?,^'/-2X. U. S. DEPARTMENT OF AGRICULTURE, BUREAU OF ENTOMOLOGY— BULLETIN No. 122. L. O. HOWARD, Entomologist and Chief of Bureau. THE ARGENTINE ANT WILMON NEWELL, M. S., T. C. BARBER, B. S. A. Issued June 26, 1913. WASHINGTON: GOVERNMENT PRINTING OFFICE. 1913. Bui. 122, Bureau of Entomology, U. S. Dept. of Agriculture. Plate I. U. S. DEPARTMENT OF AGRICULTURE, BUREAU OF ENTOMOLOGY— BULLETIN No. 122. L. O. HOWARD, Entomologist and Chief of Bureau. THE ARGENTINE ANT BY WILMON NEWELL, M.S., AXD T. C. BARBER, B. S. A. Issued June 26, 1913. WASHINGTON: GOVERNMENT PRINTING OFFICE. 1913. 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. P. 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, in charge of preventing spread of moths, field work. 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, B. R. Coad, G. N. Wolcott, W. A. Thomas, R. W. Moreland, C. E. Hester, engaged in cotton-boll weevil investigations. F. C Bishopp, A. H. Jennings, H. P. Wood, W. V. King, engaged in tick investi- gations. A. C Morgan, G. A. Runner, S. E. Crumb, D. C. Parman, engaged in tobacco insect investigations. T. E. Holloway, E. R. Barber, engaged in sugar cane insect investigations. J. L. Webb, engaged in rice insect investigations. R. A. Cooley, D. L. Van Dine, A. F. Conradi, C. C. Krumbhaar, collaborators. 2 LETTER OF TRANSMITTAL U. S. Department of Agriculture, Bureau of Entomology, TVashingtorij B.C., January 2, 1913. Sir: I have the honor to transmit herewith and to recommend for publication as Bulletin No. 122, of the Bureau of Entomology, a manuscript entitled "The Argentine Ant," by Mr. Wilmon Newell, formerly a collaborator, and Mr. T. C. Barber, formerly an agent of this bureau. The Argentine ant is an imported pest of great importance. It is unique among injurious insects of this country in the diversity of the damage that it causes. It is not only a household pest of the first rank, but it affects materially the interests of sugar planters, orange growers, and others. The territory infested by this ant is being rapidly extended. For all of these reasons it is important that there be placed on record a full account of the studies that have been conducted regarding it. The work upon which this manuscript is based was begun by Mr. Newell as secretary of the Louisiana State Crop Pest Commission. Later Mr. Newell continued the work as a collaborator in this bureau, and Mr. Barber, an agent of the bureau, but working under Mr. Newell' s direction, added to the results obtained. Respectfully, L. O. Howard, Entomologist and Chief of Bureau. Hon. James Wilson, Secretary of Agriculture. CONTENTS Page. Introduction 9 General considerations 10 History and distribution 11 Introduction into Louisiana 12 Present distribution in the Southern States 14 Occurrence and distribution in California 15 Area of ultimate infestation 16 Common name 18 Means of dispersion 19 Natural spread 19 Flight 19 Dispersion by streams 20 Artificial dissemination 20 Economic importance 22 Systematic position 26 Description of the species. 27 Resemblance to other ants 30 Methods of study 32 Establishing colonies for study 36 Life history 38 The egg 38 Period of incubation 39 The larva 40 Duration of the larval stage 41 The pupa 42 The worker pupa 42 The male pupa 43 The queen pupa 44 The callow or teneral stage 45 Time required for complete development 45 The adults 46 The worker 46 Length of life 47 The male 47 The queen 48 The virgin queen 48 The dealated, or fertile, queen 49 The colony as a whole : 51 Seasonal history 51 Winter colonies 51 Summer colonies 52 Compound colonies or communities 54 5 b CONTEXTS. The colony as a whole — Continued. Page Migrations 54 General migration or dispersion 54 Migration to food supply 54 Concentrating migration 5 4 Divisional migration ;,:, Nests or natural formicaries ,",;, Underground nests 56 Wet-weather nests or sheds 56 General observations 57 Aversion to light 57 Sense of smell 57 Sight 57 Hearing 58 Cannibalism 58 Sanitation 59 Rate of travel •. 