcis sp. A single male of this species was found dead in a weevil ceil with the remains of the weevil and its own exuvium in a hanging square collected August 10, 1907, at Victoria, Tex. TORYMID.E. MONODONTOMERIN.E. Microdontomerus anthonomi Crawford (fig. 9). Brachytarsus alter- natus Say was formerly the only weevil recorded as a host of this species. A male and female of this parasite were reared on Septem- 'EiG.'i.— Microdontomerus anthonomi: Adult. Much enlarged. (Origiual.) ber 12, 1907, from pods of the flowering shrub Amorpha fruticosa, at Dallas, Tex., which were highly infested by (Bruchus) Laria exigua Horn. In 1906, in which year this parasite was first discovered, it ranked as seventh species in importance as a boll-weevil enemy. In 1907 it advanced to fourth place and was very important in the central black-prairie region of Texas. In 1909 the easternmost limit of our records was Tallulah, La., which did not become infested by the boll weevil until 1908. EURYTOMID.'E. EURYTOMINI. Euryfoma tylodermatis Ashmead {BruchopTiagus Tierrerse Ashmead). This is without doubt one of the most important species under consideration, having a range of distribution practically coexten- 16844°— Bull. 100—12 4 50 INSECT ENEMIES OF THE BOLL WEEVIL. sive with that of its host, the boll weevil. In previous publi- cations it has been recorded as a parasite of Lixus musculus Say, L. scrohicollis Boheman, Apion segnipes Say, Anthonomus JieterothecsR Pierce, Anthonomus squamosus LeConte, Tyloderma foveolatum Say, and Orthoris crotchii LeConte. To this list may be added (Bruchus) Laria exigua Horn in Amorpha pods at Dallas, Tex.; (Bruchus) Laria sallxi Sharp in pods of huisache ( VaclieMa farnesiana) col- lected at Victoria, Tex.; Spermopliagus rohinise Schonherr in pods of the honey and water locusts ( Gleditsia triacanthos and G. aquatica) in Louisiana; Macrorhoptus sphxralcise. Pierce in pods of Sphseralcia at Del Rio, Tex.; Smicraulax tuherculatus Pierce in mistletoe stems at Dallas, Tex.; TricJwharis texana LeConte in stems of Solanum rostratum at Cisco and Victoria, Tex.; and also Triclioharis trinotata Say; and finally it was reared in September, 1908, from Baris sp. in roots of ambrosia at Camden, Ark., by C. E. Hood. Euryfoma sp. A female primary parasite and a male accidentally secondary on Microhracon mellitor Say were reared from hanging squares collected August 10, 1907, at Victoria, Tex. PERILAMPID.E. Perilampus sp. A single individual was reared from the boll weevil iji an isolated weevil cell by C. E. Hood from squares collected Sep- tember 7, 1907, at Shreveport, La. Another specimen of Perilampus was reared from squares collected at Granbury, Tex., August 8, 1907, but its source could not be proved. If it were not for the definite record made by Mr. Hood these species could hardly be placed in this list. This record may possibly be based upon the parasite of an intruder in the weevil cell instead of upon the weevil itself. It is not impossible that after several years this parasite may be found normally as a boll-weevil parasite, as was the case with Sigalphus curculionis. ENCYRTID^. EUPELMIN^. Cerambycohius cyaniceps Ashmead. The list of hosts of this spe- cies as previously recorded included Anthonomus alhopilosus Dietz, {Bruchus) Laria ohtecta Say, L. exigua Horn, Lixus musculus Say, Tricholaris texana LeConte, and Tyloderma foveolatum Say. To this list may be added Laria hisignata Horn in pods of Acuan illinoensis; L. ochracea Schaeffer in pods of Vicia sp.; L. sallxi Sharp in pods of huisache ( Vachellia farnesiana) ; Spermophagus rohinise Schonherr in pods of Gleditsia triacanthos at Alexandria, La.; Lixus scrohicollis Boheman in stems of Ambrosia trifida and A. psilostaclmja; Apion rostrum Say in pods of Baptisia tinctoria at Washington, D. C; Tachypterellus quadrigibhus Say in fruit of Cratsegus mollis at Vic- toria, Tex.; Smicraulax tuherculatus Pierce in stems of mistletoe HYMENOPTEEOUS PARASITES OF THE WEEVIL. 51 (PJioradendron flavescens) ; Tychius sordidus LeConte in Baptisia pods at College Station, Tex.; Trichoharis compada Casey in pods of Datura stramonium at Paris, Tex.; and, furthermore, on Langurla sp. in stems of Gaura sp. at Ballinger, Tex. Ceramhjcohius cushmani Crawford. This parasite was reared in small numbers as early as 1906 in southern Texas from the boll weevil. It has been reared from Laria ochracea Schaeffer in pods of Vicia sp.; from L. sallsei Sharp in pods of VaclieUiafarnesiana; from Arsecerus fasciculaius DeGeer in fruit of chinaberries ( Melia azeda- racli) at Victoria, Tex.; and from Trichoharis texana in stems of Solarium, rostratum . Oeramhycohius sp. On February 23, 1909, a male of a green species of Cerambycobius was reared from the weevil in squares collected at Natchez, Miss., January 19. PTEROMALID.E. PTEROMALIN^. Catolaccus hunteri Crawford. This is the species which in all pre- vious articles on the boll weevil has been known as Catolaccus incertus. Its hosts as now known are Laria compressicornis Schaeffer in pods of Acuan illinoensis; Tachy pterellus quadrigihhus Say in fruit of Cratsegus spp. ; Smicraulax tuherculatus Pierce in stems of Plioradendron flaves- cens; Anthonomus seneolus Dietz in buds of Solanum spp. ; Anthono- mus alhopilosus Dietz in seeds of Croton sp.; Anthonomus eugenii Cano in fruit of pepper {Capsicum spp.); Anthonomus heterothecx Pierce in heads of Heterotheca ' subaxillaris; Anthonomus nebulosus LeConte in buds of Cratxgus spp.; Anthonomus signatus Say in buds of dewberry (Ruhus spp.) ; Anthonomus squamosus Le Conte in heads of Grindelia squarrosa nuda; {Acalles) GerstsecTceria nohilis Le Conte in joints of Opuntia spp. ; Zygoharis xanthoxyli Pierce in berries of Xan- thoxylum clava-herculis. Catolaccus incertus Ashmead. This parasite is also very common and is known from a considerable number of hosts, among which are Laria exigua Le Conte in pods of Amorpha fruticosa; Apion decolora- tum Smith in pods of Meihomia paniculata; Apion griseum Smith in pods of Phaseolus spp. ; Apion nigrum Smith in buds of Rohinia pseu- dacacia; Anthonomus alhopilosus Dietz in seeds of Croton spp. ; Antho- nomus aphanostephi Pierce in heads of Aphanostephus sMrrohasis ; Anthojiomus fulvus Le Conte in buds of Callirrhoe involucrata; Antho- nomus nigrinus Boheman in buds of Solanum carolinense; Anthonomus signatus Say in buds of strawberry (Fragaria virginiana); Auleutes tenuipes Dietz in buds of Galpinsia hartwegi; Ceutorhynclmis n. sp. in crown of Selenia aurea; Baris cuneipennis Casey in roots of Helenium tenuifolium and Calandra oryza Linnaeus in corii 52 INSECT ENEMIES OF THE BOLL WEEVIL. Hahrocijfus lyiercei Crawford, This is a brilliant green parasite resembling Catolaccus antJionomi Ashmead. It is reared from the boll weevil mamly in the fall and from hibernated inuividuals in the spring. It has been reared from Laria compressicornis Schaeffer in pods of Acuan illinoensis. (See fig. 10.) Lariophagus texanus Crawford. There is every evidence that this species is a true parasite of the boll weevil, although it has not been positively reared by isolation from the boll weevil. On August 17 and 27, 1907, two specimens were reared from material collected at Hallettsville, Tex., August 13; on August 19 and 23 three specimens were reared from cotton squares collected at Victoria, Tex. ; on August 29 three specimens were reared from squares which were collected at Eagle Lake, Tex., on August 14. The Victoria lot was pecuUar in that it furnished the first records of Cermribycohius cushmani Crawford, Spilochalcis sp., and Eurytoma n. sp. This species is described as a parasite of (Bruchus) Laria prosopis Le Conte. It undoubtedly also attacks L. sallsei Sharp, which also breeds in the pods of huisache; furthermore, the species was reared from stem galls of Leucosyris spinosus containing Anthonomus ligatus Dietz. Tetrasticlms hunteri Crawford. This interesting new parasite of the boll weevil was first reared in the fall of 1908 from isolated parasitized individuals of the boll weevil collected at Natchez, Miss., by H. S. Smith. It is internal in weevil larvae and pupae and has even been reared from immature adults. A parasitized individual can easily be told by its brownish color and smoothening of the vari- ous segmental wrinkles. In more advanced stages of the parasite's development, the parasitized in- dividual becomes a mere bro"\vn skin of parchment. Tliis skin serves as puparium for the parasite. The developmental period is of con- siderable length in the fall. Specimens isolated in November do not mature until April or May. In 1908 it was found only at Natchez, IVIiss., and Monroe, La., but in 1909 it was reared at a number of places in Louisiana and also at Arlington, Tex. This species gives an ex- cellent example of the adjustment of native parasites to the boll weevil. ICHNEUMONOIDEA. ICHNEUMONID.E. PIMPLIN.i;. Fig. IQ.—Habrocytus piercei: Pupa. Much enlarged. (Original.) Pimpla sp. On January 27, 1909, a larva of this species was isolated from a weevil larva in squares collected at Nacogdoches, Tex. This became a mature female on February 23. HYMENOPTEEOUS PARASITES OP THE WEE\^I. 53 BRACONID^. SIGALPHIN^. Sigalplius curculionis Fitch. Previous to the summer of 1908 the first record of rearing this species (see fig. 11) from the boll weevil was considered doubtful, but beginning in August it was reared repeatedly in material from Ruston and Monroe, La., and Natchez, Miss. Its other hosts are Conotrachelus afjinls Boheman in hickory nuts; Cono- trachelus elegans Boheman in petioles of hickory at Dallas, Tex., and in galls of Phylloxera devasfatrix on pecan {Hicorla pecan) at Dallas and Victoria, Tex. ; Conotraclielus juglandis Le Conte in walnuts (Jug- lans nigra); Conotraclielus nenuphar Herbst in fruit of plum, peach, etc.; Tyloderma foveolatum Say in stems of Onagra biennis at Wash- ington, D.C. ; Trichoharis texana Le Conte in stems of Solanum rostra- turn; Trichoharis trinotata Say in stems of potato (Sol- anum, tuherosu'in) ; and Zygo- haris xantJioxyli Pierce in seed of Xanthoxylum clava- herculis. Urosigalphus anthonomi Crawford has never been reared since the original records which were made at Brownsville, Tex. Urosigalphus schwarzi Crawford. This Guatemalan boll weevil parasite has never been reared in the United States. Urosigalphus n. sp. At Arlington, Tex., in 1909, a single specimen was reared from an isolated cocoon. Fig. 11. — Sigalphus curculionis: a, Male; h, female; c, an- tenna. All enlarged. (After Riley.) BEACONING. Microhracon mellitor Say.