/ / 
 
 1 
 
 1'. S. DEPARTMEN1 OF AGRICULTURE, 
 
 BUREAU OF BHT0M0L0GY- CIRCULAR No. 172. 
 
 I < > I IOWARI >. I nlomolojri.l «nd Oriel ol IW.u. 
 
 INK RKI> si'IDKI! ox COTTON 
 
 e. \ McGregor, 
 
 Entomolonii n\ 
 
 
 
BUREAU OF ENTOMOLOGY. 
 
 L. O. Howard. Entomologist and Chief of Bureau. 
 
 C. L. Mari.att, Entomologist and Acting chief in Absence of Chief. 
 
 R. S. Clifton. Executive Assistant. 
 
 W. F. Tastkt, Chief Clerk. 
 
 F. H. Chittenden, in charge of truck crop and stored product insect investigation t. 
 
 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 <in<t forage insect investigations. 
 
 A. L. Qttaintance, iu 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 icork. 
 
 Mabel Colcord, in ehanje of library. 
 
 Southern Field Crop Insect Investigations. 
 W. D. Hunter, in charge. 
 
 W. D. Pierce, G. D. Smith, J. I). Mitchell, Harry Pinkus, B. R, Goad, R \V. 
 
 Moreland, A. W. J. Pomerov, engaged in CO I ton-boll weevil i n rest if/a t ions. 
 
 F. C. Bishopp, A. H. Jennings, H. P. Wood. W. V. King, engaged in tick life- 
 history in vestigations. 
 
 A. C. Morgan, G. A. Runner, S. E. Crumb, D. C. Pabman, engaged in tobacco 
 
 insect in vestigations. 
 T. E. Holloway, E. R. Barber, engaged in sugar-cane insect investigations. 
 
 E. A. McGregor, W. A. Thomas, engaged in red spider and other cotton insect 
 investigations. 
 
 J. L. Webb, engaged in rice insect investigations. 
 R. A. Cooley, D. L. Van Dine, A. F. Conradi, collaborators. 
 ii 
 
 ADDITIONAL COPIES of this publication 
 -ii- may be procured from the Superintend- 
 ent of Documents, Government Printing 
 Office, Washington, D. C, at 5 cents per copy 
 
Circular No. 172. taoedMaj 11 
 
 United States Department of Agriculture, 
 
 BUREAU OF ENTOMOLOGY 
 L. O. HOWARD, Entomologist and Chief of Bureau. 
 
 THE BED 8PIDEB ON COTTON. 1 
 
 [Tetranychua bimaculatus Harvey.) 
 
 By K. A. Mi(i nil, 
 
 Entomological issittant. 
 
 [NTHOD1 < TION. 
 
 The minute reddish mite commonly know n as the red spider appar- 
 ently i- becoming one of the serious enemies of the cotton planl in 
 
 the United State-. It i- now prevalent throughout the cotton licit, 
 and. especially in the last few seasons, has caused much alarm among 
 the fanner- in certain sections. Seasons of excessive drought arc 
 favorable to the development of the mite, and at such time- the pest 
 increases 90 rapidly that the damage often becomes severe before it- 
 presence i- detected. 
 
 Red-spider infestation i< frequently miscalled "rust*' by farmers, 
 since infested leaves soon turn deep red on their upper surface. Such 
 leave-, however, if examined underneath, reveal the presence of the 
 red spiders and the inconspicuous webs behind which they arc feed- 
 ing and laying their eggs. 
 
 HISTORY \M> DISTRIBUTION. 
 
 With the exception of an outbreak in Louisiana, reported by Prof. 
 II. A. Morgan in L893, severe occurrence of the red spider on cotton 
 had not been rep. rted until 1903, at which time complaint- of dam- 
 age came from South Carolina and Georgia. In 1904 Mr. I-'.. S. G 
 
 1 This firruinr i* baaed primarily upon work done :it Batesburg, s C, in 1911 and 1912, 
 under rh.> direction of Mr. W. l» Banter, bat also Include* the results o( uuaenal 
 
 <;. a. Runner and 11 f. Wilson daring the two preceding seasons, it - 
 »f and ■opersedes Circular No. !■"". 
 
 1 
 
THE RED SPIDER OX COTTON. 
 
 Tit id-, then of this bureau, found severe infestation in fields about 
 Batesburg, S. C, and the following year he reported severe injury 
 in North Carolina. South Carolina. Georgia, and Alabama. Since 
 then the additional records of Dr. F. II. Chittenden and Messrs. 
 G. P. Weldon, D. T. Fullaway, and others, as well as the writer. 
 have established the presence of this red spider from Maine to Flor- 
 ida and westward to California and in the Hawaiian Islands. With 
 the exception of western Colorado and portion- of California no 
 complaints of an alarming nature regarding this pest have come to 
 
 the writer's attention other than from 
 the southeastern portion of the cotton 
 belt. It is here that the red spider ap- 
 pears to have found the conditions most 
 suitable for its development. 
 
 The red spider was described by Har- 
 vey in 1893 as Tetranychua 2-maculatu8. 
 Harvey considered it quite distinct from 
 the European species T. telarius L. His 
 types were from Orono. Me. In 11)07 
 Prof. H. A. Morgan published observa- 
 tions on the cotton mite, and apparently 
 accepted the determination of the species 
 as T. telarius. In 1D00 Mr. Nathan Banks 
 described the cotton mite under a dis- 
 tinct name — Tetranychua gloveri — but 
 from the study of additional specimens 
 has now concluded that the name is 
 synonymous with Harvey's T. bimacu- 
 latus. Specimens of red spiders on cotton 
 from South Carolina have upon two re- 
 cent occasions been determined by Prof. 
 A. Berlese as the continental specie: — 
 Tetranychua telarius. As there seems to 
 be considerable doubt on this point, we shall follow Mr. Banks 
 in considering the form with which we are dealing as Tetranychua 
 bimaculatus. 
 
 DESCRIPTION. 
 
 The typical female (fig. 1) is 0.50 mm. long by 0.26 mm. wide. 
 broad-oval, widest in front, and the legs are shorter than the body. 
 Its color is usually brick-red. The typical male is 0.27 nun. long by 
 0.1.") mm. wide, oval-wedge shape, narrowed behind, the legs about 
 equaling the length of the body, and its color i- usually reddish 
 amber. Individuals of both sexes usually possess on either side of 
 the body a dark spot, caused by the food contents. This -pot may 
 vary greatly in color, size, and outline. Similarly, depending upon 
 
 Fig. i. The red spider, Tetrany- 
 rlnis Mmaculatus: Adult fe- 
 male G r e a t 1 y enlarged. 
 i From Banks, i 
 
I ill i;i D BFIDI R ON COTTON. •'. 
 
 the host plunl and upon locality, the general color of the red spider 
 i- subject i o great * ariat ion. 
 