59 Storage of food GO Relations with other Arthropoda 61 Formicidse <; ] Coccidae and Aphididse 62 List of Coccidae and ApMdid;e attended by the Argentine ant 66 Antagonism toward other insects 66 The Argentine ant and the boll weevil 68 Beneficial aspects of the ant's activities 69 Symbiotic relations 71 Inquilines 72 Natural control 72 Natural enemies 72 Insects and spiders 72 Birds 73 Experiments with Pediculoides 73 Experiments with fungous diseases 75 Low temperatures 76 Floods 76 Methods of repression 7ii Experiments with repellents 78 Corrosive sublimate and ' ' ant tapes " 80 Experiments with fumigants and contact insecticides 81 Experiments with poisons 84 Control of the ant in residences 87 Control of the ant in apiaries 88 Control of the ant in orange groves 91 Method of dissemination in the orange section 93 Experiments in the orange groves 94 Experiments with winter trap boxes 95 Bibliography 97 ILLUSTRATIONS. PLATES. Page. Plate I. Argentine ants upon a tea table Frontispiece. II. A small colony of Argentine ants as seen in one of the artificial for- micaries 32 III. "Formicarium," or special insectary, constructed and equipped for the study of the Argentine ant 36 IV. Immature stages of the Argentine ant 40 V. Wet- weather nest or shed, erected by Argentine ants during rainy weather 56 VI. Orange tree after exposure to Argentine ants for three seasons 64 VII. Beehive on ant-proof hive stand, the latter resting upon a concrete block 88 VIII. Orange orchard dying as a result of infestation by the Argentine ant. 92 IX. Batture of the Mississippi River 50 miles below New Orleans, over- grown with willows and heavily infested by the Argentine ant 92 X. Siphon, pumping plant, and barrier ditch used in limiting the spread of the Argentine ant 92 XI. Bridges which the Argentine ant can not cross 92 XII. Trap box and fumigating cover for destruction of Argentine ant while in winter quarters 96 XIII. Orange grove in which campaign was waged against the Argentine ant — appearance of the grove after recovery 96 TEXT FIGURES. Fig. 1. Map of Alabama, Mississippi, and Louisiana, showing counties in the Southern States which are infested by the Argentine ant 14 2. Distribution of the Argentine ant in California 16 3. Injury to the stand of sugar cane by the sugar-cane mealy-bug (Pseudococcus calceolarise) , which is attended by the Argentine ant.. 24 4. Sugar-cane mealy-bugs on sugar cane 25 5. Covering constructed by the Argentine ant to protect the mealy-bugs. . 26 6. The Argentine ant, adult forms 28 7. Artificial formicary or cage used in studying the Argentine ant 33 8. Artificial formicary with parts assembled ready for use 34 9. Entrance of artificial formicary shown in figures 7 and 8 35 10. Argentine ant removing pupa of sorghum midge from a head of sorghum . 70 11. Ant-proof hive stand, upturned, showing method of construction 90 12. Ant-proof hive stand, sectional view 91 13. Ant-proof hive stand, from above, showing construction 92 7 THE ARGENTINE ANT. INTRODUCTION. The Argentine ant {Iridomyrmex Jiumilis Mayr), which is made the subject of the present paper, is the first among the Formicidae to attain the front rank among injurious insects in the United States. In its field the Argentine ant is not excelled in destructiveness by even the gipsy moth, the boll weevil, or the San Jose scale. Though this ant is limited as yet to comparatively small areas, the observations and experience of the authors fully convince them that future years will see this insect steadily invading new territory and forcing its depre- dations upon the inhabitants of all southern California and most of the Gulf States. The present paper aims to present, in as concise a manner as possi- ble, the principal results of five years of almost constant observa- tion and experiment by the senior author at Baton Rouge, La., and in the orange-growing section of the same State, together with observa- tions made by the junior author at Xew Orleans in connection with his investigations of sugar-cane insects. The junior author has prepared in their entirety the portions deal- ing with the "Area of ultimate infestation," and the " Relation of the ant to Coccidge and Aphididas," and to him is also to be credited the important discovery that mating of the queens may occur within the formicary or nest of the colony. The remainder of the paper, except where otherwise noted, is compiled from the notes and records of the senior author. In the tedious work which accompanied the