^ This parasite (see fig. 12) still holds the lead as the most important boll-weevil parasite. Its other host relations are only partially discovered. The following hosts have been ascertained: Desmoris scapalis Le Conte in heads of Siderantlius ruhiginosus; Smicraulax tuberculatus Pierce in stems of Phoradendron Jiavescens; Anthonomus alhopilosus Dietz in seed of Croton spp.; Anthonomus eugenii Cano in fruit of pepper 1 Bracon mellitor Say is recorded by Giranlt (1907) as a parasite of the lesser peach borer {Synanthedon pic- tipes Oroto and Robinson) and of tiie peach borer (Sanninoidea exUiosa Say). The gregarious habit of these parasites appears to prove that the determination was incorrect. Mr. F. E. Brooks, of West Virginia, has fur- nished the record of this species from Sanninoidea exitiosa and also from Craponius inxqualis Say at French Creek, W. Va. The determinations were made in the Bureau of Entomology. Dr. F. H. Chittenden states that he reared this species from the strawberry leaf-roller, A ncylis comptana Froelich (fragarix Walsh and Riley), at Cabin John, Md., July 9, 1899. It is probable that all parasites of Lepidoptcra determined as Bracon mellitor belong to some other species. The lepi-dopterous and coleopterous parasites are not dis- tinguishable by structural characters, but are so different in habits that it is considered advisable to call the lepidopterous parasite Microbracon dorttator Say aud the coleopterous parasite M. mellitor Say. 54 INSECT ENEMIES OF THE BOLL WEEVIL. (Capsicum sYip.); Anthonomus fulvus Le Conte in buds of CalUrrhoe involucrato; Antlionomus squamosus Le Conte in heads of GriTuLelia squarrosa nuda; Conotrachelus nenwphar Herbst in peaches ; Tyloderma foveolafum Say in stems of Onmjra hiennis; Cra/ponius inxqualis Say in fruit of grape ( Vitis spp.), and Barls sp. in roots of Ambrosia sp. 0. BIOLOGICAL NOTES UPON THE PARASITES OF THE WEEVIL. A number of very interesting facts, wliich deserve mention in an economic bulletin, have been learned about the biology of the parasites. ABUNDANCE OF PARASITES. It is unusual for the parasites of the boll weevil to be found flying in numbers. Their work is in a general way quietly and unostenta- tiously done, but occasionally it is the pri\dlege of the observers to see swarms of parasites hovering around the food plant of their favorite host. At Clar- endon, Tex., in August and September, 1905, Mr. C. R. Jones and the sen- ior author witnessed large numbers of Microhracon nuperus and Tetrasticlius sp. hovering around the highly infested pods of Mentzelia nuda. The par- asitism in pods gathered at this time was so high that much superparasit- ism by Tetrasticlius upon theMicrobracon occurred. At Ruston, La., in Octo- ber, 1907, the senior author saw Catolaccus hunteri flying in all directions and resting on the flowers and leaves of Heterotlieca suhaxillaris and found a very high parasitism of Anthonomus heterothecse. by this species. In November, 1908, in this same field at Huston, a very high percentage of parasitism of the boll weevil by Catolaccus was found. In September, 1908, Mr. Hood saw many species of parasites around the flower heads of Vernonia at Camden, Ai-k. During the same month Mr. H. S. Smith found Catolaccus hunteri swarming on Croton capitatus contain- ing Anthonomus albopilosus. Such observations are very important because they suggest excellent sources for parasites to be used in introduction experiments or suggest forcing of the parasites to the boll weevil by the elimination of the host. Fig. 12.- ■ Microbracon mellitor: Adalt. Mucheolarged. (From HiintPi-and Hinds.) BIOLOGICAL NOTES ON THE PARASITES. 55 FREQUENTATION OF NECTARIES. The feeding habits of adult hymenopterous parasites have long escaped observation, but witliin recent years the intensive study of parasites has proved that very little can be accomplished in the prop- agation of parasites unless they can be fed. In the case of the para- sites of the boll weevil it is impossible for the adults to obtain nour- ishment from the host in which they are ovipositing, as has been proven in the case of parasites of externally feeding insects. The host plant of the boll weevil, however, furnishes the desired food. The nectaries of cotton are about as plentiful as those of any other plant. The majority of varieties of cotton have three large nectaries on the leaves and also have them on the outside and inside of the involucre, as well as on the inside of the flower. Frequent observa- tions of cotton plants wliich were producing considerable nectar have enabled us to observe practically all of the parasites of the boll weevil, as well as all of the ant enemies and many other insects. Some of these insects wliich visit the nectaries are injurious to the cotton plant, but the majority seem to be beneficial. The quantity of nectar secreted by various varieties of cotton is quite variable. The variety which seems to secrete more than any other which has been observed is the Egyptian Alit Afifi. Tliis variety is frequently surrounded by large numbers of beneficial hymenop- terous insects, although at the same time it appears to be very sus- ceptible to boll weevil attack. HELIOTROPISM. The majority of the hymenopterous insects wliich have been under observation in tliis investigation appear to be positively heliotropic. In general this tendency can be utilized in rearing-cage technique to induce the parasites to go into small tubes placed in the rearing boxes, from which they can be easily removed. It has been noticed in rearing cages in wliich there were growdng plants with plenty of food, air, and heat, that the parasites sought the lightest portion of the cage rather than the plants wliich could give them some shade from the hot sun. The activity of the parasites is greatest when the sunlight is most intense. Observations at the nectaries of the Eg3^ptian cotton con- firmed this. Wlien the sun was shining the parasites were very active at the nectaries and flying around the plants, but when a cloud passed over they seemed to disappear entirely. On cloudy days none of the Hymenoptera, except the most industrious bees and wasps, was to be found at the nectar. Trelease (1879) states that "the extrafloral nectar of the cotton plant is far more abundant during night and in the early morning than at any other time, and 56 INSECT ENEMIES OF THE BOLL WEEVIL. this is true whether we consider the invokicral or fohar glands," The parasites probably frequent the nectaries during the morning sunlight hours and then are equipped to go about their other duties during the hottest part of the day. In addition to these actual observations as to the preference of parasites there are other very strong proofs of heliotropism. It has been found that there is a decided increase in the parasitism of weevil stages in hanging forms exposed to the sun over those in fallen forms which are more or less shaded. It is also apparent that the fallen forms most exposed to the sun receive the greater amount of para- sitism. Among the hymenopterous parasites there is only one at present which seems to prefer a moist shady place for its work. This is Tetrastichus liunteri C^rawford, which is an internal parasite. A numerical study of the records of rearing of parasites from the boll weevil shows that in the majority of the species the males are relatively fewer than the females. The following table will show the percentage of each sex and also the number of parasites upon which these percentages are based. Table XIX. — Relative percentages of the sexes of boll-iveevil parasites. Species. Total in- dividuals. Percentage of sexes. Female. Male Microbracon meUitor Catolaccus liunteri Catolaccus incertus Habrocytus piereei Cerambycobius cushmani Cerambycobius cyaniceps Cerambycobius sp Ennyomma globosa Etirytoma tyloderniatis Eur'ytoma sp Lariophagus texanus Microdontornerus antUonomi Myiophasia xnea Sigalphus curculionis Tetrastichus liunteri 429 30 64 509 1 8 433 2 2 223 2 13 41 Per cent. GO. 78 78.37 81.12 100.00 71.88 70.34 37.50 64.90 50.00 50.00 84.76 50.00 61. 54 100.00 Per cent. 39.22 21.63 18.88 28.12 29.66 100.00 62.50 35.10 50.00 50.00 1.5.24 50.00 38.46 OVIPOSITION. It has been found by numerical study of the large number of para- sites collected during the last five years that whenever the parasitism in a field reaches between 50 and 70 per cent there is a strong likeli- hood of reduplication, with resulting superparasitism. The exact records of superparasitism obtained in this investigation have been published in another article (Pierce, 1910). Parasites have no power of discerning the presence of another egg on the prospective hosts, and hence there occurs at times a tremendous duplication of energies. Bui. 100, Buieau of Entomo'ogy, U, S. Dept. of Agriculture Plate II. Eggs of Boll-Weevil Parasites. Fig. 1.— Type II. Micnidontom, rm anthononii; Calvert. Tex., Augu.Mt 23, 1907; color white; size 0.38 by 11 mm. Fig. 2.— Type VI. Unidentified egg: Dallas, Te.x., November 11, 1907. color white; size 0..S5 by 0.19 mm. Fig. 3.— Type I. Crraiiibi/rdbim ei/nniccps; Sa, view from side: Sh. view from end: color white: size about O.S mm. ' Fig. 4.— Tvpe III. Eiiri/- Idiiiati/todentiatis: Dallas, Tex.. August 22, 1907: color gray; size O.tlS bv 0.21 mm.; !,a, side view of another egg. Fig. 5.— Type IV. CutolaccuK hiinteri; Dallas, Tex,, August 22, 1907; cctlor white: size 0.(i2 by 0,22 mm. Fig. 6.— Type V, Unidentified egg; Glenmora, La., August 2;i. 1907; color grav: size 0.44 bv 0.11 mm. (Original. ) Bui. 100, Bureau of Entomoiogy, U, S. Dept. of Agriculture, Plate III, Parasites of Weevils. Fig. \.—E>iriitoma tuloflrrmatix. pui.ii. Via. ■l. — Catolfunis incaiuf, pupca. _Fig_. S.—Crram- bvcnbiiis rii,u!irrij:<. pupa. Fig. i.—Micn>il<„itown;i>f arithonomi. pupa. Fig. o.-Larya ol microbracon. Fig. e.-MtcmbramnweUUor.vupsi. Fig. 7.-Larvaotchalcidoid. Mucli enlarged. (From Pierce.) DEVELOPMENT OF THE PARASITES. 57 It may therefore be possible that a parasite will visit the same square several times and oviposit. In general it may be said that as the primary parasitism of the boll weevil increases the superparasitism also increases, with the result that sometimes the parasitism might be considerably increased if every egg reached a single host. The following instances will illustrate this. At Calvert, Tex., 41 stages were attacked by 44 parasites, although only 3G.5 per cent of the weevils were parasitized. If every parasite egg had reached a host, there would have been 107.3 per cent parasitism. At Dallas, Tex., out of 309 weevil stages, 44.6 per cent were attacked by 216 parasites. The possible parasitism was 69.9 per cent. Many other instances of this kind could be given, but these two cases illustrate the condition perfectly as it exists in many places during the fall of each year. The time for oviposition apparently differs for the various species. Microhracon mellitor, as a rule, oviposits before the boll-weevil larva has constructed a cell, that is, several days before the flared square falls or dries. Eurytoma tylodermatis appears to oviposit in squares on the plant after the normal time of falling and hence is more important in hanging dry sc^uares. Catolaccus spp. and Microdontomerus antlio- nomi favor fallen forms for oviposition. The chalcids generally oviposit after the weevil larva has formed its cell. Tetrastichus hunteri is most frequently found in fallen squares. 7. THE DEVELOPMENT OF THE PARASITES, THE EGGS. The eggs of the boll-weevil parasites are all oblong-elliptic and either smooth or sculptured. The eggs of several species have at one or both ends a small tube which is tied into a knot. SLx tyiws of eggs of the boll-weevil parasites have been closely observed and designated by number in the records of rearing. These are illus- trated on Plate II. The eggs of all the boll-weevil parasites are placed in the weevil cell or on the larva or pupa and usually wdthout injuring the latter. Type I. — Type I is the egg of Ceramhycohius cyaniceps. It was determined for the species by the use of a mica plant cage in which the parasite was isolated with newly infested squares. This egg is about 0.8 mm. long, pure white, cylindrical, unsculptured, and with a narrow neck, which is twisted into a knot, probably by the ovi- positor after the latter has released it. (Plate II, fig. 3.) Type II. — This is the egg of Microdontomerus anthonomi, as shown by the rearing of an isolated specimen. The color is white, the egg being distinguished by the slightly papillose sculpture and by the nipple at one end. It measures 0.38 mm. in length and 0.11 mm. in breadth. (Plate II, fig. 1.) 