 I'lu' egg are ven minul ■. but in proportion to the mites the} are 
 large. 1 1 n- \ are perfectly round, and when first laid are as cleai i 
 water. Bach female lays (in the months of June, July, and August) 
 
 about .'in to 60 eggs, although her br I may in cases exceed 100, 
 
 [Tsualh about G i^^- are deposited \»y da} for a period of fl or 10 
 days. Less than •'• eggs or more than I" are rarely deposited in one 
 day in summer weather. During the warmer months the eggs hatch 
 in about I daj - a fter being laid. 
 
 The newly hatched red spider, called the larva, is almost round, 
 has six legs, and is nearh colorless. Ii begins feeding at once, and 
 i in summer time) after two days 1 activity it becomes quiet, darkens 
 in color, casts its skin for the first time, and emerges as the primary 
 nymph \\ ith an added pair of legs making eight. 
 
 The primary nymph becomes larger in size and darker in color, 
 I ii it gives no indication of sex. Feeding continues actively, and at the 
 termination of another two-day period i in summer months) :• second 
 molting occurs, which gives rise to the third stage the secondary 
 nymph. 
 
 With this last nymphal stage the first indication of sex appears. 
 As with the preceding stages, two days usually suffice in summer 
 for the completion of this period, at the end of which time the 
 skin is shed for the third time and at last the perfectly developed 
 
 adult mill'- appear. Ai il :currence of each molt the skin splits in 
 
 two, crosswise, and tin- creature crawls out of the two halves. The 
 old cast skins are usually t<> be seen in abundance among the fibrils 
 of the \\ eb. 
 
 I III \DI M \I \I l - \\n FEMALES COMPARED. 
 
 Concerning the relative abundance of females and males it may !>»■ 
 said that there seems to be n predominance of females throughout 
 the summer, but toward the approach of cold weather the occurrence 
 of the sexes becomes more nearly equal. The period of life of the 
 .•idult female varies from 1" tiny- in midsummer to several months 
 in winter. The male is shorter lived. A- before stated, the female 
 i- decidedly larger than the male, more rounded behind, and of a 
 much deeper color. She does n< >t move about much, and when she 
 ■ loo- her motion is rut I in- slow. < hi the other hand, when not mating, 
 the male is frequently seen moving rapidly about. The body and 
 legs are well beset with bristles, which are -"mew hat more con 
 spicuous in the male- than in the females. In addition, the legs of 
 the male are longer in proportion to the body than are those of the 
 female. The legs of the first pair are especially long in the male, and 
 are doubtless adapted for clasping. The ey< -. consisting ea< h of two 
 orbs, one close behind the other, are situated near the front edge of 
 the body directly over the second pair of legs. 
 
THE RED SPIDER ON COTTON. 
 
 MATIXO. 
 
 Almost immediately upon becoming adult, the red spiders mate 
 and begin egg laying. The males seem to recognize unfertilized 
 females with ease. The first eggs are frequently deposited on the 
 same day upon which the transformation occurs from the last 
 nymphal to the adult stage. 
 
 PARTHENOGENESIS. 
 
 Experiments conducted with unmated female red spiders clearly 
 prove that they are normally capable of laying eggs, which in turn 
 hatch and develop into mature individuals. Xo tests, however, have 
 been successfully conducted to determine the sexual fertility of the 
 latter. 
 
 GENERATIONS. 
 
 The season of 1911 at Batesburg, S. C, was one of unusual drought 
 and heat, and there were about IT generations between March 11 and 
 November 5. The time required for a single generation varied from 
 35 days in March and early April to 10 days throughout most of 
 .Tune, July, and August, and to 25 days in the greater portion of 
 October and early November. During the same period of 1912 at 
 Batesburg only 1G generations were produced. The 1912 season 
 was late in commencing, was somewhat cooler than that of 1911, and 
 more showers occurred. From April 24 to September 25 there was 
 small variation in the time required for the generations — averaging 
 about 11 days. Two generations developed each in 9 days, which is 
 less than was required for any brood in 1911. Thirty days was re- 
 quired for the October-November generation. The following table 
 presents the duration of each stage of each of the 17 generations 
 for 1911 : 
 
 Table I. — Development of veneration* of tin- nil spider on cotton in 1911. 
 
 Gener- 
 ation. 
 
 Period covered by generation. 
 
 Incuba- 
 tion 
 period. 
 
 Larval 
 period. 
 
 Nvmph 
 
 "(1) 
 period. 
 
 Days. 
 
 Days. 
 
 Days. 
 
 13 
 
 9 
 
 6 
 
 6 
 
 3 
 
 3 
 
 6 
 
 3 
 
 3 
 
 5 
 
 3 
 
 2 
 
 5 
 
 3 
 
 2 
 
 4.5 
 
 2.5 
 
 2 
 
 4 
 
 2 
 
 2 
 
 4 
 
 •> 
 
 2 
 
 4 
 
 2.5 
 
 2.5 
 
 4 
 
 2 
 
 2 
 
 4 
 
 2 
 
 2 
 
 4 
 
 2 
 
 ) 
 
 5 
 
 2.5 
 
 ■> 
 
 5 
 
 2 
 
 2 
 
 5 
 
 3.5 
 
 3 
 
 >; 
 
 A 
 
 A 
 
 9 
 
 6 
 
 5 
 
 5.5 
 
 3.1 
 
 2.7 
 
 Xymph Ovipo- 
 i2i sit ion to 
 period. adult. 
 
 1 
 2 
 3 
 4 
 5 
 6 
 7 
 8 
 9 
 10 
 11 
 12 
 13 
 14 
 15 
 16 
 17 
 
 Mar. 11 to Apr. 14. 
 Apr. 15 to Apr. 29. 
 Apr. 30 to Mav 13. 
 Mav 11 to May.'.",.. 
 May 26 to June 6.. 
 June 7 to June 17.. 
 June is to June 27. 
 June 28 to July 7.. 
 July 8 to July 18.. 
 July 19 to July 28. 
 July 29 to Auj;. 7.. 
 lug. B lo Aug. 1 , .. 
 Aug. is to Aug. 29. 
 A.ug.30toSept.9. 
 Sept. 10 to Sept. 24 
 Sept. 25 to Oct. io. 
 
 Oct. 11 to Nov. 4.. 
 \verage 
 
 Days. 
 
 2 
 
 2 
 
 2 
 
 2 
 
 2 
 
 2 
 
 2 
 
 2 
 
 2 
 
 2.5 
 
 2 
 
 3. a 
 
 4 
 
 5 
 
 Days. 
 
 35 
 15 
 14 
 12 
 12 
 11 
 10 
 10 
 11 
 10 
 10 
 10 
 12 
 11 
 15 
 16 
 26 
 
 2.8 
 
I ii I Kin BPID1 i: ON ' 01 l<>\". 5 
 
 le 1 1 indicates the duration of, and the period covered by, each 
 of tlir it, generations for 1912 ;i- well at for the 1911 12 wintering 
 era I ion. 
 