determination of the ant's life history, from 1907 to 1910, much assistance was rendered by the young men associated with the senior author in the work of the Louisiana State Crop Pest Commission, particularly Messrs. Harper Dean, A. H. Rosenfeld, G. A. Runner, M. S. Dougherty, G. D. Smith, and R. C. Treherne. The writers are under obligations to Dr. W. M. Wheeler, of the Bussey Institution, Harvard University, for permission to use his redescription of Iridomyrmex humilis and for his kindness in reviewing the paragraphs upon " Systematic position" and "Resemblance to other ants." Our thanks are also due to Messrs. R. S. Moore and John Meyer, extensive orange growers of Louisiana, for their liberal cooperation 9 10 THE ARGENTINE ANT. and assistance in experiments carried out in the infested orange districts. GENERAL CONSIDERATIONS. Twenty years ago the Argentine ant was first noticed in New Or- leans, La., by Mr. Edward Foster, reference to whose interesting account of the " Introduction of Iridomyrmex humilis Mayr into New Orleans" will be found on a subsequent page. The species had doubtless been introduced years before that time, but was gathering strength and establishing itself for a considerable period before its numbers became sufficient to attract attention. Mr. Foster men- tions it as occurring in 1891 in "fair numbers." Since then it has increased from a few scattered and apparently insignificant speci- mens to armies and hordes numbering myriads of individuals. It has spread from a few blocks on the water front of the Mississippi River over practically the entire city, and has sent out vast numbers of colonists for hundreds of miles along the railways and waterways radiating from New Orleans. These pioneers have succeeded in founding scores of communities of more or less importance in the smaller cities and towns. Each of these communities is in turn furnishing its quota of migrants, and these are extending the affected territory in all directions from the original source of infestation. Thus, instead of the dispersion being from one source only, it is now taking place from hundreds of different points. From an unknown and little noticed insect this ant has developed into one of the fore- most household pests in the world, and its ravages affect, directly or indirect^, the majority of the crops grown in the South. Former indifference to its movements has given way to concern at its approach, which, in the orange belt at least, means heavy depreciation in the value of property. Continuous study for several years has served to enlighten us on most of the salient features in the life history and economy of the species. A considerable number of poisons and repellents have been tested and have given good results. Methods of isolating, ditching, and winter-trapping have been devised, and have proved their prac- tical value in large experiments under field conditions. Just how much territory this ant will ultimately infest we can not foretell with accuracy from the data at present available. It is quite safe, however, to venture the opinion that the species will eventually spread over a considerable portion of the Southern States — certainly over all of the orange and sugar-cane belts, and perhaps over all of the cotton belt. In California it is likely to cover the territory corresponding in temperature to the belts mentioned for the South, which will include the belts occupied by oranges and other tender fruits. THE ARGENTINE ANT. 11 HISTORY AND DISTRIBUTION. As stated on another page, this species was first described by Dr. Gustav Mayr from specimens collected near Buenos Aires, in Argen- tina. It is also included in the list of Argentine ants by Dr. Carlos Berg. 1 Its occurrence in the Argentine Republic is therefore unques- tioned, and that Argentina is its native home is also borne out by the fact that it does not appear to be generally a pest of importance in that country. Dr. F. Lahille, of the Argentine department of agriculture, in a letter to the senior author, states that it "is uncommon in Buenos Aires and in Argentina generally, where it does not cause annoyance or trouble of value." Mr. Arthur H. Rosenfeld, formerly associated with the writers in entomological work in Louisiana