58 INSECT ENEMIES OP THE BOLL WEEVIL. Type in. — This is the egg of Eurytoma tylodermatis , found by the isoLation of a larva seen in the act of hatching, coUected at Dahas, Tex., August 22. The egg is dark-gray and thickly covered with spines. It measures 0.68 mm. in length and 0.21 mm. in breadth. The process at one end is frequently twisted. (Plate II, fig, 4.) Type IV. — This egg was practically identified as that of a Cato- laccus by isolation of specimens collected August 22 at Dallas, Tex. The color is white and the egg is covered with very small tubercles or papillge. It is 0.62 mm. long and 0.22 mm. broad. (Plate II, fig. 5.) Type V. — Tliis egg was taken only at Glenmora, La., August 23, on two weevil stages, and has not been identified. It is dark-gray and very spiny, but the spines are larger, longer, and sparser than in Type III. The length is 0.44 mm. and the breadth 0.19 mm. (Plate II, fig. 6.) Type VI. — This new type was discovered November 14 at Dallas, Tex., and has not yet been identified. There is no sculpturing what- ever. It is pure white. The length is 0.85 mm. and the breadth 0.19 mm. (Plate II, fig. 2.) THE LAEV^. The larvae of the boll-weevil parasites live as readily on dead food as on fresh food. The hosts generally die within a very short time after the larvse begin attack. The larvae have been found pretty well grown with dry weevil larvae as food. They have been found on weevil larvae and pupae indiscriminately and several times under the elytra of teneral or unemerged adults. Just before transforming from the larva to pupa there is considerable meconial discharge. The majority of the boll-weevil parasites are external feeders, but the larvae of Myiophasia senea, Ennyomma glohosa, and Tetrastichus Jiunteri are internal feeders. These larvae kill the host in a short time, its skin becoming shriveled and forming a perfect puparium for the parasite. Pupation takes place within this skin. (PI. Ill, figs. 5, 7.) Pupation. — All the chalcidoid parasites have naked pupae. The braconids usually form silken cocoons of characteristic size, shape, mesh, or color. The cocoons of Microhracon mellitor are very vari- able in size, color, and consistency, so that they appear almost to belong to different insects. The cocoons of Sigalplius curculionis are generally of a rather bright yellow and with very fine silk. The pupal exuvium of the various species of chalcids and braconids is sufficiently characteristic to enable a skilled observer to determine the species after the parasite has left. (PL III, figs. 1-4, 6.) Rapidity of development. — It is rather difficult to make an accurate study of the developmental period of parasites, especially when every adult parasite that matures under observation must be saved, if DEVELOPMENT OF THE PARASITES. 59 possible, for further experimentation or for determination. It is inadvisable to isolate many of the parasites until the larva is partially developed, as the isolation seems to dry out both food and larva. In the study of the parasites all those in the same stage were placed on the same tray. Wlien they passed to the next stage in develop- ment they were transferred to another tray. In this manner an accu- rate record was kept of the development. In order to determine the total length of the breeding period it seems best to take the total period from the collection of the material to the maturity of the last specimen and add a plus mark ( + ) to this figure. The total period can hardly be more than 2 or 3 days longer than the longest period thus obtained, as the egg period is very seldom more than 3 days. To obtain the exact length of the pupal period, the maxinnim period is taken to be the longest time from the observation of a fresh or newly-formed pupa to maturity, and the minimum time is taken to be the shortest period from the observation of the grown larva to ma- turity. Having thus accurately defined the pupal stage, the relative limits of the egg and larval stages are obtained by subtracting the pupal stage from the total developmental period. Table XX, which follows, presents all of the available data as they have been reduced in this manner to show the length of development of the various stages. It will be seen that most of the species ])ass their entire developmental period in from 20 to 30 days between June and October 15, but that after the middle of October the developing stages are caught by the cold weather and the development is sus- pended until spring. Thus, it is noticeable that parasites becoming larvae in early October and November have a short larval period of probably less than 20 days, becoming pupae before the cold wave and passing a pupal period of about 150 days. Parasite larvae which hatch a little later are caught in the larval stage and hibernate thus for from 120 to 150 days, then becoming pupa? and maturing in from 15 to 40 days. It will be noticed that Microbracon mellito?', Eurytoma tylodermatis, and the two species of Catolaccus have short developmental periods during the summer, while the species of Cerambycobius have a little longer period. It will be noticed that Hahrocytus inercSi has only appeared in the fall of the year. This species has been recorded four years in succession and never before October. On the other hand, Microdontomcrus anthonomi seems to be almost exclusively a summer parasite, having never been recorded after September. Of course the species of which we have records throughout the breeding season are the ones most important. This statement is borne out by the figures on the relative numbers and importance of the dift'erent species. 60 INSECT ENEMIES OF THE BOLL WEEVIL. Table XX. — Lengths of developmental periods of the holl-weevil parasites. Species and period. June. July. August Sep- tember Octobei 1-15. ■ October 15-30. Novem- ber. Decem- ber. Microhracon mcllitor: Egg and larva Days. 13-19 2-8 21 + Days. 0-8 5-7 13+ Days. 10-15 3-8 18+ Days. 0-10 4-8 14+ Days. 6-20 10-26 30+ 20+ 14+ 34+ 8-25+ 8-22 10-33+ 20-40 13 33-53 Days. 9+ 141-147 150+ Days. Days. 118+ 14+ 132+ 70+ 15 + 85 + 70+ Pupa Total 156+ 21 + 13+ 34-138+ Hahrocytus piercei: Egg and larva Pupa Total Calolaceus hunteri: Egg and larva 9-14+ 0-11 20+ 9-10+ 7-8 17+ 14-17+ 4-7 21 + 9-12+ 0-9 18+ 9-12+ 5-7 16-17 5-11 + 0-8 13-15 13-15 6-8 21 + 9-12+ 6-9 18+ Pupa 7-12 16+ 15+ 85+ Total Catolaccus incertus: Egg and larva Pupa.. Total 67+ Cerambycobius sp. : Egg and larva 65+ Pupa 18+ Total 83+ Cerambycobius cushmani: Egg and larva 13+ 3 + 16+ 6-9 10-13 19+ 11-10+ 4-9 20+ 4-10+ 6-12 16+ 16+ -12 28+ 15-19 7-11 26+ 7-11 + 7-11 18+ 16-20 8-12 28+ Pupa Total Cerambycobius cyaniceps: Egg and larva 10+ 9+ 19+ 18+ 7+ 25+ 84-113 Pupa 19-37 Total 129+ 139+ 191 150 Ennyomma globosa: Egg and larva Pupa Total Eurytoma tylodermatis: Egg and larva 11-12+ 5-6 17+ 12-25+ 5-9 21-30 15+ 11-36 5-6 17-41 8+ 8-11 10+ 8-9 7-8 16+ 11+ 15-23 26+ 158+ 20+ 178+ 110+ Pupa 17 25 Total 135+ Lariophagus tezanus Microdontor.icrKS an/honomi: Egg and larva 14-15 6-7 21+ 26 + 6-11 32-37 Pupa Total 20+ Myiophasia xnca: Egg and larva Pupa Total Pimpto sp.: Egg and larva 62+ Pupa 15- Total 87+ SigalpTius curculionis: Egg and larva 17-20+ 13-16 33+ Pupa Total Tctrastichus hunteri: Egg and larva 8-11+ 16-19 27+ 143-216+ 31+ 174-216+ Pupa Total Urosigalphus anthonomi: Egg and larva 6+ 9+ 15+ Pupa Total Urosigalphus sp. : Egg and larva 12+ 3 + 15+ Pupa Total DISTRIBUTION OF THE PARASITES. 61 8. THE DISTRIBUTION OF THE PARASITES. Parasites of the boll weevil have been recorded from eveiy part of the territory so far invaded. The records are so numerous that we are able to show statistically which are the most important para- sites of the weevil. The following list gives the species in their numerical rank for the entire period from January 1, 1906, to Jan- uary 1, 1910, giving only the number which were accurately deter- mined for each species. The first seven species are the most important, as has been shown in almost every section of this report. The last nine species may be considered as more or less adventitious or acci- dental. These species may possibly never be recorded again, or, on the other hand, they may become in the near future among the more important parasites. This very event has happened in the case of three or four of the other more important species. Up to 1906 only four of the first five in this list had been recorded from the boll weevil. The other species have been added since and some of them will become very important as the weevils enter the moister wooded regions of the East. ■ Tabi^e XXI. — Numerical rank of the parasites for the entire period, 1906 to 1910. Species. Microbracon mellitor Catolaccus hunteri Catolaccus incertus Eurytoma tylodermatis Cerambycobius cyaniccps. . . MicTodontomerus anthonom Tdrastkhus hunteri Cerambycobius cushmani. . . Sigalplms curcuUonis Habrocytus piercei Number of records. 2,147 1,094 578 575 574 302 168 76 37 36 Species. Ennyomma globosa Lariophagus tetanus Myiophasia xnea Eurytoma sp Cerambycobius sp SpilocKalcis sp Urosigalphus anthonomi Urosigalphus sp Perilampus sp Pimpla sp Number of records. A study of the value of these parasites by years has shown that the majority of the species had not occupied the same rank in two successive years. The accompanying diagram (fig. 13), giving the yearly rank of the boll- weevil parasites from 1906 through 1909, shows that in each year new parasites were recorded and that in some cases these parasites continued to attack the weevil. Microbracon mellitor appears to vary but little in importance in different seasons, while Catolaccus hunteri shows increasing importance year by year. Some of the other parasites of considerable importance appear extremely variable in their relative rank. It will be noticed that Habrocytus piercei has occupied the ninth place three years in succession and is now in eighth place. This parasite occurs in small numbers, but may at any time become a leading parasite in Louisiana and Missis- sippi. In addition to giving the yearly rank of the species this diagram also shows the proportion of the sexes observed each year. 62 INSECT ENEMIES OF THE BOLL WEEVIL. In order to show the regions in which the various species are of greatest importance, the accompanying map (fig. 14) is presented. This shows that while Microhracon mellitor has yielded more individuals than the other species, it is the predominating parasite in by far the larger proportion of the infested territory. It can also be seen that much more can be expected from the other parasites as the weevil moves eastward into their territory. Microdontomerus anthonomi is quite important throughout the central black-prairie region of Texas. Eurytoma tylodermatis is more important in north-central Texas and also in the coast region of Texas, Ceramhjcohius cushmani is charac- 1906 1907 B/7AC0yV »etj. ITOff 1908 BMCWMec I /Toff 1909 9 l£l> Fig. 13.— Diagram Illustrating yearly rank of the boll weevil parasites, 1906, 1907, 1908, and 1909. (Original.) teristic of the counties grouped around Victoria County, Tex., but a few specimens have been reared from the boll weevil at Alexandria, La., by Messrs. Cushman and Jones. 9. THE PARASITE SEASONS. For the convenience of this work on parasites of the boll weevil, the year has been divided into definite parasite seasons correspond- ing with certain groups of conditions. The year opens with the Mhernatio7i period well underway. In so far as the parasites are concerned those which hibernate as immature insects mature gen- erally about the middle of March. This marks the end of the hiber- THE PAKASITE SEASONS. 63 nation period or winter season and the opening of the spring season. From March until the middle of June or sometimes July there are no cotton squares for the weevils to breed in. Consequently the para- sites are obliged to seek other hosts. The summer season is defined as beginning with the production of squares in which the weevils and their parasites may breed. Thus this season continues until squar- ing ceases — that is, until late in the fall when cotton is killed by frost and is succeeded by the winter season. However, we frequently dis- tinguished a fall or postmigration season, which begins with the first Fig. 14.— Map showing the distribution of the more important parasites of the boll weevil. (Original.) attack of weevils upon the bolls in August and ends with the heavy frosts in October or November. The fall season is also character- ized by a renewed growth of squares. I. THE HIBERNATION OR WINTER SEASON. The most important parasites which winter as immature stages upon the boll weevil are Microbraconmellitor,Catolaccus hunteri, Ceram- bycobius cyaniceps, Eurytoma tylodermatis, TetrasticJms hunteri, and Habrocytus piercei. The last two species are characteristic of winter examinations in Louisiana and Mississippi. The predatory 64 INSECT ENEMIES OF THE BOLL WEEVIL. coleopterous larvae Hydnocera puhescens LeConte and H. pallipennis Say are very frequently found hibernating as larvse in the boll- weevil cells or in the cocoons of Microhracon mellitor. The stage in which these various parasites pass the winter is given very concisely in the table of the developmental periods (Table XX) in section 7. During January, 1910, Mr. Hood repeatedly found Eurytoma tylo- dermatis and Catolaccus Jiunteri hibernating in dry cotton squares and bolls and especially in hanging moss at Mansura, La. II. THE SPRING SEASON. It has been demonstrated that there is a definite period between the hibernation season and the first infestation of squares, extending from the middle of March to the middle of June. What happens to the parasites during this period is of considerable importance and a great amount of work has been done in the search for intermediate hosts. In the case of Catolaccus hunteri the question was very satisfac- toril}?