 I.I || / I, l i h, /il, 1 1 ill ,,! : il' Hi l H I I'm - .■• ./hWi , .,</ i nl Inn in I''! ' 
 
 
 M 
 
 ia 
 ta 
 
 ii 
 ii 
 i a 
 i-' 
 ii 
 
 
 Hon 
 
 \n 1 191] to \ 
 
 
 
 \i>r 
 
 
 in 
 
 ■ 
 
 
 
 
 
 
 10 
 
 
 i 
 
 ia 
 
 
 
 17 
 
 
 ■ 
 
 
 1 to Jill \ 1 1 
 
 
 
 Jul' IS to Jul \ .'I 
 
 
 
 
 
 
 ■ * Intering nil itaoold I 
 
 km \iin\ OP w I v 1 ill 1 : I" BREEDING \' ITVITIES. 
 
 The influence of the weather on breeding activity is ven notice- 
 able. Hot, dry conditions greatlj favor and hasten development, 
 while cool, wet weather correspondingly retards it. A female laying 
 normally about 6 or 7 eggs per day will often upon the occurrence 
 of .i very hoi day suddenly increase the number to 15 or even more 
 eggs per day, or upon a chilly day may drop ;i- suddenly to 1 or -1 
 Ii i> easy then to understand the remarkable rate al which 
 this pest increases during times of unusual drought. 
 
 OBSERVATIONS on HABITS. 
 
 Iii establishing herself upon cotton the female selects a concave 
 area between the under veins of the leaf and begins ;it once to deposil 
 eggs. These may be attached to the fibrils of the web slightly above 
 ilic surface, or, as seems mosl often the case, they are placed directly 
 upon the leaf. The eggs are usually clustered rather closely and 
 rarely occupy an area greater in size than that of a dime. Feeding 
 continues interruptedly throughout the period of egg laying, and the 
 affected area of the leaf becomes thickly dotted with the blackish- 
 green puncture marks. Meanwhile ;i wine-red spol has appeared on 
 the upper surface of the leaf directly over the young colony, which 
 spreads ;i- the colony increases and may finally color the entire leaf. 
 A> the eggs hatch the larva? remain close to the place of their birth. 
 The mites seem to U- decidedlj gregarious. In n young colony 
 there is usually little web formed, bul where the spiders are veri 
 abundant the web may become quite conspicuous. It doubtless 
 affords some protection from adverse weather conditions, as well ib 
 .i ir:i : n-t hostile intruder-, since upon several occasions predaceous 
 
THE RED SPIDER ON COTTON. 
 
 insects have been observed ensnared and dead among the fibers. New 
 females, after mating, either select an attractive --pot on the leaf, 
 or migrate upward to a more tempting leaf, or, as frequently is the 
 case when overcrowded, travel to another plant. 
 
 THE VIOLET AND POKEWEED AS HOSTS. 
 
 When cotton dies or becomes un tempting in the late fall an exodus 
 of red spiders from the cotton fields occur- in the effort to find more 
 suitable food plants. At this time cotton mites may be easily found 
 on a number of native and cultivated plant-, prominent among which 
 are cowpeas, tomato. Jamestown weed, ironweed, pokeweed, and cul- 
 tivated violets. Most of these plant- die after the frosts, but poke- 
 weed furnishes considerable green tissue beneath the ground level. 
 
 and the violet remains somewhat green 
 throughout the winter. Out of many 
 case- of cotton infestation investigated 
 during tin- last two seasons the rast 
 majority of them have indicated 
 most clearly that the original source 
 of the pest was either the English 
 violet (figs. •_'. 3) or pokeweed [Phyto- 
 lacca <1( candra) (fi<r. 4). 
 
 Practically all occurrences in urban 
 localities have been intimately associ- 
 ated with cultivated violet plants and 
 doubtless originated from them. On the 
 other hand, with very few exceptions 
 rural case- of infestation are traceable 
 to pokeweed -talks growing at the 
 field borders or on the terraces. The 
 description of a rural occurrence at 
 Allendale. S. C. will serve to illustrate a typical case of origin from 
 pokeweed. In this instance the infestation was seen to grow increas- 
 ingly severe as one approached a certain point on a terrace. Con- 
 verging from all directions toward this center, infestation clearly 
 became heavier until an area was reached where the plants were de- 
 nuded of foliage. Precisely in the center of this area there grew a 
 large pokeweed stalk. It was "alive" with mites and was lightly 
 festooned with their webbing. 
 
 It is not yet entirely clear in what maimer the red spider passes 
 the winter on pokeweed. The plant i- a perennial, and the stalk- die 
 to the ground in the late fall. Just below the soil surface, however, 
 the soft fleshy roots, which are succulent, begin (fig. 4). In addition, 
 at the crown of the root, at about the ground level, there are always 
 
 
 : : -i-V: ':■■;■':: 
 
 
 
 o O O 
 
 
 
 o 
 
 
 
 o 
 
 
 
 • □ 
 
 
 Fig. 2. — Diagram showing how vio- 
 lets growing in dooryard give 
 rise to red-spider infestation in 
 adjoining field. The infestation 
 is most severe near tli" yard. 
 This diagram is typical of many 
 cases found during 1011. (Au- 
 thor's illustration, i 
 
I 11 I. Ill l> -. I • 1 1 • i I: i'\ COTTON. 
 
 to be found through the winter months the tender dormant bud.s 
 which give rise t<> the stalks of the following season. Upon Novem- 
 ber 23, 1912, following -«-\ **t;i I severe fro ts al Batesburg, S I 
 few uf the mites were seen, apparently feeding on these winter buds. 
 
 mi in i; 1 1 « • — i — . 
 
 A- a result of the investigations at Batesburg. together with tin' 
 earlier observations <>l the red spider mi cotton, tlii- mite has been 
 seen upon over 90 species of plants, including weeds, ornamental 
 plant-, ami garden and field crops. Upon most of these the pest has 
 ,inlv occasionallv been seen, '"it it has been found commonlv through- 
 
 ■ pica I * lolel bo 
 plants constituted the son m which resulted In the - in of a 
 
 mall i > otton Beld direct I j a< r — the • 
 
 out the active season upon the following plant-: Beans, cowpeas, 
 dahlia, ironweed, Jerusalem-oak weed. Jamestown weed, okra, tomato, 
 wild blackberry, wild geranium, pokeweed, and English violet. \1 
 Brownsville, S. ('.. Augusl s . I'.M-j. a case was seen where a field of 
 corn was immediately adjacenl to a badly infested cotton patch. The 
 infestation had spread into the corn and the cowpeas growing be- 
 tween the corn rows. One-fourth of the corn had been pulled up 
 ami the balance was very severely infested. Many of the cornstalks 
 exhibited large rusty-yellow blotches on their blades and, in fact, 
 had the pesl appeared when the corn was younger it probably would 
 have ruined the <rop. On the cowpeas the infestation was heavy. 
 many of the leave- had dropped, and those remaining were discolored 
 and distorted, 
 
