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Historic, archived document Do not assume content reflects current scientific knowledge, policies, or practices. VIRGIN ISLANDS AGRICULTURAL EXPERIMENT STATION, ST. CROIX, VIRGIN ISLANDS, U. S. A. BULLETIN No. 3. Under the sapenision of the UNITED STATES DEPARTMENT OF AGRIC INSECT PESTS OF COTTON IN ST. CROIX AND MEANS OF COMBATING THEM. BY CHARLES E. WILSON, Entomologist. Issaed May 19, 1923 WASHINGTON: GOVERNMENT PRINTING OFFICE, 1923. VIRGIN ISLANDS AGRICULTURAL EXPERIMENT STATION, ST. CROIX, VIRGIN ISLANDS, U. S. A. BULLETIN No. 3. Under the supervision of the INITED STATES DEPARTMENT OF AGRICULTIRE INSECT PESTS OF COTTON IN ST. CROIX AND MEANS OF COMBATING THEM. BY CHARLES E. WILSON, Entomologist. T Issued May 19, 1923 WASHINGTON: GOVERNMENT PRINTING OFFICE, 1923. VIRGIN ISLANDS AGRICULTURAL EXPERIMENT STATION, ST. CROIX. lUnder the supervision of the States Relations Service, United States Department of Agriculture.] A. C. True, Director. E. W. Allen, Chief, Office of Experiment Stations. Walter H. Evans, Chief, Division of Insular Stations, Office of Experiment Stations. STATION STAFF. John B. Thompson, Agronomist in Charge. Charles E. Wilson, Entomologist. r INSECT PESTS OF COTTON IN ST. CROIX AND MEANS OF COMBATING THEM/ CONTEXTS. Page, Introduction 1 Insects attacking leaf and stem, and methods of combating them 1 Page. Insects attackinsT boll and flower, and methods of combating them__ 10 Miscellaneous notes 20 INTRODUCTION. '^Mien the writer came to St. Croix in June. 1919, the cotton industr}' was at its height. Production per acre had been stimulated by economic conditions brought about by the AVorld War, cotton lint having increased in price from 40 cents to Si. 80 and S2 a pound and the demand for cotton goods being greater than the supply in many parts of the world. With the increase in area devoted to cotton production, the control of insect pests of cotton became a problem of economic importance. The purpose of this bulletin is to describe the life history of some of the insects thus far known to attack cotton in St. Croix and to suggest methods of combating the more destructive species. The insects are treated in the order of their importance as regards attack on the cotton plant, being grouped under two main headings, those attacking the leaf and the stem and those attacking the boll and the flower. INSECTS ATTACKING THE LEAF AND STEM. CoTTox WoEM (Alabama argillacea) . The moth of the cotton worm, sometimes called the cotton cater- pillar, army worm, candle fly, and chenille, is a native of tropical America, being found in South America, Mexico, and the IVest Indies. The adult moth migrates as far north as Canada, but it does not breed outside of the cotton zone, because, so far as it is known, the larvje feed on the cotton plant only. (Fig. 1.) The egg.—The egg, which is about one-fortieth inch in diameter, is light green or light bluish-green, and can readily be distinguished from the leaf after one has become accustomed to seeing it. One or several eggs may be deposited on the underside of the leaf, usually at the top of the plant, but they are never found in clusters. The duration of the egg state is from 2 to 4 days. Low temperature, 1 The writer acknowledges his indebtedness to the experts of the Bureau of Entomology for their courtesy in identifying many of the insects mentioned in this bulletin. The illustrations were supplied by the Bureau of Entomology. 1 2 BULI^ETIX 3, VIRGIN ISLANDS EXPERIMENT STATION. liowever, retards development, and occasionally the period required for hatchino- ma}' l)e from 6 to 10 days. FtG. 1.—The cotton woi-m [AUihaiiKi (ir(/ill<icc<i) : Stapes and work. The larva.—The ego- hatches into a small, inconspicuous, pale yellowish-green worm that feeds for a time upon the underside of the cotton leaf. The color markinos become pronounced as the IXSECT PESTS OF COTTOX IX ST. CROIX. 3 worm grows, and the back of the full-grown worm has a broad brownish or black stripe with a central line, yellowish-green stripe. Similar yellowish-green stripes appear on each side of tj^e black stripe. Each segment of the worm is dotted, four dots being on the back and four on each side. The lateral dots are smaller than the dorsal ones. Color may vary among the ditl'erent individuals in intensit}', but the markings described above are the most constant. Five molts occur during the 10 or 14 days covering the lar\al stage. The larva is very voracious and ruins entire crops unless it is checked. After defoliating the plant and the supply of leaves becomes ex- hausted, it attacks the squares, bolls, and twigs. The larva is always active and travels over the plant by looping—that is, by bringing up the hind pro-legs to the true legs, causing arching of the back in a loop. When disturbed it protects itself by a series of jerks, often leaping 1 or 2 feet horizontally. Its presence in the cotton field can soon be detected by a rather strong odor resembling that of the four o'clock flower. The pupa or chrysalis.—The larva transforms into the pupal stage on the cotton plant, such transformation usually being called " web- bing up." The worm pupates in a leaf which it folds over with a light silken web to form a cocoon. Frequently the pupa is seen hanging from the plant by a thread, but in such cases the leaf in which it was spun has been eaten by other caterpillars. "When it is first formed the pupa is green, but it soon changes to dark brown. The pupal stage lasts from 7 to 10 days. The aduJt.