^ answered. At Richmond, Tex., a large number of dewberry buds infested hy Aritlionomus sif/7iatus was gathered March 21, 1907, and this species of parasite was reared continuously between March 28 and April 1 . At Victoria, Tex., Mr. J. D. Mitchell collected, on April 23, 1907, a lot of haws {Crataegus mollis), infested by TacJiypterellus quadrigihhus, and on May 7 he reared this species of parasite. In- vestigations as to the distribution of these weevils added to the formerly laiown records of AntJionomus signatus in dewberry buds: Natchitoches and Shreveport, La.; Texarkana, Ark.; Muskogee and Ardmore, Okla. ; and Trinity, Richmond, Waco, Dallas, and Mar- shall, Tex. TacTiypterellus quadrigihhus was found breeding at Shreveport and Natchitoches, La., and Victoria, Tex. At Dallas, Tex., the buds of Galpinsia liartwegi were found to be infested by Auleutes tenuipes as early as April 24. This species is a host of several species of Catolaccus. The buds of Callirrhoe involu- crata were found at Dallas to be infested by AntJionomus fulvus as early as April 1, and on the same date Anihonomus seneolus was first observed to be breeding in the buds of Solanuiri torreyi. Solanum elseagni folium, with AntJionomus seneolus both in its buds and in the fungus leaf-galls, and Solanum rostratum with this weevil in the buds, appeared early in April. All of these plants continued susceptible to weevil work up to the end of the spring period, or until cotton began to square. Numerous specimens of Catolaccus were reared from the Solanum-infesting species of Anthonomus. MyiopJiasia senea was reared April 11, 1907, from ConotracJielus elegans in galls of PJiylloxera devastatrix on the petioles of Hicoria THE PARASITE SEASONS. 65 pecan, collected April 2, 1907, at Victoria, Tex., and was reared June 5, 1907, from material collected May 4 at Dallas. Sigalphus curculionis was reared in considerable numbers between April 28 and May 7, 1907, from Conotraclielus nenuphar in plums gathered at Texarkana, Ark., March 26; and between April 29 and May 17, 1907, from Conotrachelus elegans in galls of Phylloxera devas- tatrix on pecan, collected at Victoria, Tex., April 2; also between June 5 and 14, 1907, from the same species in material collected at Dallas, Tex., May 4. Ceramhycohius cyaniceps was studied very carefully at Victoria, Tex., by Mr. J. D. Mitchell during the winter of 1909-10 as an enemy of Trichoharis texana in stems of Solanum rostratum, antl of Lixus scrohicollis in stems of Ambrosia trifida. Mr. T. T. Ilolloway conducted experiments in longevity by feedmg sugared water to the parasites. Emergence began, in the lots of Trichobaris, on February 1 and continued until April 8. The last parasite lived until May 31. The total period of activity was 119 days and the average period lasted from March 11 to April 1. The longest record of longevity was 71 days and the average 21 days. Emergence began from the lots of Lixus on March 2 and continued until March 24. The last parasite lived until May 11. The total period of activity was 70 days and the average period was between March 13 and April 4. The longest record of longevity was 67 days and the average 22. Eurytoma tylodermatis was reared from the same lots and treated in the same manner. Emergence began from the lots of Trichobaris on February 3 and continued until March 21. The last parasite lived until April 30. The total period of activity was 86 days and the average period was between March 10 and March 30. The longest record of longevity was 42 days, and the average 20 days. Emergence began from the lots of Lixus on February 22 and lasted until April 17. The last parasite lived until June 1. The total period of activity was 99 days and the average period lasted from March 16 to April 11. The longest record of longevity was 79 days and the average 26 days. III. THE SUMMER SEASON. TJie first boll-weevil ])arasites of the year are reared late in May or early in June in southern Texas, but in a very short time squares are forming all over the entire cotton belt and parasites may be found everywhere in small numbers as the summer progresses. The per- centage of parasitism increases rapidly and generally becomes very high after August 1. Most of the important parasites may also be found on their normal summer hosts. 16844°— Bull. 100—12 5 66 INSECT ENEMIES OF THE BOLL WEEVIL. About the middle of August squares commence to fail, and few squares are to be found by September 1. This condition may be said to begin the fall season, when the parasites are largely obliged to seek other hosts or to attack the boll weevil in bolls. IV. THE FALL OR DISPERSION SEASON. Coincident with the decline in square production is the begimiing of the boll-weevil dispersion which extends into new territory around the entire periphery of the infested region. In the fall there is a new growth of squares which furnishes food for the weevils before entering hibernation and also furnishes an opportunity for very high parasitism just preceding hibernation. It is during this season that parasite swarms are recorded and hence this is a very critical time for obtaining and transferring desirable parasites to new regions. During this early fall season there are several very important ways of propagating the parasites already present in the vicinity, as will be shown later. The fall season of the year closes abruptly with the first killing frost, for this crisis precipitates the hibernation period. 10. ADJUSTMENT TO NEW HOSTS. It is a very strildng fact that the continuously breeding boll weevil is attacked by parasites which in many instances attack nor- mally weevils having but a single generation annually. Some of these parasites attack one host after another throughout the entire breeding season and may be found in activity at all periods except during hibernation. This condition is well illustrated by the accompanying diagram (fig. 15) giving the seasonal rotation of Catolaccus hunteri and Ceramhycohius cyaniceps. Whether these parasites were origi- nally single-generation species like their hosts is a question we can not now decide, but we now know that they have become adapted to many species. This fact can be most easily proven by reference to the list of hosts of the boll-weevil parasites given in the second section of this part (p. 42). It appears possible that the constantly changing factors of nature cause the various species to be continually adjusting their habits to new environments and new hosts. In other words, the groups of parasites from wliich the most available enemies of a new or introduced species may be obtained are those groups in which the parasitic habits are the most variable. A parasitic species that is as readily at home on a stem weevil as on a bud or seed weevil is probably able to attack many different species. The most striking example of the adjustment of new parasites was furnished in 1907. A lot of hanging squares collected by ]\Ir. J. D. Mitchell on August 5, 1907, at Victoria, Tex., on a field known as the Haskell field gave a percentage of 61.5. There was something so ADJUSTMENT TO NEW HOSTS. 67 striking about the nature of the record that Mr. C'ushman was sent immediately to Victoria to study the surroundings of this field and report upon the possible reasons for the high percentage of parasitism. Mr. Cushman reported after considerable study that there were only two factors which, it seemed to liim, might have an influence upon the parasites of the boll weevil. The fii-st factor was the com- plete lack of fruit upon the huisache trees (Vachellia farnesiana) which is the normal food of Laria saUsei. The second factor noticed was the absence of flowers on the Callirrlioe involucrata, the host of Anthonomus fulvus. 'Mr. Cushman reasoned that the point would be proven if we should rear from the boll weevil some of the character- istic parasites of either this or the other species. As a result of rearings from the material collected in this field, the prmcipal par- asite was Microbracon meUitor, the typical boll weevil parasite, but a S^ASOA/AL ROTAT/Oa/ OF HOSTS BV CaTOLACCUS HUNTERI CPAWfOffD. JA/VUARy FEBRUAfly MARCH APRIL . MAY- JCA/er ^ULY AUGUST SEPTEMBER OCTOBER fJOVEMBER DECEMBER Anthonoi fUS GfiAfJ,. An/THCW OMUS S/g) lATi/S SAy ifVLus Bo. VCMAA/ ■HONOMUS 6RAAJD/6 BOHEM^ AJ Tachw VS BoHEn; Af^THOf VOMUS A£/l -oferLws Q /ADR/C/B8U s Sav A/v Smicraui AX TUBEP :ULATC/S /■ /'^fljrHO^OMt^S ALBOP/L OSUS D/E fe ICRCULATU- S P/ERCE A yrno/^OMU. ~ ncrcf>OTf ECAi: P/SK SM/Cf AUtAx ru, SeASO/\JAL ROTAT/OAT OF HOSTS BY CsRAMBYCOB/US CYA/V/CFPS ASHMEAD. TACHyPTE ReLLljIS n QUAORi GI6BUS . 1/XU3 SOfOB/COLlfe BOHEMAr j Smicrau^a AXTVBE'XWATUS PlERCE CfMjs soRD/pus LeCcvte Trichc baris CO ■JtP^CTA Casev A/VTl lONOMUS Aa/THO^OMCS GRAA/a/S BoHE/y.^M R/s ro'AA/A Lsao/vrE L/XUS SCROB/COLL.S BOHEf^.AA/ SM/Cf^AUlAX ThBERCaLAfl/S P/ERCl Fig. 15.— Diagram illustrating the seasonal rotation of hosts of Catolaccus hunteri and Cerambycobius cyaniceps. (Original.) species which is also a typical parasite of Anthonomus fulvus. It is probable that the latter species furnished some of the Micro- bracons for this infestation. The next most important species was Cerarnbycohius cushmani, a typical parasite of Laria sallxi and of Arxcerus fasciculatus which breeds in the fruit of the chinaberry tree {Melia azederach). In addition to this species, this same field yielded 3 other new parasites of the boll weevil, 2 of which are known to be parasites of the Laria. These were Eurytoma sp., Spilochalcls sp., and Lariopliagus texanus. To illustrate the divergence of habits among parasites the host relations of Catolaccus incertus may be cited. This parasite attacks several species of Laria (Bruclius) which are internal seed eaters and pupate in their feeding cells; such weevils as Zygoharis lantlioxyli and Auleutes tenuvpes, which are seed or bud feeders and pupate in the 68 INSECT ENEMIES OF THE BOLL WEEVIL. ground; and Anthonomines, which dwell in buds {Anthonomus gran- dis), in flowers {A. aplianostejilii) , and in hard seed (A. alhoinlosus). But it draws the line apparently at stem dwellers and is replaced by Neocatolaccus tylodermse on Lixus, Tyloderma, and Ampeloglypter. Ceramhijcohius cyaniceps is as much at home in a stem as in a bud, and so also are Eurytoma tylodermatis and Microdontomerus anthonomi. The Braconidse appear to be more particular as to food but the most noted of all, Microhracon mellitor, has no preferences between stem dwellers and bud dwellers. Thirteen miles southeast of Yazoo City, Miss., on November 1, 1909, the senior author found an isolated artificial focus of infestation by the boll weevil over 30 miles from any infestation of the same age and 20 miles beyond the regularly infested region. Out of 8 squares picked, containing 5 stages, 1 parastized stage was found. 