and now located at Tucuman, Argentina, writes that he has been unable to find the species there. Rev. E. Wasmann, S. J., states that this ant "is a native of Brazil and Argentina," and Rev. Albert Biever, S. J., of Loyola College, New Orleans, whose careful studies of this species are mentioned on other pages, has corresponded with various priests in Brazil and Argentina, with the result that he finds that this species is a serious pest in parts of Brazil and evidently in Argentina also. For example, in a letter to Father Biever, Rev. J. Ferol, S. J., of the Colegio del Salvador, Buenos Aires, writes: The ants {Iridomyrmex humilis) of which your reverence makes mention are of no utility whatsoever, but on the contrary are voracious and destructive. Of means employed to destroy them the most effective, according to information given me, is the use of an instrument and ingredient of which inclosed herein I send a prospectus and instructions concerning its use and functions. Forel 2 mentions its occurrence in collections from the States of Sao Paulo and Rio Grande do Sul, in Brazil. Wheeler 3 also mentions its occurrence in that country. Dr. Lahille also states that the Argentine ant occurs in Uruguay and is "especially common in Mercedes and Montevideo," cities not far removed from Buenos Aires. According to Stoll 4 and Wheeler 5 the Argentine ant, after its accidental introduction into the island of Madeira, entirely extermi- nated another ant, Plieidole megacephala Fab., which was itself an introduced species that had exterminated the native ants before it. In 1907 M. N. Martins 6 recorded the occurrence of this ant in Lisbon and Oporto, Portugal, and gave a vivid account of its ravages in those cities and their environs. i Enumeracion sistematica y sinon^mica de los Formicidos Argentinos, Chilenos y Uruguayos. 1890. 2 Ameisen aus Sao Paulo (Brasilien), Paraguay, etc. Verhandlungen der k. k. zool.-bot. Ges. in Wien, 1908. 3 Entomological News, January, 1906, p. 24. 4 Zur Kenntnis der geographischen Verbreitung der Ameisen, Mitth. Schweiz. Ent. Ges., vol. 10, pp. 120-126, 1898. 5 Ants: Their structure, development, and behavior, p. 154, 1910. 6 Une fourmi terrible envahissant l'Europe {Iridomyrmex humilis Mayr). Broteria Revista de Sciencias Naturaes, vol. 6, pt. 1, pp. 101-102, 1907. 12 THE AKGENTINE ANT. In 1908 Prof. C. P. Lounsbury recognized this ant in Cape Town, South Africa, where it had already become a household nuisance and had displayed its usual role of attending mealy-bugs and other insects. The general belief in Cape Town, according to Prof. Lounsbury, was that the pest had been introduced through the medium of forage, large quantities of which were imported from Argentina during the Boer War (1900-1902) and stored in Cape Town. In July, 1910, the late Edwyn C. Reed, of Concepcion, Chile, in a letter to the senior author, reported the occurrence of the species in that country in large numbers. In 1908 ants collected by Mr. J. Chester Bradley, of the University of California, were identified as /. fiumilis by Dr. W. M. Wheeler. Immediately following this discovery Prof. C. W. Woodworth, of the California Agricultural Experiment Station, visited the authors' laboratory at Baton Rouge, La., for the purpose of becoming familiar with the methods used in studying the insect and with the information which had been gathered concerning it up to that time. On his return to California he published a brief circular * concerning its occurrence in that State. From the foregoing it is readily seen that during the past few years this ant has thoroughly established itself, as a nuisance of the first order, on four continents, and, owing to the readiness with which it is disseminated through the ordinary channels of commerce, there seems little reason for supposing that it will not eventually invade all of the semitropical countries of the globe. INTRODUCTION INTO LOUISIANA. As with most imported species, the original time and place at which a foothold was obtained by the Argentine ant in Louisiana must be largely conjectural. However, we are able to conjecture with rather strong circumstantial evidence to guide us. Not only does the tes- timony of inhabitants indicate New Orleans to be the original starting point of this species in the South, but its enormous numbers and the extent to which it has exterminated other species of Formicidae con- firm the opinion that it has been in New Orleans longer than else- where. Mr. Edward Foster, 2 of the editorial staff of the New Orleans Daily Picayune, has given us the earliest record of its occurrence in New Orleans. He noted it in 1891 in St. Charles Avenue, 9 squares from the river and 12 from Canal Street. It was then i The Argentine ant in California. Cal. Agr. Exp. Sta : , Cir. 38, August, 1908. 