 78463 Or. 172 18 2 
 
THE RED SPIDER ON COTTON. 
 HIBERNATION VERSrS WINTERING 
 
 Some observers have thought that the red spider commonly hiber- 
 nates in trash or in the soil in cotton fields, but the investigations in 
 South Carolina have produced absolutely no evidence to support this 
 idea. During the late fal] and early spring, when the weather was 
 
 Pig. i System of Besby roots of the pokeweed (Phytolacca decandra), showing the 
 attractive winter buds at about the ground level, ;is indicated by the dotted line. 
 i Original, i 
 
 as cold as it becomes in South Carolina, trash has been taken several 
 times from fields in which the infestation had previously been severe 
 and examined with great care. A few minute dormant acarids and 
 other forms have thus been obtained, but no red spiders have been 
 
 found in such material. 
 
Ill I. i;i I' SPIDI H ON COTTON. 
 
 
 Thai ilii> pesl remains more or less active throughout the winter 
 
 there can be loubt. Mr. <> \. Runner f< I active adults al 
 
 Batesburg, S. C, <>n December 21, 1909. Mr. II. I . Wilson observed 
 red spiders feeding In earlj February :ii the same locality, rhe writei 
 found ;ill stages alive on English violets on March LI, and adults 
 late as December L9 al Batesburg on the same host in 1911. Adults 
 were seen alive on violets al Batesburg on February 23, 1912. follow 
 Ins the coldesl winter thai section had experienced for mam years. 
 
 
 
 V. 1 
 
 \* 5:1 
 
 f^r w 
 
 
 
 ■ 
 
 An uninfested cotton plant, - Id as shown In I 
 
 beyond the boundnrj of Infestation bj the red Bplder. 
 
 The finding of the active red spiders during the coldesl weather is 
 certainly an additional indication thai hibernation does nol take place 
 in South Carolina. 
 
 DISPI RSIOX. 
 
 How do red spiders become established upon cotton? They have 
 no wings and theii legs are very minute. Cloa observations n 
 that on the ground they normally travel at the rate of 1 inch per 
 L5 seconds, which, it' maintained, would total -l v|1 feel in 24 hour-. 
 Red spiders are doubtless occasionally transferred by dogs, chickens, 
 
10 THE BED BPIDEB ON COTTON. 
 
 other domestic animals, insects, and bird-. Strong winds may serve 
 occasionally to transfer them from plant to plant. It i- the writer's 
 firm belief, however, that the chief means of dispersion is the red 
 spider's own efforts. When once established in a field they may be 
 further distributed by farm hands and by stork while cultivation is 
 being carried on. They also spread from plant to plant along the 
 interlacing branches, but trap- specially prepared with tanglefoot 
 and placed in the Held have proven that individuals commonly crawl 
 from plant to plant by way of the stalk and the ground. 
 
 Since the red spider apparently uses no instinct or intelligence in 
 finding cotton plants, it follows that the pest must hit upon the cotton 
 stalk- entirely by chance. The result of this haphazard manner of 
 migration must necessarily result often in the penetration of the 
 spiders far into the center of fields, thus giving rise to the mistaken 
 impression that they had hibernated at these point-. 
 
 Furthermore, as the likelihood of the discovery of cotton by the 
 spider is doubtless in proportion to the thickness of the " stand." it 
 should follow that the thick broadcasting of a narrow border strip 
 along the edge of a field adjoining a source of infestation would serve 
 as a trap crop to intercept the majority of migrating spiders. This 
 strip should be plowed in as soon as there seems to be danger of a 
 general movement to the main field. (For a practical test of this idea, 
 see under Prevention, p. 17.) 
 
 There is an old adage which has come to the writer's attention 
 several times the past season from the lips of old planters: "When 
 the pokeweed turns red, look out for the cotton ' rust." ' This ex- 
 pression, said to have been employed in antebellum days, is of con- 
 siderable interest, since it contributes evidence tending to prove the 
 long existence of the cotton mite in the South, as well as the function 
 of the pokeweed. 
 
 TIME OF APPEARANCE AND DISAPPEARANCE. 
 
 In 1911 the work of the pest on cotton first became noticeable about 
 June 1 at Batesburg. The past season (1912), however, red-spider 
 work was not evident on cotton until about the last of June at that 
 locality. From the answers to a large number of inquiries sent to 
 fanners throughout South Carolina, the average time of first appear- 
 ance in fields the past season is found to have been June 30. The lower 
 (sandy) section of the State averages one-half month earlier in the 
 pest's arrival than does the upper (clay) section — June 2."> marking 
 the arrival time for the former and July 10 for the latter. Although 
 the pest does not become readily noticeable on cotton until some time 
 in June, it really establishes itself considerably earlier. Mites have 
 •asionally been seen by the 1st of May on seedling plants not over 
 
Ill I 1:1 i' -I'lhl i; ON COTTON. 
 
 11 
 
 '_' inches high. In both l'-'ll and 191j2 the pesl abandoned cotton 
 about the Insl of August. This makes the period of activity cover 
 
 :i I >< ii 1 1 12 w ceks. 
 
 \ \ n 1:1 • .1 |p \ M m.i . 
 
 The presence of the pest <>ii cotton is first revealed by the appear 
 a nee on the upper surface of the leaf of a blood red spot. A- leaves' 
 liecome l>adl\ infested ihe\ redden over tin* entire surface, become 
 
 ,i. Cross section of normal cotton leaf; <>. cross section ol cotton leal Injured 
 tii.- red spider. The puncture Is near lower right-hand corner. Highly magnified 
 i tatbor'a Illustration I 
 
 distorted, and drop. Figure 5 shows an uninfested cotton plant for 
 comparison with figure 7. infested. The lower have- usually are first 
 attacked, but infestation spreads upward until often only the bare 
 stalk and one or two terminal leaves remain, i Sir fig. s . i Such 
 plants almost invariably die. The injury to the leaf and the dis- 
 coloration which follows the feeding of the mites are easily under- 
 stood by referring to figure 6, winch represents (a) the appearance 
 of healthy cotton leaf : tissues and (6) the condition of the tissue 
 after feeding by the pest. As previously intimated, the worst spots 
 of infestation arc cither to be found in close proximity to yards with 
 Ixtrders of violets or to a clump of pokeweed stalks. Large fields are 
 probably never completely damaged, bul -mailer fields frequently 
 become wholly affected. A thorough examination of all fields within 
 1 mile of the center of Leesville. S. C, was made with a view of detei 
 mining the exact status of red-spider infestation at one specif] • 
 
12 
 
 THE HED SPIDEB <>N COTTON. 
 
 locality. In all, 99 fields were examined as carefully as possible. 
 The following table presents the result.-: 
 
 Table III. — Results of mi investigation to determine th< degree of infestation of 
 cotton by the red spider at Leesville, 8. <'.. 1912. 
 