11. BEETLES WHICH PREY UPON THE BOLL WEEVIL. The attack of the insects predatory on the adult boll weevil is purely accidental. They may be very numerous, but the only ones recorded and verified are Evarthrus sodalis Le Conte and another species of the same genus. There are, however, several insects which have an actual value through their established habit of either breeding in the square upon the boll-weevil stages or of entering the square and consuming the weevil. We shall refer to four of them. Hijdnocera 'pallvpennis Say. A single beetle of this species was reared April 6, 1907, after 183 days in its cocoon, and over 214 days isolation in the rearing tube. It was collected in a boll-weevil cell at Waco, Tex., August 28, 1906. The cocoon is very finely threaded, loosely woven, and only single layered. The stage of the beetle can easily be observed at any time. Hydnocera pmhescens Le Conte. This clerid is a very common breeder in the weevil cells. Its larvse have been found not only feeding upon the various weevil stages but have been taken frequently from IVIicrobracon cocoons which they have entered at a much younger stage. Cathartus gemeUatus Duval. Tliis cucujid beetle is both a predator and a scavenger, its larvse being frequently found, however, feeding upon boll-weevil stages which they must have killed. Chmdiognathus spp. The larvae of these lampyrid beetles are very common in the squares and bolls of cotton in Louisiana and Missis- sippi. In one instance undoubted proof of the attack of such a larva upon one boll- weevil larva was recorded. Many other very sus- picious observations were made but no definite proofs found. ANTS WHICH PREY UPON THE WEEVIL. 69 12. LEPIDOPTEROUS LARV^ WHICH ARE INCIDENTALLY PREDATORY UPON THE BOLL WEEVIL. Alabama argillacea Iliibner. The cotton leaf caterpillar is distinctly an enemy of the boll weevil and of considerable importance. When it defoliates a cotton field a month or more before the frosts it often destroys immature weevils in the cotton squares and cuts off the entire food supply of the adult weevils remaining. These weevils may be able to suspend their activities and begin hibernation but it is well known that weevils entering hibernation early in the fall can seldom survive a long hard winter, or live until cotton is up in the spring. Those that can not hibernate either die of starvation or rise in flight to seek cotton elsewhere and may perish in the efl'ort. It is presumed that a very high percentage of fljing weevils fails to find cotton. The leaf worm is attacked by 18 predatory bugs, 16 predatory beetles, 6 predatoiy wasps, and the following ants: Dorymynnex pijramicus jlavus McCook, Forelius maccooki Emeiy, Solenojms geminata Fabricius (these three ants are enemies of the boll weevil) and Monomoi'ium carhonarium. Smith. Ten hymenopterous parasites and one hyperparasite are known, and in addition the leaf worm is attacked by a predatory fly and by two parasitic flies. 13. ANTS WHICH PREY UPON THE BOLL WEEVIL. HYMENOPTERA. DORYLID.E. Eciton (Acamatus) commutatum Emeiy. This ant was taken by Mr. C. R. Jones at Beeville, Tex., attacking the boll- weevil larvae in squares. Dr. W. M. Wlieeler states that it is commonly parasitized by a round worm of the genus Mermis. PONERID^. Edatomma tuberculatum Olivier. The "kelep," or so-called Guate- malan ant, is a native of Mexico and Central America. Like all other ponerids it is slow in action. The mnters have proven too severe for any of the imported colonies. The rate of development is so slow and the movements of the adults are so sluggish that little could be hoped for from this species even if it could become accli- mated in this countiy. MYRMICID.E. Cremastogaster lineolaia (Say) var. clara Mayr. This ant is also an enemy of the boll weevil, having been recorded attacldng immature stages at Dallas, Tex., by Dr. W. E. Hinds. It has frequently been seen in the rearing cage carrying off insect prey. The species lives 70 INSECT ENEMIES OF THE BOLL WEEVIL. in hollow stems, sticks, and galls and is commonly seen at the necta- ries of cotton or attending aphides, membracids, etc. Prof. F. E. Brooks has recorded this ant as an enemy of Heliotliis obsoleta, the cotton boll worm. Solenopsis geminafa Fabricius. The ''fire ant" (fig. 16) is very common in Texas cotton fields, where it is always an enemy of the boll weevil, as well as of the cotton bollworm {Heliotliis obsoleta) and tlie cotton leaf worm {Alabama argiUacea). In Louisiana, Arkansas, and Mississippi it is very seldom seen in cotton fields, except in soiitliern Louisiana, where unfortunately it is in danger of extermination by the Argentine ant, Indomyrmex hmnilis Mayr. This species divides credit for the greater part of the ant control of the boll weevil with the other species of Solenopsis, two species of Monomorium, and with the various spe- cies of Pheidole. Its nests are placed in the cotton fields, generally near the base of the plants, and from these the foragers go out in all directions in search of food. The workers have learned to detect the presence of the boll weevil in the squares and in a short time can effect an entrance into the wee^nl cell from which they either draw the weevil bodily or convey it in parts to their nests. This ant is some- times found on the plant, but most com- monly it does its work on the ground. The species is parasitized by {Pseudac- teon) Plastoyliora crawfordi Coquillett at Dallas, Tex. Solenopsis molesta Say {dehilis Mayr) . This minute ant was taken in the act of attacking a boll-wee^dl larva by Mr. Cushman at McAlester, Okla. This species and the next are so similar in appearance that they may be easily confused. Prof. F. E. Brooks has recorded it as an enemy of Craponius insequalis. Solenopsis texana Emeiy. This minute ant is a common enemy of the boll weevil in Texas, Louisiana, and Mississippi. The entrance holes are very minute, but sometimes the ants enter the squares in great numbers. On October 31, 1907, at Thornton, Tex., Mr. Cushman found 85 individuals attacking a weevil larva in a single square. It is mentioned in the investigation records as attacking the weevil at Alexandria and Monroe, La., and Cuero, Lampasas, and Llano, Tex. It is also recorded as an enemy of Heliotliis obsoleta. Monomorium 7ninimmn Buckley. This common house ant (fig. 17) is a very valuable enemy of the boll weevil and is common in cotton Fig. ]6.— The "fire ant" {Solenopsis geminata), an enemy of the boll weevil: Worker. Enlarged. (From HiTnter and Hinds.) ANTS WHICH PREY UPON THE WEEVIL. 71 fields. It is recorded in the Dallas collection as attacking the boll weevil at Llano, Lampasas, Albany, Henrietta, Arlington, and Dallas, Tex., Euston, La., and Roxie and Port Gibson, Miss. The species has been taken attacking the immature stages of Trichobaris com- jyada, Antlionomus alhopilosus, and Anthonomvs fidvns. It generally attacks these weevils as well as the boll weevil on the plant, entering the infested bud or square in search of its food. Monomonum iDliaraonis L. This cosmopolitan house ant (fig. 18) is another of the most important boll-weevil enemies, being very Fig. 17.— The little black aiU (Mundinoriiim minimuin), an euemy of the boll weevil: a. Fe- male; 6, same with win^s; c, male; d, workers; e, pupa; /, larva; g, egg of worker. Enlarged. (From Marlatt.) abundant in the cotton fields of certain sections. It is represented in the Dallas collection as attacking the boll weevil at Victoria, Tex.; Fosters, Ruston, and Monroe, La., and Camden, Ark. It also attacks the weevil on the plant. In southern Louisiana it is being exterminated by the Argentine ant (Iridomyrmex Jiumilis). Pheidole sp., near Jlavens. At Arlington, Tex., August 31, 1908, Mr. Cushman found abundant evidence of the control of the boll weevil by this species. It attacks the weevil larvae both on the plant and on the ground. 72 INSECT ENEMIES OF THE BOLLi WEEVIL. Pheidole crassicornis Emery. At Lampasas, Tex., September 23, 1908, Mr. Ciishman found this ant a very abundant enemy of the boll weevil. DOLICHODERIDiE. Forelius maccooH Forel. At Beeville, Tex., August 13, 1906, Mr. C. R. Jones found a high mortality of the boll weevil due to this species. Dr. Wlieeler has recorded the fact that this ant prefers bare, dry ground for its nests. The species also attacks Alabama argillacea and Heliothis ohsoleta. On September 7, 1908, at Dallas, Tex., Mr. F. C. Bishopp took specimens in the act of attack, and September 21, 1908, Mr. Cushman took others at Llano, Tex., attack- ing the weevil. Dorymyrmex injra.inicMs Roger, the "lion ant," protects solitaiy tree cotton from the boll weevil in Cuba (Schwarz, 1905). Fig. 18. — The little red ant {Monomoriwm pharaonis), an enemy of the boll weevil: a, Female; b, worker. Enlarged. (From Riley.) Dorymyrmex pyramicus (Roger) var. flavus McCook. This com- mon ant of the cotton fields has only once been taken as an enemy of the boll weevil, namely at Texarkana, Tex., by Mr. R. C. Howell, but its abundance would make it a very important species if it should develop a fondness for weevil larvse. It is an enemy of Alabama argillacea and Heliotliis obsoleta. Iridomyrmex analis Andre. Specimens of this ant were found attacking the boll weevil by Dr. W. E. Hinds. This species is nor- mally a honey ant, but occasionally takes insect food. It is veiy common in cotton fields, especially in Louisiana. Iiidomyrmex humilis Mayr. The much-feared Argentine ant has been taken attacking the boll weevil. It is, however, a friend to the weevil because it exterminates Solenopsis geminata, Monomorium pharaonis, smd Iridomyrmex analis (Foster, 1908). BIOLOGY OF TPIE COHOSTS. 73 FORMICIDiE. Formica fusca (Linnaeus) suhpolita (Mayr) perpilosa Wheeler. This species of ant is normally a honey feeder, but it is recorded by Rangel (Rangel, 1901c) as a predator on adult boll weevils in Mexico. Formica pallidi-fulva Latreille. A single instance of this species cutting its way into a square infested by a boll weevil was observed by Mr. Hood at Ashdown, Ark., September 2, 1908. Prenolepis imparis Say. A single instance of this species cutting its way into a square infested by a boll weevil was observed by Mr. Hood at Ashdown, Ark., September 2, 1908. 14. BIOLOGY OF THE COHOSTS OF THE BOLL-WEE^^L PARASITES. The biologies of the parasites concerned in the boll-weevil complex have already been discussed. It now remains to consider the native weevils which have already or may later enter into the complex of cohosts of the boll-weevil parasites. Many of these weevils are native to the territory already occupied by the v-eevil, while others will become important as new territory is added. Other families of Coleoptera and even other orders of insects may later be found to be of more or less importance as cohosts of boll- weevil parasites. The late Dr. William H. Ashmead stated that Microhracon meUitor had been reared from many Coleoptera, while Ceramhycohius cyaniceps bred in cerambycids and other beetles. It is important also to note the record of Ceramhycohius cyaniceps from Languria. Our own observations have been confined to the Coleoptera of the families Lariidse, Anthribidas, and Curculionidse. PHYTOPHAGA. LARIID^. (BrudiusY Laria sallxi Sharp. Tliis bruchid is characteristic of the Gulf Coast prairie of Texas. It breeds in the pods of huisache ( VacJielliafarnesiana) , is a continuous breeder, and is generally highly parasitized by Urosigalplius hruclii, Ceramhycohius hruchivorus , Cer- AMBYCOBIUS CYANICEPS"; CeRAMBYCOBIUS CUSHMANI, LaRIOPHAGUS TEXANUS, EuRYTOMA TYLODERMATis, Horlsmeuus sp., and several other undetermined parasites. Laria exigua Horn. This bruchid is apparently Austroriparian and Carohnian. Its principal food plant is Amorphafruticosa, in the seed 1 The generic name Bruehus was first used bj' Geoffroy in 17G2. Only one species is admissible in our code of nomenclature and this is C erambyx f ur'Lhm.xxis, which is also the type of Ptinus Linnaeus 1707. The genus Laria was described by Scopoli in 1703 and the type thereof has been designated as salicis Scopoli, a synonym of Derincstes pisorum (pisi) I^innteus. Linnseus's conception of Bruehus dates from 1707 and the type thereof was designated by Latreille (1810) as Dcrmestes pisorum Linnasus. Hence we see that Bruehus Linnaeus (1758) Is preoccupied by Geoflroy (1752) and an isogenotypic synonym of Laria Scopoli (1703). Although the genus has been subdivided into several genera, our American species have not been studied with regard to such subdivision and it is hence best to consider all as iu the genus Laria, sensu latiore. s The names of boll-weevil parasites are printed in small capitals; others in itaUcs. 