2 The introduction of Iridomyrmex humilis into New Orleans. Journ. Econ. Ent., vol. 1, No. 5. pp. 289-293, October, 1908. HISTORY AND DISTRIBUTION". 13 present in "fair numbers." At that date it was very scarce in Audubon Park and below Canal Street, but was present in considerable numbers between Magazine Street and the river. "Five or six years later" he found it in St. Peters Avenue, near St. Charles, but it was not abundant. This is about 40 squares north and west from the point on St. Charles Avenue first referred to by Mr. Foster. In a personal letter to the senior author, Mr Foster writes as follows : I have known the species since 1891. At that time it was a rarity in Audubon Park, but was very common in the section immediately above Canal Street. Below Canal Street it was not at all plentiful. The boundary of the nuisance then was virtually from Magazine Street to the river.- The coffee ships from Brazil, I understand, have always landed about where the wharves are now situated (on the river front, adjoining the area above mentioned), but from what we know of the spread of insect nuisances the first batch of immigrants must have come in years before I came across their descendants. Mr. E. S. G. Titus, 1 quoting Mr. E. Baker, former superintendent of Audubon Park, states that in 1896 "they extended over but a small area, reaching approximately from Southport docks to Carrollton Avenue and from the river bank to Poplar Street," and that "in 1899 they were first noticed in Audubon Park." This area, from Southport to Carrollton Avenue, is located about 5 or 6 miles northwest of the area between Magazine Street and the river, noted by Foster to be well infested as early as 1891. Mr. Baker, therefore, had not been familiar with the original area of heavy infestation, but merely noted the species after it had invaded the part of the town where he resided. Mr. Titus's information that the species was first noted in Audubon Park in 1899 was of course secured from citizens, who failed to note the ant until it had reached prodigious numbers in the same place that Foster had found it a "rarity" in 1891. The dissemination to Audubon Park was undoubtedly from the heavily infested area between Magazine Street and the wharves already referred to. The distribution of the species in 1904, as given by Mr. Titus, 2 was as follows : Across the river in Algiers and adjoining small settlements; at West End, Spanish Fort, and Milneburg, summer resorts on Lake Ponchartrain; Bay St. Louis, Miss., a summer resort between New Orleans and Mobile; along the Texas & Pacific Rail- road at Donaldson ville, Cheney ville, and Alexandria; along the Southern Pacific at Thibodeaux, Schriever, Houma, Berwick, Morgan City, Franklin, New Iberia, and La Fayette, and at Opelousas. There is every reason for supposing that this ant was introduced into New Orleans by means of the coffee ships which have for years » Bui. 52, Bur. Ent., U. S. Dept. Agr., p. 79, 1905. 2 Ibid., p. 82. 14 THE ARGENTINE A XT. passed back and foTth between that city and Brazilian ports. This view is supported by the fact that large numbers of the ants were first noticed in the vicinity of the wharves where these ships unloaded their cargoes and also by the fact that these ships have been the only means of regular communication between Xew Orleans and the countries in which the ant is indigenous. That this and other species of ants are actually transported on ocean-going vessels has been fre- quently observed. Thus in July, 1911, the senior author, while a passenger on one of the largest coastwise vessels between New Or- leans and Xew York, found colonies of this same ant occupying pro- tected situations in the woodwork of the steamer. Dr. W. M. "Wheeler also writes us that while returning from Guatemala aboard a fruit Fig. 1.