 Number 
 Degree of infestal Ion ol fields ex- 
 amined. 
 
 Per cent 
 of total 
 fields ex- 
 amined. 
 
 Very acute i x 
 
 Very considerable 20 
 
 Slight 35 
 
 None 26 
 
 is 2 
 ■l- 1. 2 
 35. 3 
 26 3 
 
 Total 99 
 
 100.0 
 
 
 Total number of fields visited 
 
 Total number of fields infested " : * 
 
 Average percentage of infestation for the community \.'i 
 
 In;. 7. — Cotton plant in an early stage "f 
 infestation by the red spider. Many leaves 
 are discolored and some of the lower ones 
 have dropped, i Original. I 
 
 p 1G s. — Cotton plant in well ad- 
 vanced stage of infestation by the 
 ,-ed spider. Nearly all le 
 squares, and bolls have been shed. 
 1 1 iriginal. > 
 
 This occurrence was one of the 
 at any time come to the writer's 
 case in this locality (and one of 
 had its origin in a large clump 
 at the edge of town (fig. 9). 
 reached in one direction a point 
 final affected area, semicircular 
 within its confines the occurrence 
 litis was unusual. 4-aav or 5-acre 
 age, arc frequently to be seen. 
 
 severest and most general that has 
 attention. Perhaps the most severe 
 the worst yet seen) was one which 
 of badly infested pokeweed stalks 
 
 The pest spread fanlike until it 
 GOO feet from the pokeweed. The 
 in shape, comprised 13 acres, and 
 was general. While such a case as 
 
 spots, with 25 to 100 per cent dam- 
 
I II I RED 
 
 i • 1 1 ' I i : O > i ii I 1 1 1 N . 
 
 13 
 
 NATl'RAI ' • i\ l in il l l m. \i.| m 1 1 -. 
 
 In both the seasons of L911 ami 1 ■ > I _' red spider occurrence wa 
 
 ~i severe throughout July and earlj August. The last two week 
 
 of August in both cases, however, witnessed so greal n reduction of 
 the pesl that l>\ the end of thai month il was hardl) noticeable, 
 :i rule. This phenomenon, indeed, happens suddenly, and the agen 
 cies which work to produce il are unquestionably of greal economic 
 value. The ageing and toughening of the leaves al aboul this time 
 ni;i\ cause many mites to desert the cotton for other plants, but 
 another factor of probably much greater importance is the increased 
 abundance of several species of insecl enemies which seem to gain 
 dominance nl jusl this time. 
 
 
 
 
 m, 
 
 
 
 
 « 
 
 
 
 
 
 A-P] 
 
 
 
 
 1 •'•' 
 
 1 
 
 - ■ t - 
 
 £**** 
 
 • i 
 
 A* 
 
 L ?i . 
 
 .•» 
 
 >-* 
 
 i \ severe example oJ red-spider work In a cotton Held N'enrlj all plant* In the 
 I nre In the i ondll loi 8. 1 ertaln 
 
 I ■ . . k < - \\ • -i d stnlkf 
 lllnst ration. (Original i 
 
 i MM \ I H' IMI I I M 1 -. 
 
 \- before mentioned, climatic conditions exert a marked influence 
 upon the welfare <>f the pest. During times of little rainfall and 
 high temperature reproduction goes on h\ leaps and bounds; on 
 the other hand, long, heav^ rains work havoc to the red-spider 
 population. In spite of the fad that the red spiders inhabit the 
 underside of the leaves, many are washed off by rains and many more 
 are destroyed by the upward bombardment of -and particles, which 
 may always be seen coating the lower leaves after storms. In fact. 
 it appear- true thai a few heavy rain-, especially if they continue 
 for -mne time, accomplish as much toward controlling the pest as 
 
14 
 
 Till'. I',K1) BPIDEB ON COTTON. 
 
 anything which can 1m> done by man during the season. From obser- 
 vations made, both early in the season and at the beginning of win- 
 ter, it is doubtless true that the young stages are killed by freezing 
 weather. This naturally prevents any considerable winter increase, 
 and in addition some adults probably perish. 
 
 The influence exerted upon the red spider by preseasonal condi- 
 tions appears to be even greater than that of the factors operating in 
 summer weather. The winter of 1J>11-12 was the severest in South 
 Carolina for many years. Hence it might be expected that the fol- 
 lowing season would be a mild one. from the standpoint of injury 
 l>y the red spider, through the assumed heavy mortality of the pest 
 during the winter. On the contrary, as has been stated before, the 
 1912 occurrence was the severest on record. The only possible ex- 
 planation appears to em- 
 brace two suppositions. 
 One is that the adult red 
 spider is little susceptible 
 to extreme cold. The 
 other is that the insect 
 enemies of the mites suc- 
 cumb much more easily 
 to minimum temperature- 
 |i» // v~-# than do the mites them- 
 
 selves. Both of these hy- 
 potheses are sustained by 
 all observations of the 
 
 Fig. l&.—ArtJvrocnodai s,,.. a predaceous enemy of writer. .Naturally, then, a 
 the red spider. At left, mature predaceous larva, severe winter is precise! v 
 magnified 60 times; at right, adult female, greatly 1 ± 1 1 <• 
 
 enlarged. (Original.) " what W<mld mOS * fav ° r 
 
 the subsequent increase of 
 
 the red spider through the destruction of its insect enemies. Con- 
 versely, an abnormally mild winter, free from decidedly low tempera- 
 tures, should furnish conditions most favorable for the survival of 
 the repressive species, and the infestation for the following season 
 would be mild. 
 
 INSECT INI MM s. 
 
 Hot weather, although favoring red-spider development, probably 
 encourages even more the increase of insect enemies, of which sev- 
 eral have been observed. Were it not for these inconspicuous friends 
 of the farmer the depredations to his crops by the red spider would 
 unquestionably be more severe. The following are a few of the 
 more important beneficial species observed during the season of 1912 
 at Batesburg, S. C. 
 
I n I BED SPIDER ON COTTON. 
 
 I.". 
 