74 INSECT ENEMIES OP THE BOLL WEEVIL. pods of which it breeds prohfically. It is a continuous breeder and is highly parasitized by Ceramhycohius hrevicaudus , Cerambycobius CYANiCEPS, Ilorismenus sp., Reterosiy'tlus 'prosoindis, Eurytoma sp., MiCRODONTOMERus ANTHONOMi, Catolaccus incertus, and Several other species. Laj'ia ohtecta Say. The common bean v.'^ecvil is known to be para- sitized by Cerambycobius cyaniceps and Bruchohius laticolUs. Laria comfressicornis SchaefFer. This bruchid, which breeds in the pods of Acuan illinoensis , is parasitized by Cerambycobius cy- aniceps and Heterospilus prosojndis. Laria ocliracea Schaeffer. This bruchid, which breeds in the pods of Vicia sp., is parasitized by Cerambycobius cyaniceps, C. cush- mani, Eurytoma sp., and Heterospilus j^rosopidis. Spermophagus rohinke SchaefTer. This bruchid is very common in the pods of the honey locust (Gleditsia triacantlios) , and the water locust {Gleditsia aquaiica), both of which are trees belonging to the humid Austral zones. It is parasitized by Heterospilus hrucJii, Cer- ambycobius cyaniceps, Eurytoma tylodermatis, and TJrosigalpJius hrucM. RHYNCHOPHORA. ANTHRIBID.K. BracJiytarsus alternatus Say. This beetle probably breeds under many different circumstances. The only records are from a fungus gall on Ipomcea pandurata, and from the stems of Elymus virginicus and Sideranthus rubiginosus. It apparently belongs to the humid Austral zones. It is parasitized by Microdontomerus anthonomi and a Bracon. Arsecerus fasciculatus DeGeer. This very mdely distributed Lower Austral insect (see fig. 19), known commonly as the coffee- bean weevil, breeds in stored vegetable prod- ucts, in the seed of TTieohrojna cacao, in the berry of the coffee tree {Coffea ara- bica), in diseased cotton bolls, in seed pods of Cassia occident- alis and C. oh- tusifolia, in seeds of Indigqfera tinctoria, in green and decaying fruit of Melia azedarach, in green and dry cornstalks, and in dry acarian galls on Ipomcea Fig. 19. — The coffee-bean weevil (Arscccnis fasciculatus) , a cohost of boll- weevil parasites: a, Larva; b, adult; c, pu\rA. Enlarged. (From Chit- tenden.) BIOLOGY OF THE COHOSTS. 75 lacunosa. In the Melia berries it is parasitized by Cerambycobius CUSHMANI, EURYTOMA TY'LODERMATIS, and PeDICULOIDES Sp. CURCULIONID.E. APIONIN.E. Apion seg.ni'pes Say in Cracca virginiana is parasitized by Eury'- TOMA TYLODERMATIS. A'pion decoloratum. Smith. Dr. Cliittenden records this weevil as breetUng in Meihomia paniculata and parasitized by Catolaccus INCERTUS. A'pion griseum Smith. Dr. Chittenden records this weevil as breeding in Phaseolus retusus, P. wriglitii, P. polystachyus, and StropJiostyles paucifiora, and parasitized by Catolaccus incertus. Apion nigrum Smith. Breeds in buds of Rohinia pseudacacia and is parasitized by Catolaccus incertus. Apion rostrum Say in pods of Baptisia is parasitized by Ceramby'- COBIUS CYANICEPS. CLEONIN^. Lixus musculus Say. This weevil is known both from the Lower Sonoran and Austroriparian zones. It breeds in the stems of Poly- gonum pennsylvanicum, P. portoricense, and P. punctatum, maldng an oblong gall or swelling. It is parasitized by Eury^toma ty'lodermatis, Ceramby'cobius cy'aniceps, Neocatolaccus tylodermx, GlyptomorpTia rugator, G. novitus, and Horismenus lixivorus. Lixus scrohicoUis Boheman. Tliis weevil (fig. 20) is probably confined mainly to the moist Austral zones. It breeds abundantly in the stems of Anibrosia trijida, A. artemisisefolia, A. psilostacJiya, and Ilelianthus spp. It is c[uite highly parasitized hy Ptinohius magnijicus , EURY'TOMA TYXODERMATIS, CeRAMBYCOBIUS CY^ANiCEPs, Glyptomorpha rugator, G. mavaritus, G. lixi, Vipio helfragei, Microdus simillimus, and Horismenus lixivorus. Mr. Townsend has described Lixopliaga parva from a specimen reared from this weevil at Dallas, Tex., August 15, 1907. Fig. 20.— The blood weed weevil (jLijhs scrobicollis) , a cohost of boll-weevil para- sites. Enlarged. (From Hunter and Hinds. 1 ERIRRHININ^. Smicronyx tycTioides LeConte. This weevil breeds in stem galls of various species of Cuscuta. It is parasitized by Microbracon mel- LiTOR and Eutrichosonia alhipes. 76 INSECT ENEMIES OP THE BOLL. WEEVIL. Desmoris scapalis LeConte. This weevil (fig. 21) occurs mainly on the black prairie in Texas and breeds in the heads of SiderantTius ruhiginosus. It is parasitized by Microbracon mellitoe. ANTHONOMIN.E. Macrorlioptus sphseralcix Pierce. This weevil was found breeding in stems of Sphseralcea angustifolia. It is the host of Eurytoma TYLODERMATIS. TacJiypterellus guadrigihhus Say. This fruit weevil breeds in the seed of apple, pear, Cratsegus oxyacantha, and Cratxgus mollis. It is known to us to be parasitized by Cerambycobius cyaniceps and Catolaccus hunteri. Smicraulax tuherculatus Pierce. This species breeds in the stems of mistletoe (Phoradendron iiavescens) throughout Texas, and evi- dence of its work has been observed in Louisiana and Mississippi. It is parasitized by Eurytoma tylo- DERMATis, Cerambycobius cyani- ceps, Catolaccus hunteri, and jMicrobracon mellitor. Anthonomus fiilvus LeConte. This weevil breeds in the larger l^uds of Callirrhoe involucrata and C. digitata. It is a characteristic woodland and meadow insect in Oklahoma and Texas . The known parasites are Catolaccus incer- Tus and Microbracon mellitor. Anthonomus signatus Say. The strawberry Aveevil is mainly char- acteristic of the humid Austral zones, and it breeds in the buds of strawberry, blackberry, dewberry, raspberry, Rubus viUosus, Poten- tilla canadensis, and Cercis canadensis. It is parasitized by Micro- hracon anihonomi, Calyptus tihiator, Catolaccus hunteri, C. incer- tus, and C. anthonomi. The two latter species were described from this weevil. Anthonomus cdhopilosus Dietz. This little Texas weevil breeds in the capsules of Croton capitatus, O. engelmanni, and C. texense. It is known to us to be parasitized by Microbracon mellitor, Cato- laccus hunteri, C. incertus, and Cerambycobius cyaniceps. Anthonomus nigrinus Boheman. This species is eastern in habitat and breeds in the buds of Solanum carolinense, and the potato {S. tuberosum). It is the host of Entedon lithocoUetidis, Eriglyptus rohustus, Catolaccus incertus, and C. anthonomi. Fig. 21.— The iroiiweed weevil (Desmoris sea. palis), a cohostof boU-weevil parasites. En- larged. (From Hunter and Hinds.) BIOLOGY OF THE COHOSTS. 77 Anthonomus seneolus Dietz. Tliis Texas weevil breeds commonly in fungus galls on the leaves and in the buds of Solanum eleagnifolium and S. torreyi and also in the buds of S. rostratum. It is parasitized by Catolaccus hunteri and a Eurytoma. Anthonomus eugenii Cano (xneotinctus Champion). The pepper weevil (fig. 22) breeds in most of the cultivated and wild peppers and may be considered a serious pest. It is parasitized by Catolac- cus HUNTERI, Microbracon mellitor, and Pediculoides ventri- cosus. Anthonomus squamosus LeConte. Tliis is a weevil typical of the gypsum prairie of the Lower Sonoran Zone, although occurring less abundantly in the western edge of the moist Austral zones. It breeds in the flower heads of Grindelia squarrosa nuda, G. inuloides, and perhaps also on other Grindelias and Heliantlii. It is known to us to be parasitized by Microbracon mellitor, Catolaccus iiunteri, and Eury- toma TYLODERMATIS. Anthonomus nebulosus LeConte. This wee- vil breeds in the buds of Crataegus in Louisi- ana and Arkansas. It is parasitized by Cato- laccus HUNTERI and Sigalphus sp. Anthonomus heterothecx Pierce. This small weevil breeds in the flower heads of Hetero- theca suhaxillaris and probably other asteroid flowers. It is parasitized by Catolaccus HUNTERI and Eurytoma tylodermatis. Previous records by the senicn* author on Anthonomus disjunctus LeConte all refer to this weevil. Anthonomus aphanostephi Pierce. This weevil breeds in the heads of Aphanostephus slirrohasis, and is parasitized by Catolaccus incertus. Fig. 22.— The pepper weevil {Anthonomus eugenii) , a cohost of boll-weevil parasites. En- larged. (From Hunter and Hinds.) TYCHIIN.E. Tycliius sordidus LeConte. This Austroriparian weevil breeds in the pods of Boptisia hracteata and i>. leucantha. It is ])arasitized by Cerambycobius cyaniceps. CRYPTORHYNCniN^. Chalcodermus seneus Boheman, the common cowpea weevil (fig. 23), is abundantly parasitized by Ennyomma globosa, and is likewise a host of Ennyomma clistoides and Sigalphl^s curculionis. Conotrachelus affinis Boheman. This weevil breeds in hickory nuts and is parasitized by Myiophasia iENEA and Sigalphus curculionis. 78 INSECT ENEMIES OF THE BOLL WEEVIL. Fig. 23.— The covvpea weevil {Chalcodermus seneiis), a cohost of boll-weevil parasites. Enlarged. (From Chittenden.) Contraclielus juglandis LeConte. This is the walnut weevil, wliich. is also parasitized by Myiophasia .^enea, Cliolomyia inxquii^es, Meta- dexia lasalis, and Sigalphus cuhculionis. ConotracJielus elegans Say. This weevil breeds abundantly in the petioles of hickoiy, the galls of Phylloxera devastatrix on pecan, in pecan nuts, in leaf rolls on liickory, and finally in the roots of Amaranthus retro- jiexus. It is fre- quently parasitized by Myiophasia ^nea and Sigalphus cur- cuLiONis, and occa- sionally by Cliolomyia insequipes. ConotracJielus nen- uphar Herbst. The common plum curculio (fig. 24) breeds in the pulp of drupes and pomes. The larvse are parasitized by Cholomijia inxquipes, Sigal- phus cuRCULiONis, MicROBRACON MELLiTOR, and Povizon conotracheli, and the eggs by Anaphes conotracheli. ConotracJielus naso Le- Conte. The common acorn weevil is para- sitized by Sigalphus CURCLTLIONIS. Tyloderma foveolatum Say. This common wee- vil breeds prohfically in the stems of Onagra hien- nis and Epilobium. It is liighly parasitized by Neocatolaccus tylodermse, Cerambycobius cyan- iceps, eurytoma ty- LODERMATIS, MiCROBRACON MELLITOR, SiGALPHUS CURCULIONIS, and Urosigalphus sp. no v. GerstsecTceria nohilis LeConte (Acalles). The common pricldy-pear weevil is parasitized by Catolaccus hunteri and by several other species. Fig. 24. — The plum cureuMo (Conotrachelus nenuphar), & cohost of boll-weevil parasites: a, Larva; b, adult; c, pupa. Much enlarged. (From Chittenden.) BIOLOGY OF THE COHOSTS. 79 CEUTORHYNCHIN^. Auleutes tenuipes LeConte. Tliis weevil breeds in the anthers of buds of Galpinsia hartwegi on the Texas black prairie at least. It is attacked by Catolaccus incertus, Microhracon sp., Eutrichosoma alhipes, and possibly by Catolaccus nigrosenea. Crajjonius inxqualis Say. This weevil breeds in the fruit of the grape. It is parasitized by Microbracon mellitor and Stiboscopus hrooksi. Khinoncus pyrrhopus Boheman. Tliis weevil breeds in the stems of Polygonum and is parasitized by Cerambycobius cyaniceps. Ceutorhynchus n. sp. Tliis weevil breeds in the crown of Selenia aurea and is parasitized by Catolaccus incertus. Baris cuneipennis Casey. This weevil breeds in the roots of Helenium tenuifolium and is parasitized by Catolaccus incertus. Orihoris crotchii LeConte. This Lower Sonoran weevil breeds in the seed pods of Mentzelia nuda. It is parasitized veiy higlily by Microhracon nuperus, Eurytoma tylodermatis, and a species of Totrastichus. TricJioharis texana LeConte. Tliis species breeds very abundantly in stems of Solanum rostratum., and is hence more or less a Lower Austral insect. Its parasites are Cerambyco- bius cyaniceps, Eurytoma tyloder- MATis, Microbracon sp., and Sigal- PHUS CURCULIONIS. Trichoharis trinotata Say. The po- tato stalk weevil (fig. 25) breeds in the stems of many Solanacete, includ- ing Solanum. carolinense, S. melongcna (egg plant), 8. rostratum, S. tuberosum (potato), Datura stramonium, D. tatula, Physalis longifolia, P. philadel- pJiica, P. lanceolata, P. Jieteropliylla, and P. virginiana ambigua. It is known to be parasitized by Sigalphus curculionis and Eurytoma TYLODERMATIS. TricTiobaris compacta Casey. This weevil breeds in the pods of Datura stramonium and is also recorded as breeding in Datura mete- loides. It is parasitized by Ceraisibycobius cyaniceps, Myiophasia .aJNEA, and Pediculoides ventricosus. Fig. 25.— The potato-stalk weevil ( Tricho- baris trinotata), a cohost of boll-weevil parasites: o, Beetle; 6, larva from side; c, pupa; d, section of potato stalk opened to show larva and pupa in situ, a, b, c, Five times natural size; d, natural size. (From Chittenden.) 