— Map of Alabama, Mississippi, and Louisiana, showing counties in the Southern States which are infested by the Argentine ant, according to the authors' records. (Original.) steamer in January, 1912, he found it infested with another common ant, Prenolepis longicornis Fab. PRESENT DISTRIBUTION IN THE SOUTHERN STATES. The area in the Southern States within which the Argentine ant is known to occur at present extends from Montgomery, Ala., to Lake Charles, La., a distance of about 380 miles east and west; and from Delta, La., to the mouth of the Mississippi River, a distance of about 250 miles north and south. (See fig. 1.) This section is not uniformly infested, but contains a great number of infested areas of more or less importance, ranging in size from many square miles of HISTORY AND DISTRIBUTION. 15 occupied territory, as illustrated by the infestation at New Orleans, to areas where the ants are so scarce that one not accustomed to their habits would fail to discover them. The latter condition prevails at present in Mobile, Ala. The only places remote from railroads where they have been discovered are upon the banks of the Missis- sippi River below infested localities. Their presence in such loca- tions is easily accounted for by supposing that they have been carried thither on driftwood, which, carrying numbers of ants from infested places farther up the stream, has become stranded on the river banks, thus establishing new foci. In all other cases the infested territory is on a railroad, and usually on a main line running out from New Orleans. For example, nearly every town along the Southern Pa- cific Railway between New Orleans and Lake Charles is infested, and the same statement applies to points on the Louisville & Nashville Railroad between New Orleans and Mobile. OCCURRENCE AND DISTRIBUTION IN CALIFORNIA. The first specimens of the Argentine ant observed in California were collected in 1907 by Mr. J. Chester Bradley, at that time an assistant in the entomological department of the University of Cal- ifornia. The identity of the specimens was not established until 1908, when Dr. W. M. "Wheeler found them to be Iridomyrmex Jiumilis Mayr. As soon as the dangerous nature of the pest was known, Prof. C. W. Woodworth took steps to make a study of the species along the same lines as was being conducted in Louisiana at that time, and as a result of his preliminary work he issued a warning circular x to the public in August, 1908. In this circular he gave a brief outline of the habits of the ant and reported the following localities as infested: In the central portion of the State, East Oakland, Alameda, San Francisco, San Jose, Cupertino, and a point near Campbell; in the southern part of the State, Los Angeles, Azusa, and Upland. In 1910 Prof. Woodworth published another small bulletin 2 giving the results of his two years' study of the insect. In this paper the infested territory was more clearly defined, and was estimated as consisting of a total area of 5,000 acres. About twice the area was reported infested in 1910 as in 1908, owing to the discovery of a few new colonies and the natural spread of the ones first discovered. Our information as to the extent of the infested area in California (see fig. 2) has been obtained principally through the kind offices of Mr. Ralph Benton, of the California Agricultural Experiment Station, and Mr. P. E. Smith, of Santa Paula, Cal., as well as from the publi- i The Argentine ant in California. Cal. Exp. Sta. Cir. 38, Berkeley, Cal., August, 1908. 2 The control of the Argentine ant. Cal. Exp. Sta. Bui. 207, Berkeley, Cal., October, 1910. 16 THE ARGENTINE ANT. cations by Prof. C. W. Woodworth, already referred to. All of these persons agree that the following California points are infested: Ala- meda, Azusa, Berkeley, Byron Hot Springs, Campbell, College Park, Cupertino, Fruitvale, Los Angeles, Melrose, Oakland, Riverside, San Francisco, San Jose, Stockton, and Upland. 2 ILo m / r<"»»i» slKSj rmnn V-*- Sir :a\ T E H4^ R^ -:•/ L A 6 S E N €2 B^r ! .;v\ ! ^C §P <*>¥, £.V x*o !\ as u& m*wm > •■■-.-■•***'-,'?•■■.■ r V c-o /, E^-*^ £x ■r^ --