 Wthrocnodax sp. 1 (fig. LO). Dunn- the =eae I 1912 a species 
 
 f \rthroonodnx, a ft} belonging to the familj Itonida I formerl) 
 I ulomyiiilw). was first noticed toward the last of June, a1 which 
 "„:,, ,,,,i ;,i all common. It increased wrj rapidly, ho* 
 ever , an d l.\ the end of Juh had become quite abundant, li is the 
 larva (grub stage) of this insecl which assists the farmer, and the 
 attack seems to be limited entirely to the red-spidei I ming in 
 
 contacl with an egg, the larva instantly thrusts its piercing organ 
 through the shell and begins to feed. Large Larva; will dev< 
 egg in from one to two minutes, while the smaller larva? require 
 more time, according to their size. When mature, the larva spins 
 a woolh cocoon 1 mm. 
 
 in length. The adult 
 
 llx issues after a brief 
 
 pupal stage, and the 
 
 full generation requires 
 
 little time. This insect 
 
 i^ probabl) the mosl ef 
 
 fective enemj of the cot- 
 ton mite, and to its final 
 
 superabundance is prob 
 
 :i!)l\ largely due the 
 
 late summer decimation 
 
 of the red spider. It 
 
 has been recorded from 
 
 the follow ing localities: 
 
 Allendale, Anderson, 
 
 Batesburg, Brownsville, 
 
 and St. Matthews, S. C. ; 
 
 Chase City, Va.; Macon, 
 
 Ga.; and Albertville and Boaz, Ala. It evidently has a wide distn- 
 
 ' TripMeps imidiosui Saj (fig. ID- A small anthocorid bug, 
 Triphleps insidi - s Say, was seen as earlj as Maj 16. It is hardier 
 than tin- Arthrocnodas and appears earlier in the season. I hrough- 
 ont July and August it is extremelj common and both in the 
 nymphal and adult stages is second only to the itonid as a red 
 spider enemy. Coming upon a red spider, like a flash the adull 
 
 thrusts its sharp proboscis through the pest's back and proc Is 
 
 quietly to siphon out the body contents. The first victim observed 
 was "drained" in about five minutes, but each succeeding meal was 
 of shorter duration as the appetite became satisfied. The actions 
 of the nymph (fig. 12) are similar, but the individuals obsei 
 were seen onlv to destroy eggs of the spider. In this operation 
 
 Fn .ii / • ■;■■ "' Impoi 
 
 the red spld Mu< b ■ VuUior's 
 
 lllustral V 
 
 i The 'i ''• ' : '- 
 
16 
 
 THE RED SPIDER ON COTTON. 
 
 the proboscis was not inserted far into the ovum, and two minutes 
 sufficed for draining an egg. 
 
 A species of lace-winged fly {Chrysopa quadripunctata Burin., 
 determined by N. Banks) is abundant at Batesburg throughout most 
 
 of the summer, and its larva is doubtless very active in reducing the 
 pest. 
 
 Two species of thrips, Euthrips fvscus Hinds and E. occidentals 
 Pergande, have been determined this season from cotton. They arc 
 commonly found throughout the season about red-spider colonies, 
 
 and may be instrumental in 
 spider destruction. Scolo- 
 f/irlps sexmaciihitits Pergande 
 has been recorded as an enemy 
 of the red spider by Pergande 
 and by Duffy. 
 
 Lady-beetle larvae and adults 
 of several species are com- 
 monly seen on infested Leaves, 
 These are usually either Coc- 
 cinella 9-notata Hbst. or Hip- 
 podamia convergent Giut.. 
 but a small black species, 
 (Scynvrms) Stethorus punctutn, 
 Lee. is frequently observed. 
 The larger beetles are prob- 
 ably more intent upon cotton 
 aphides, but the last-mentioned 
 species, although later in ap- 
 pearing and not overnumerous, seems to be more restricted to the 
 the cotton mite than are other species. 
 
 Fig. 12. — Triphleps insidiosus: Nymph. Greatly 
 enlarged. (Author's illustration.) 
 
 REMEDIAL MEASURES. 
 
 PREVENTION. 
 
 From the abundant experience of the past two years the writer 
 has been forced to the conclusion that the eradication of the red 
 spider must be accomplished through preventive efforts rather than 
 repressive, if it is to be economically effected. The location of the 
 mites through the winter and spring, their preference for the culti- 
 vated violet and the pokeweed, and the manner of dispersion of the 
 pest lead to the presentation of the following cultural expedients. 
 
 Clean culture. — First among preventive measures against the red 
 spider is doubtless that of exterminating the weeds and plants which 
 breed the pest. Pokeweed, Jerusalem-oak weed. .Jamestown weed, 
 wild blackberry, and all border weeds and underbrush about fields 
 should be burned or grubbed out during the winter or early spring. 
 
I ii E Rl D BPIDEB ON COTTON. 17 
 
 This plan has been tested in several instances and has given complete 
 illinium! \ the following season. Too much emphasis can not be 
 placed on the importance of destroying, bo far as possible, :ill weed 
 growth especially the pokeweed, which should be grubbed out l>\ 
 the roots. 
 
 ' 'nil i'ii violets. As before stated, most cases "f infestation in 
 urban localities have their origin in borders "I" cultivated violets 
 growing in near by house yards. In several instances violets adjoin- 
 ing fields of past severe annual infestation have been thoroughly 
 Bprayed, with the result that no red spiders appeared subsequently 
 in these fields. The objection to tin- treatment i- the failure <>n tin 
 part of the average person to persevere with the spraying until the 
 pests have been entirely exterminated. The m<>-t satisfactory pro 
 cedure in such cases consists in the removal and destruction "l the 
 ( [fending violets, 
 
 Varietal immunity in cotton.— Prom several tests conducted in 
 different fields with numerous standard varieties of cotton, and from 
 the information volunteered by farmers from many portions of 
 South Carolina, data have been accumulated which clearly indicate 
 that certain varieties are susceptible t<> red-spider infestation, while 
 others exhibit considerable immunity. Careful observations on a 
 considerable number of varieties grown for the purpose showed thai 
 Dixie "Wilt Proof,*' Toole, Peterkin, Broadwell, and Cook suffer 
 most (in the order named) from the attack of the pest, while Kite, 
 Russell, Summerour "Half and Half," and Cleveland showed the 
 greatest immunity of all the varieties investigated. 
 
 Broadcasted cotton. — An opportunity was accidentally provided of 
 testing the value of thickly broadcasting cotton ;it the boundary of 
 ;i field as ;i trap crop for red spiders. This cotton, intended as ;i 
 cover crop, intervened between the cotton field proper and a large, 
 heavily infested border of violets -a former abundant source of 
 migration. The broadcasted cotton became infested and was later 
 plowed in. The adjoining field remained free from mites. The suc- 
 cess of this experiment would strongly indicate that the cotton trap 
 crop i- a practical cultural expedient to be used in controlling tin- 
 
 pe-t. 
 
 Spacing.— Experiments at Batesburg, S. C, have shown that the 
 red spider commonly travels between plant- upon the ground. This 
 -how- the futility of spacing as a remedial measure. 
 