80 INSECT ENEMIES OF THE BOLL, WEEVIL. AmiJeloghipter sesostris LeConte. The grapevine gall weevil is para- sitized by Myiophasia ^nea, Neocatolaccus tylodermse, and Calyptus tibiator. Zygoharis xantlioxyli Pierce. This weevil is abundant in the berries of X antlioxylum clava-lierculis. It is parasitized by Catolaccus HUNTERI and SiGALPHUS CURCULIONIS. BALANININ.E. Balaninus nasicus Say. Tliis weevil breeds in acorns. It is para- sitized by Myiophasia ^nea and possibly by Trichacis rujipes. CALANDRIN^. Cdlandra oryza Linnjeus. The cosmopolitan rice and corn weevil (fig. 26) breeds in acorns of several species of oak, in galls of Phylloxera devastatrix on Hicoria pecan, in old cotton bolls, and in all kinds of stand- ing and stored grain. It is parasitized by Meraporus calandrse, M. vandinei, M. uti- hilis, M. requisitus, and Catolaccus in- CERTUS. Other parasites have been re- ported abroad. 15. A LIST OF THE HOST PLANTS OF THE COHOST WEEVILS. In order to show more plainly the num- ber and variety of plants whose presence around the cotton field, if infested by their typical weevils, would influence the parasite control of the b(dl weevil, the following list is i:>resented, using the classification of Britton (1901): Fig. 26.— The rice weevil ( CWawZro oryza), a cohost of boll-weevil parasites. Enlarged. (From Chittenden.) Plant. Triticiim sativum (wheat) . . Elymus virginicus Zca m.ais (corn) Oryza fatiin (rice) Jiiglans nigra (walnut) Hicoria sp. (hickory) Hicoria alba (hickory) Hicoria pecan (pecan) Quercus spp Phoradendron flavescerv^ Polygomtm penm^ylianicmu rolygonuin portoricense Polygonum punctatum. . . . Ainaranthas retrofiexus. Infested by- Calandra oryza I.. Anthrihufi alternatiLs Say. { Anv cents faf^ciculalus DeG. \ Calandra oryza L. Cahmdra oryza. j, Coiiotrachfliis jvgtandis Lee. Conotrachdus ajjinis Boh. Conotrachelus elegans Say. Conotrachclus elegans. (Balaninus spp. I Conotrachclus naso Lee. [Calandra oryza Ij. Smicravlox tuherculalux Pierce. Lixus viusculus Say. Lixus musculus. Lixus musculus. Rhinoncus pyrrhopns Boh. Conotrachelus elegans Say. HOST PLANTS OF COHOST WEEVILS. 81 Plant. Selenia aurea Rubiis villosus (blackberry) Rubus tiirialis (dewberry) Rubus occidrntalis (raspberry). . . . Fragaria liryiniana (strawberry).. Potentilla canadensis Pyrus communis (pear) Mains malus (apple) Cratsegus mollis (haw) Cratsegus oxyacantha Prumis (plum) Amygdalis persica ( peach ) Amygdaiis persica (nectarine ) Amygdalis armcniaca (apricot ) Vachcllm farnesiana (huisache) . . . Acuan illinoensis Strombocarpris (screw-bean) Prosopis glandulosa (mesctuite). . . Cercis canadensifi (redbud) Cassia obtusifolia Cassia occidcntalis Gleditsia aqyatica (water locust). . . Gleditsia triacanthos (locust) Vigna ungniculata (cowpea) Baptisia bracteata Baptisia leucantha Baptisia tinctoria Amorphafruticosa Indigofera tincforia Cracca virginiana Robinia pseudacacia Vicia sp Meibomia paniculata Phaseolus polystachyus Phaseolus retiisus Phaseolus wrightii Phaseolus vulgaris (bean ) Phaseolus vulgaris Strophostylus pauciflora Xanthoxylum clavn-herculi'i Melia azedarach (China tree) Croton capitatus Croton engelmanni Croton texense Vitis spp. (grape) Callirrhoe digitata Callirrhoe involucrata Sphseralcea angustifolia Gossypiuin Mrsutum (cotton) Mentzelia nuda Opuntia (prickly pear) Opuntia engelmanni Epilobium sp Gaura sp Onagra biennis 16844°— Bull. 100—12 6 Infested by- Ceutorhjnchus sp. Anthonomus siguatus Say. Anthonomus signatus. A ntho no m us signal u s . Anthonomus signatus. Anthonomus signatus. Tachypterellus quadrigibbus Say. Tachy ptcrellus quadrigibbus^. j Tachypterellus quadrigibbus. [Aiithonomus nebulosus Lee. Tachypterellus quadrigibbus Say. Conotrachelus nenuphar Hbst. Conotrachelus nenuphar. Conotrachelus nenuphar. Conotrachelus nenuphar. (Bruchus) Laria salLri Sharp. Laria bisignata Horn. Laria prosopis Lee. Laria prosopis. Anthonomus signatus Say. Arcccerus fasciculat us DeG . Arsecerusfasciculattis. Spermophagus robinix Schon. Spermophagus robinix. Chalcodermus seneus Boh. Tychius sordidus Lee. Tychius sordidus. Apion rostrum Say. Laria exigua Horn. Arxcerus fasciculatus DeG. Apion segnipes Say. Apion nigrum Sm. Laria ochracea Schaeff. Apion decoloratum Sm. Apion griseum, Sm. Apion griseum. Apion griseum. Chrdcodcrmus f^eneus Boh. Laria obtecta Sny. Apion griseum Sm. Zygobaris xanthoxyli Pii'rce. A r^eevil work could 1)0 found, Init on May 7 a single weevil was found after a careful examination of eight fields. On the same date at Six Mile settlement, across the bay near Port Lavaca, there was consider- able infestation. If the parasites hibernated as adults they would be dead long before the middle of June. If they could have hibernated as immature stages they would have matured l>y ]\Iarch 15, and under normal conditions three generations would have passed by June 15. The infestation was still very shght in July. It must be argued, therefore, that any boll-weevil parasites must l)e breeding on some other weevil, if they did not perish. On August 22, 1907, Mr. Mitchell found parasites with weevil- infested squares on a field in the opposite part of the community to that in which he first found the weevil infestation. The obvious inference is that a rotation of hosts occurred during the i)eriod of the boll weevil's absence. Having planned the cropping system, it is also best to prepare the fields early for cotton and plant as early as possible. Of course, most of the reasons for earl}^ planting of cotton are well known and the practice is very common, but in this connection it must be said that such early planting has the actual advantage of enabhng the para- sites to start early. Care must be given to the choice of tlie cotton variety which is to be used. Frequent recommendations have been made of varieties with hglit foliage, early maturing fruit, short nodes, and determinate growth. All of these qualities are favorable to parasite control, 90 INSECT ENEMIES OF THE BOLL WEEVIL. especially since such plants afford much more sunlight on the ground. The ants and also the parasites prefer much more to attack the squares which are dried out than moist squares. It seems that they can more readily penetrate the hnings of the square. In addition to these qualities of the cotton variety, the use of a variety with at least a moderate amount of nectar is also advised. The reason for tliis has been explained in preceding jiaragraphs. Finally, the tend- ency of plants to retain the squares must be again mentioned. If a variety can furnish the desired quahties of early producing, produc- tiveness, and quahty of hnt, as well as a diagonal absciss layer on the square, that variety should be chosen above others. If at all possible, it is advisable to plant the rows far apart or on the check-row system, in order to give the necessary amount of sun- Hght. The cultivations to follow tliis should be with the purpose of obtaining a dust mulch, for with such a mulch the surface of the soil may be heated to a much higher degree than by deep and lumpy cultivation, and the control of the l:)oll weevil will thus be greatly increased, through the drying effect upon fallen squares. 5. now TO PLAN FOR THE GREATEST POSSIBLE CONTROL. As it has been proven that many agricultural processes are favor- able to the development and attack of parasites and enemies, there can be no question but that it is desirable to plan to obtain the great- est amount of this beneficial aid. There are a few plants which have no objectionable quahties in themselves which might with good reason be planted adjacent to the cotton fields in order to induce the attack of weevils which act as hosts of the boll-weevil parasites. For instance, the presence of a hedge of blackberries or dewberries along the fence means the pre- sence of Antlionomus signatus, the blackberry bud weevil, with its numerous parasites, all of wliicli attack the boll weevil. The para- sites would be able to carry on a generation in the spring before the boll weevils were breeding and would mature in plenty of time to attack the first developing stages of the boll weevils. It would seem advisable to plant a hedge of the flowering shrub Amorpha fruticosa, which is the host plant of Laria exigua. This Httle wevil is very abundantly parasitized. In planning the cropping sj^-stem there can be no possible harm in arranging to have a forage or hay crop adjacent to the cotton field. In case a forage crop is used, cowpeas with the ever-present cowpea pod weevil would undoubtedly bring about the presence of several important parasites. The early removal of the cowpeas for fodder would force the parasites to attack the boll weevil. In the case of a hay field, the process of haying and subsequent curing PROPAGATION AND AETIFICIAL INTKODUCTIONS. 91 would enable the parasites present in the various weeds to escape and attack the most abundant host, namely, the boll weevil. If, with all these precautions, the boll weevils are very numerous in the field, and the expense is not too great, much can bo gained by picking the squares and placing them in cages, as has been described in a previous section. Finally, at the proper season for haying, the actual methods of cutting and preparing the hay will without doubt furnish still greater control to the weevil. Some time in Sei)tember, if not before, whether haying is carried on or not, there should be a thorough cutting of all weeds around the cotton field in order to force the parasites to the boll weevil and also to get rid of favorable hibernation quarters for the boll weevil. 6. PROPAGATION AND ARTIFICIAL INTRODUCTIONS. The propagation of parasites under artificial conditions and their introduction are attended with a great amount of labor and expense and have mau}^ technical difficulties. The simplest form of propaga- tion is the collection of infested squares at one locality and the ship- ment of them to another locality, where they are placed in the field to await results. There are good reasons for attempting thus to introduce parasites. It has been found by very close observations that the parasites are not evenly distributed, but that each species has a more or less defimtely defined geographical region. This is no doubt due to the distribution of the normal host weevils. The purposes of introduction are to take these parasites from their native localities and place them in geographical regions in which they do not at present exist. Definite proofs that results can be obtained in this manner were to be had at Dallas on tlie experimental farm in 1906 and also in 1907. The 1906 experiment has been fully described in the first report on the parasites of the boll weevil (Pierce, 1908a). In 1907 a similar experiment was tried l^y the release of large numbers of adult parasites. These parasites were carried to a field in small screen cages containing foliage, so that the parasites might not become overheated. The cages were opened in the shade, and the parasites allowed to fly out in any direction which they pleased. While many species of parasites were released in this manner, they did not all show the results that were expected, but the release of Catolaccus incertus in a given part of the field accomplished an increase in the control in hanging squares by this species. In two other parts of the field Microhracon meUitor was released, and it also showed good gains. As Microhracon was released on this farm both in 1906 and 1907, it may be useful to compare the percentages of parasitism at various periods. In August, 1906, this species furnished 8.5 per cent parasitism in hang- 92 INSECT ENEMIES OF THE BOLL WEEVIL. ing squares; in September, 1906, this had risen to 10.2 per cent; in July, 1907, the parasitism by this species was 35.2 per cent, and in August, 1907, it had risen to 39.8 per cent. At Shreveport, La., in 1908, many specimens of Catolaccus incertus and Microbracon mellitor were released. Table XXII gives an idea of the results and shows the expected increase by Catolaccus in both hanging and fallen squares and by Microbracon in hanging squares. Table XXII. — Experiment in artificial introduction of Catoloccus incertiis and Microbracon mellitor, Shreveport, La., 1908. Plat. Date. Percentage of mortality. Gain in mortality. Class of forms. Total. Para- sites. Cato- laccus. Micro- bracon. Total para- sites. Cato- laccus. Micro- bracon. Fallen squares Release. .. . do Oct. 5 Oct. 28 Oct. .5 Oct. 28 Oct. 6 Oct. 2(1 30.44 37. 