 Thm of planting. There i- yet much doubl as to the relative ad- 
 
 vantages of early and late planting. Extremely early planting nat 
 urally permit- the plant- to develop a maximum growth of weed 
 and fruit by the time of serious mite appearance. It is noticeable 
 that plant- of considerable size are rarely hilled by the pe-t. nor are 
 well-advanced bolls commonly shed from infestation. On the other 
 hand, several field- about Leesville, S. (\. which were planted 
 
18 THE RED SPIDER OX COTTON. 
 
 late as June 20 seem to have largely escaped the infestation which 
 was so general at that locality. Late planting, however, is almost 
 universally objectionable to the farmer, since in ordinary seasons it 
 results in a reduction of the yield. 
 
 Rotation. — In an effort to test the rotational value of other crops, 
 numerous field crops have been planted in or near infested areas. 
 In addition, frequent examinations have been made of a great many 
 garden and vegetable crop- in infested localities. Besides cotton. 
 red spiders are known to occur not at all uncommonly upon the fol- 
 lowing field crops: Cowpeas, clover, corn. hops, and watermelon. 
 They are also found frequently on the following garden crops: Peas. 
 beans, onion, tomato, lettuce, okra. turnip, mustard, squash, beet, 
 sweet potato, and strawberry. A really acute infestation on corn 
 (as above recorded) was seen at the height of the past season (1912). 
 Cowpeas are particularly attractive to the pest, and sweet potatoes 
 have been noted to be badly infested. Should an immune crop be 
 found and employed, it is extremely probable that the pest would 
 reinvade the fields upon the return to cotton culture with as great 
 ease and quickness as it has done during any previous season, provid- 
 ing the sources of infestation were yet at hand. Rotation, then, does 
 not promise to contribute toward the solution of the problem. 
 
 Effects of fertilizers. — A rather elaborate series of tests with fer- 
 tilizers has been conducted in an attempt to determine whether the 
 various applications assisted cotton to withstand the injurious effects 
 of infestation. Since almost no infestation appeared in these test 
 plats it was impossible to deduce positive conclusions. 
 
 REPRESSION. 
 
 We have just discussed cultural measures which may help to pre- 
 vent infestation. We will now consider what may be done to combat 
 the pest when it has already gained entrance to a Held. 
 
 The writer believes in prevention rather than cure, in the case of 
 the red spider. When once well established in a cotton Held the 
 pest is a most difficult one to wipe out. That it is possible, however, 
 to eradicate the pest from infested fields has been demonstrated be- 
 yond doubt, but in many cases the task i- so tedious that only the 
 most determined farmers will undergo the effort necessary to accom- 
 plish the extermination. 
 
 ll< moral of infested plants. — The experiment ha- been thoroughly 
 tested of pulling up ami destroying the Hist few plant- which show 
 infestation. In such cases the operation was repeated several times. 
 Great care was observed in locating every plant showing the charac- 
 teristic red spots, and these were carefully taken from the Held and 
 burned. If infestation has not advanced far. this treatment is 
 usually satisfactory, and a red-spider invasion often may be " nipped 
 in the bud " and entirely eradicated. 
 
Mil RED -rihi i: ON COTTON. 
 
 19 
 
 [f infestation has spread until a considerable patch has become 
 involved ii is Bometimes advisable, in the case "I" a large field, t" plow 
 up nil the affected portion in order i" Bave the balance of the field. 
 Such ;i drastic measure, however, should orilj be resorted to in es 
 treme cases, and the planter concerned must l>e the j 1 1 « I i-r * • oi 
 ;nl\ isability. 
 
 Occasional observations <>l" instances wherein infestation had 
 abruptly stopped ;it ;i much-traveled road suggested the idea of plow- 
 ing a wide swath just outside the boundary of infestation. This 
 attempted in one case where the occurrence had covered aboiil 2 
 acres. A LO fool ring was plowed around the spot, and all stalks, 
 both in the swath and in the inclosed area, were immediately burned. 
 Unfortunately the farmer did n<»i make sure thai he was beyond the 
 outermost /.one of infestation, and consequently ;i sufficient number 
 of affected plants remained outside the pulverized barrier to con- 
 tinue, somewhat, the dispersion of the pest. This idea should be 
 given further tests, as it seems there should be great efficacy in the 
 operation, provided the swath i- kepi stirred frequently. 
 
 Insecticides. During the season <>f L911, 26 spraj combinations 
 were thoroughly tested under conditions entirely natural. The field 
 used for this purpose was aboul 1 acre in extent, and infestation had 
 become both very genera] and very severe. A strip through the mid- 
 dle of the field, crossing each sprayed plat, was lefl unsprayed t<> 
 serve as m check. Since do substance was discovered which could be 
 safely used to destroy all eggs in one application, it was found nei 
 sary t<> spray twice, with an interval of six or se 1 en days, so as t" de- 
 stroy tlu> hatching larva;. The killing ability of all these sprays was 
 computed, and the percentages ranged from I 1111 to 0. Each of the 
 following six combinations (see Table IV) was found to be very 
 satisfactory. These are presented to indicate the manner of prepara- 
 tion, together with the cost, of LOO gallons <d" each. 
 
 TABl I \ ■tins! th( /< /■. 
 
 
 
 
 i 
 ii 
 
 in 
 
 IV 
 V 
 
 VI 
 
 lions. 
 Flowers of sulphur | 
 
 timi ...| I 
 
 " 
 
 " 
 
 Blacklral tol .unccs, at * 
 
 :; ! 
 •■ U) 111 l^'' 101 
 
 Flowers of sulphur. X . $1.12 
 
 per pourj i 
 Water to m 
 
 JO 75 
 
 1 40 
 
 100 
 100 
 
 - 
 
20 THE RED SPIDER OX COTTON. 
 
 In the course of spraying tests against the red spider on hops in 
 California, conducted by Mr. W. B. Parker. 1 of thi- bureau, it seems 
 to have been demonstrated that Hour paste, used alone or combined 
 with caustic materials, is a valuable acaricide. The function of the 
 flour paste appears to be twofold: Used alone it glues the tiny mites 
 to the leaves, and when added to lime-sulphur, or other solutions, it 
 serves as a spreader to prevent the spray film from breaking up into 
 "• I icads " as it dries on the leaf. Mr. Parker recommends the follow- 
 ing formulas : 
 
 I. Stock solution of flour paste. 
 
 Mix cheap wheat flour with cold water at the rate of 1 pound of flour 
 to 1 gallon of water. Boil to a paste. 
 II. Flour-paste spray. 
 
 Use 8 gallons of the above stock-solution paste to each 100 gallons of 
 water. Keep constantly agitated while spraying. 
 III. lime-sulphur and flour-paste mixture. 
 
 Use 4 gallons of flour-paste stock solution to each loo gallons of lirne- 
 sulphur spray. 
 