90 40. 00 42. 33 47.15 04.80 5.93 15.74 10.50 10. 00 9. 90 37.84 4.23 10.80 5.55 8.00 4.39 10.81 1.70 2.10 3.70 5.00 3.29 18. 91 Per cent. Per cent. Per cent. Do . . 105 1.50 33 Do Check ...do Do 52 44 35 Hanging squares... lielease. . . ...do Do 282 148 477 RELEASE CAGES. In order to obtain satisfactory results from the release of infested material, it is necessary to place the material in cages from which the injurious weevils can not escape but which will still allow the parasites egress. This principle has been exi)lained in other sections. There is also another important consideration in the construction of the cages. When a large amount of material such as this is collected in a small space it furnishes great inducements to attack by colonies of ants. The only way that the material can be protected from total destruction by ants is the isolation of the cage on legs by the use of " inverted cups " containing oil, or by greasing the legs in some manner. TRANSFER OF ANT COLONIES. Since the work of ants is always very favorable to control, means should be devised of increasing their numbers in the cotton field. The dust-mulch method of cultivation is very favorable to the ants in that it does not disturb their colonies after they have commenced breeding. This is a very im})ortant matter to consider. The late Mr. F. C. Pratt, in working with the horn fly {Lyperosia irritans L.) discovered that fresh manure containing numerous fly larvae is very attractive to Solenopsis, and tliat these ants seem to trans- fer their whole colony at times to the manure. Mr. Wilmon Newell, in connection with the Argentine ant investigations, at a later date, found that he could trap immense colonies of the Argentine OBJECTIONABLE PRACTICES. 93 ant {Iridomyrmex Jiumilis) by means of boxes containing manure. These observations are very suggestive, for they point out the possi- bihty that colonies of ants can be obtained by placing fresh manure in boxes near ant colonies. When sufficient numbers have entered, they may be boxed up for removal to a place desired. In tliis manner great colonics could be transferred bodily for considerable distances. 7. OBJECTIONABLE PRACTICES. There are several practices which are quite objectionable from the standpoint of encouraging the ])arasites and most of which have also been found objectionable from purely cultural standpoints. Wlien the cotton is planted closelv on moist soil its growth is mainly vegetative and consequently immense stalks may have very little fruit. Agriculturists have alwa3^s pointed out that large cotton plants need plenty of room in order to produce fruit. Field examina- tions to determins the mortality of the boll weevil from various causes have always shown that the parasitism is greatest in the portions of a field where tlie foliage is lightest. A notable example was found at Natchez, Miss., where in a single field the growth was very irregular. One spot seems to have been used for feeding cattle and was very fertile. On this spot the cotton grew 6 or 8 feet tall and the ground was densely shaded. Here the mortality of the weevil was very low, and there was scarcely any control by insects. One hundred feet from this was a thin piece of ground where the cotton plants were barely 2 feet high, but they were loaded with bolls and showed a much higher percentage of mortality, especially by insect enemies. An actual count of the number of bolls in the two parts of the field was greatly in favor of the smaller plants. Late planting has been proven objectionable from almost every stand])oint from which it has been viewed. Under existing circum- stances there are no valid arguments for late planting. From the standpoint of control by parasites late planting simply delays the attack of parasitic enemies and reduces the amount of control in the fall at a critical time. It is believed that the use of varieties which always tend to drop their squares is objectionable if varieties with the opposite tendency can be found with the same qualities of production. The iwactice of 'picking squares and then burning them can not he condemned too stronghj. The i)lanters are by this practice almost nullifying the good work that they do by picking the squares. They are doing nothing more or less than destroying their best friends when they burn these squares. This may be proven by an hypothesis similar to those presented (p. S7) in demonstrating the value of collect- ing the infested squares. 94 INSECT ENEMIES OF THE BOLL WEEVIL. Given 10,000 developing stages of the boll weevil in a 1 -acre field. (A) Collect and burn squares containing 50 per cent of the stages 5, 000 This destroys all parasites as well as weevils. (B) There remain in the field squares containing 50 per cent of the stages present 5, 000 Normal parasitism 5 per cent 250 Ants and heat kill 40 per cent 2, 000 Mortality 2, 250 Weevils to breed 2, 750 Parasites present in field, 250. There is 1 parasite to every 11 weevils. Tliis method undoubtedly greatly reduces the total number of weevils in the field, but, as can be readily seen, the proportion of parasites to weevils is the same as if nothing had been done — namely, 1 to 11. It was shown that by placing the squares in 16-mesh wire cages the proportion would be 1 to 6.3. Hence it appears that by the caging method the planter leaves in his field a more active agency than he had before to attack the many weevil stages he has undoubt- edly missed, whereas by the burning method he has not in the least improved his field conditions. 8. THE ECONOMIC SIGNIFICANCE OF THE INVESTIGATION. In final summary the following points are emphasized: I. The control of the holl weevil hy insect enemies is sufficiently great to give it a liigh rank in the struggle against the pest. A considerable portion of the insect control would not he accomplished hy any other factor; hence it is hy no means to he neglected. The number of species of insects attacking the developing stages is 49. The control in any given place consists of the combined work of several different species. Places having the largest number of controlling insects have the highest percentage of control. In many places insect control is considerably greater than climatic control or than any other class of factors. The average insect control is 20 per cent of all immature stages or two-fifths of the entire natural control. The cotton leaf-worm is a valuable enemy of the boll weevil when it defoliates the cotton after September 1, a date beyond which new squares can not be expected to mature. It kills many weevils by starvation, kills many others while consuming the squares, and finally forces a premature hibernation which is generally fatal. ECONOMIC SIGNIFICANCE OF INVESTIGATION. 95 II. The amount of control due to the various factors at work in any given place should he increased if possible. Parasites can he introduced into new fields. In order to prevent serious injury to cotton, the mortality of the weevil should be above 90 per cent. It has averaged over 57 per cent for four years and has reached almost 100 per cent several times. "VVliile climatic influences occasionally bring the control above 90 per cent, they can not be regulated or in any way directly utilized. Although the insect enemies present at a given place may be accomplishing the greatest amount of work possible, the fact remains that if other species of enemies are introduced and become estab- lished the control can be increased. Since certain parasites attack the weevil preferably in dry locations and others in wet locations, and since some prefer to attack the infested forms on the plant, while others seek them on the ground, it is possible to select the insect agencies so as to obtain the least amount of lost or duplicated energy. III. The parasites and predators which attack the holl weevil are native insects, already present in a given territory he fore the weevil arrives. The predators, especially ants, will attack almost any kind of insect food. The parasites in nearly all cases are capable of attack- ing almost any kind of weevil breeding in herbs above ground or in fruits. The parasites have proven their ability to adjust themselves to the boll weevil by attacking it in its first generation in newly infested territory in instances where the actual sources of the parasites were demonstrable. The weeds surrounding the cotton fields contain many weevils which are harboring multitudes of available parasites. These para- sites may be induced to attack the boll weevil by the timely elimina- tion of their native hosts. This leads to the recommendation that planters cut the iveeds adjoin- ing the cotton fields, along the roadsides, turn rows, and fences ahout the time of the maturing of the crop. It also leads to the recommendation that a field adjoining the cotton he used as a pasture or hay field, and that this fi.eld he mowed early in the fall. The usual haying will also bring about the same result- namely, the elimination of other plants harboring weevils which attract the parasites needed in the cotton patch. It is advisable to have in the vicinity of the cotton field such plants as the dewberry, Croton, Amorpha, cowpeas, etc., which contain other hosts of the boll-weevil parasites. 96 INSECT ENEMIES OE THE BOLL WEEVIL. IV. The cultural methods of controlling the cotton hall weevil are the most favorable methods of cotton culture from the parasitic standpoint. The tendency of the principal boll-weevil parasites to prefer light and heat leads immediately to a long series of recommendations. Heat on the ground is essential for the climatic control of the weevil and also for parasitic control. Although the two factors overlap, each accomplishes considerable independent control. A heated condition of the ground may he accomplished hy planting the rows far apart, hy check-row planting, hy flat cultivation, or hy planting varieties which have short Umhs, or shed their foliage early, or have small leaves. Fall destruction of the cotton plants cuts off the parasites from breeding on the weevil but sends them to other hosts upon which tliey can breed a winter generation, or pass hibernation, thus gaining not only a generation on the weevil but providing for themselves during the winter. The early planting of cotton in the spring makes it possible for the earliest parasites to attack the weevil. V. The tendency to retain infested fruit, whicli is displayed by certain varieties, is worth consideration. The fact that many more parasites are reared in hanging squares than in fallen squares malies it desirahle in humid regions to have many of the hanging squares in afield in order to serve as a nursery of parasites for the iveevils in the fallen squares. Varieties which show an elongate diagonal connection between the scpiare and stem will tend to have an imperfect absciss layer formed. Prominent in this class are the cluster boll varieties of cotton. It is recommended that search he made for such a variety as will retain its infested forms and at the same time fulfill the other require- inents in the making of a good crop. VI. Any step which will diminish the number of weevils and not diminish the number of parasites in a held will of course increase the percentage of parasites present. The most important step of this kind is the collection of infested squares and placing them in cages loith a screen through which the weevils can not escape hut the parasites can. Ant colonies may be introduced into the fields in boxes of fresh manure. If squares are collected, they should not he hurned, hut should he placed in screened cages. INSECT ENEMIES OF THE BOLL WEEVIL. 97 BIBLIOGRAPHY. Aldrich, John Merton. 1905. Catalogue of North American Diptera.