 During the recent season no serious effort was made to test addi- 
 tional insecticides. Further use of the sprays mentioned, however, 
 seems to establish the superiority of potassium sulphid, lime-sulphur 
 solution, and miscible-oil-tobacco solution. The last preparation 
 seems to possess better lasting qualities than the others, since, in the 
 absence of rain, one application will also suffice to kill a certain per- 
 centage of the hatching larva?. If one of these were to be used in 
 preference to all others, it would probably be potassium sulphid. 
 This insecticide commends itself from every standpoint — cheapness, 
 simplicity of preparation, ability to kill quickly, and safety of foliage. 
 Altogether it seems to be an ideal red-spider spray. It was found 
 that 100 gallons, wdien applied as a mist spray, about sufficed to treat 
 an acre of average-sized cotton. 
 
 Spraying out-fits. — The sort of outfit to be used for red-.-pider 
 s{3raying depends mainly upon the extent of the occurrence. Some 
 have sprayed their score or so of affected plants with a 75-cent tin 
 atomizer. While this instrument is very economical of liquid and 
 throws a misty spray which penetrates and blows to all parts, it is 
 not economical of time. The bucket pump and knapsack pump come 
 into use in cases of considerable scattered infestation or for the 
 treatment of a few high plants. The most economic outfit for a 
 severe case involving several acres consists of a barrel pump carried 
 through the field on a wagon. One man drives, one pumps, and one 
 handles each sprayer (of which preferably there should be two). 
 Thorough treatment of 3 or -1 acres per day is readily obtainable with 
 this device. For safe work, however, this outfit should 1m? used only 
 
 1 Flour pnstp as a control for red spiders and as a spreader for contact insecticides, 
 Clr. IOC. Bur. Ent, T". S. Dept. Agr., January 30, 1913; The rod spider on hops in the 
 Sacramento Valley of California, Bui. 11", Bur. Ent., D. S. Dept. Agr., 1913. 
 
Ill B BSD BPIDBB ON COTTON. 2 1 
 
 on cotton of average or loti Bize, as the passing wagon will injure 
 large plants. 
 
 \ ' i/ for thorough spraying. Some dissatisfaction has been 
 
 experienced among certain of those who have undertaken to check 
 the ravages of the red spider l>\ spraying. This can be understood 
 on account of the extreme care which must be exercised in order to 
 secure effective results. In the case of insects which devour the plant 
 tissue even the careless application of Paris green or lead arsenate to 
 the top of the foliage is often effective. Tin- is explained by the fact 
 that such pests are constantly moving from leaf t" leaf and will 
 eventually eat some of the poisoned tissue. Moreover, these insects 
 often eat entirely through the leaf, and In 'net' it mat in-- little whether 
 the poison falls upon one side or the other. With the red spider, 
 however, it is altogether different. A contact insecticide is absolutely 
 necessary, and, from the fact that the mite as a rule passes it- entire 
 existence upon the underside of a single leaf, it becomes plainly 
 necessary in spraying to hit tin entire undersidi of < very l<'ii of an 
 infested plant. It is obvious, therefore, thai indifferent spraying is 
 certain t<> yield unsatisfactory results. Furthermore, the absolute 
 necessity for a second spraying to kill the hatched eggs add- to the 
 difficulty. 
 
 It i- hoped that this discussion may impress upon the reader tin 
 • i<r- r, ntion of iii festal ion. 
 
 -t mm w:> . 
 
 The female red spider, appearing to the naked eye like a dot of 
 reddish ink from the point of a fine pen, lays about 50 or 60 round, 
 colorless eggs, which hatch in summer time in about four day-. 
 
 The colorless, newborn spider has six legs, \'rv<\^ at once, and molts 
 in two day- to the primary nymph. 
 
 This first nymphal stage (and all later stages) possesses eight legs, 
 and ha> become larger in size and darker in color. In two more days 
 t in summer) it. in turn, molts to the secondary nymph. 
 
 The second nymphal stage lasts two day-, at the end of which time, 
 after molting, the fully formed adult emerges. Mating occur- at 
 once and egg laying commences immediately afterward-. 
 
 Thus one generation requires in summer weather in South Caro- 
 lina about K> or 11 day-. There are probably about 16 or 17 genera- 
 tions in an average year iii that locality. 
 
 The red-spider colonies live on the underside of the cotton leaves, 
 and their constant feeding causes hlood-red spots to appear on the 
 top- of the leave.-. The effect upon the cotton plant is that the leaves 
 drop, one by one. until usually the plant •lie-. 
 
 The pe-t increases and spreads most rapidly in hot. dry weather 
 until (toward the end id' August I -evcral acre- of a field may become 
 badly damaged. 
 
UNIVERSITY OF FLORIDA 
 
 22 
 
 THE BED SF1DBB OH C< , j| ,l !J^ ll 2 i 'S^^'e""/^^ 
 
 Several insects have been discovered which destroy many mites 
 and are thus of great benefit to the planter. 
 
 At the end of the cotton-growing season most of the red spiders 
 migrate afool in search of greener plants. The majority of those 
 which arc destined to survive the winter probably settle on either the 
 cultivated violet or on the pokeweed. 
 
 RECOMMENDATIONS. 
 
 (/) Clean culture.— Destroy, by burning and grubbing out, all 
 weed, and underbrush about cotton fields, being especially careful to 
 remove all pokeweed. Practice fail plowing so far as possible, 
 
 (2) Control on violets.— Destroy or thoroughly spray cultivated 
 violet plants which may he growing near cotton field-. 
 
 (S) Resistant varieties. — In choosing seed for the crop avoid varie- 
 ties which suffer most from red-spider attack. 
 
 ( .',) Broadcasted trap borders. — Thickly sow cotton along margins 
 of fields at points where infestation has appeared on former occasions 
 and plow these in about dime 1. so as to intercept and destroy the in- 
 vading mites. 
 
 (5) Putting -first infested stalks.— Maintain a careful watch of 
 fields from the time of the earliest appearance of cotton above ground, 
 so that the first attacked plant- may he detected, removed, and burned, 
 thus preventing further spread. 
 
 {6) Barrier strip.— In case a considerable area of cotton has be- 
 come affected before discovery, remove and burn the worst of it and 
 then plow a 10- foot -trip completely around the extreme outside of 
 the infested area. Keep this strip stirred frequently to make further 
 dispersion difficult. 
 
 (7) Spraying.— Apply one of the insecticides recommended to the 
 infested portion of a field before infestation becomes too general to 
 prohibit its use. Choose the pump outfit which hot suits the par- 
 ticular case. Two application- should be made. The second, a week- 
 after the hist, i- to kill the individuals which were eggs at the time of 
 the first spraying. 
 
 Unlike many other pests, the red spider has no wings and spreads 
 mainly by means of its tiny legs. Migration doe- not extend far from 
 its winter quarters. This makes every man'.- problem virtually his 
 own. In other word-, if his infestation always come- from a certain 
 spot upon his premises, proper attention to this -pot will yield him 
 satisfactory results in spite of the negligence of hi- neighbors. 
 
 Approved : 
 
 Jambs Wilson, 
 
 Secretary of Agriculture. 
 Washington, I). C. January ..'.J. WIS. 
 
 O