—^The moth may be brownish-gray, olive-brown, or olive-gray. It has a wing expanse of about 1| inches. The upper surface of the anterior wing bears a distinct black spot at about one- third the distance from the anterior to the posterior margins, and the forewings are marked with a number of dark, reddish, wavy, transverse lines. The moths fly at night and hide during the day. Egg laying starts a few days after the moths emerge from the chrys- alis, each female depositing from 300 to 600 eggs.. The moths feed on nectar obtained from the leaf glands of cotton. » CONTROL. Arsenicals.—Paris green mixed with eight times its weight of air- slaked lime has given great satisfaction as a control measure at the experiment station. After it has been thoroughh' mixed the poison should be passed through a fine wire-mesh sieve, placed in a finely woven cotton sack, and slightly shaken oA'er the plants. Yellow cotton cloth is splendid for this purpose. Burning of the leaves was not noticed to occur on plants that had been treated with Paris green and air-shiked lime. Powdered lead arsenate mixed with e(inal parts of air-slaked lime is not as efl'ective as Paris green: and Lon- don purple, owing to its variable composition, can not be depended upf)n for dusting purposes. Xatfrral eneinks.—Two l)irds. tlie gray kingbird {Ti/rannus domi- nicensis domirucensis) and the black Avitcli or Judas bird iCrrjto- phacfa ani), eat large numbers of the larva^ and adults and are of great value in controlling the cotton worm. The jack Spaniard (Polisfes annularis) and the ground beetle {Calosoma calidum) also eat the larvae. Dipterous and hymenopterou.s parasites, inchuling Chcdcis rohusfa, as well as ants and lizards, helj) to control this pest. 4 BULLETIN 3, YIEGIN ISLANDS EXPERIMENT STATION. Blister Mite (Eriophyes gossypii). The blister mite attacks all parts of the cotton plant except the root. When thoroughly infested the plant presents a distorted appearance, being only a mass of warts and nodules which are lined with a thick growth of fine hairs. The mites live and develop within the blisters. The adult is a minute 4-legged mite that can be seen only with difficulty without the aid of a magnifying glass. It severely injures and in extreme cases kills the cotton plant. A closed season is the most effective means of keeping the pest in check. A period of from 2 to 4 weeks is sufficient, and if properly carried out, the law should prove beneficial in the shorter period. The law in St. Croix compels cotton growers to uproot and burn old cotton plants by a certain date fixed for each plantation by the Cotton Pest Commission, composed of four cotton growers and the agronomist in charge of the agricultural experiment station. A period of three weeks is generally designated during which no cotton can be planted. After the expiration of this period the cotton seed is planted as soon as the weather permits. The law gives the privilege of granting different periods for different plantations when no harm is likely to result by so doing. This variation in closed seasons can readily be allowed where a range of hills cuts off one plantation from another, or where each plantation is separated by the distance of a mile or more and the prevailing wind is not in a direction to convey mites from the old cotton plants. The fall army worm, or corn earworm, army cutworm, and south- ern grassworm, ^^^^^s^ V y as it is com- Fall Aemy Worm {Laphygma frugiperda) . 50 to 400 on blades of grass growing on low land. The eggs hatch in from 2 to 6 days. (Fig. 3.) IXSECT PESTS OF COTTOX IX ST. CROIX. 5 The larva.—The larva reaches maturity in from 7 to 12 days. Four molts occur during this period, the first taking jDlace the first day, the second in from 1^ to 2 days, the third in from 2 to 4 days, and the fourth in from 21 to 4 da^^s. When first hatched it feeds upon its eggshell and later on grass blades. The newly hatched worm has a Avhite body and jet black head, but as it grows and molts its body be- comes darker. ^A^ien full grown Fig. 3.—The fall army worm hatched larA-a, or woi-m." enlarged. Newly Greatly it IS about 1^ inches long and varies from light -greenish yellow to almost black. A wavy, yellow- ish lin-^ is found on each side of the body and three narrow stripes run along the back. The dorsal surface of each segment shows four black dots, and the front of the head is marked with a white inverted A. The jmpa.—When it is full grown the larva enters the soil to a depth of from one-half to 2 inches to pupate. The pupal period lasts from 10 to 14 days. (Fig. 4.) The adult.-—The moth varies greatly in color but usually the fore- wings range from dark gra}^ to brown mottled with black and white, and the hind wings have a white, brilliant sheen. The wing expanse is 1^ to 1| inches. ' The body is gray. CONTEOL. Arsenicals.—The grass surrounding the cot- ton field should be dusted with equal parts of arsenate of lead and air-slaked lime before the fall army worm makes its attack upon cotton. Paris green and air-slaked lime should be used as a control measure after the cotton is attacked. XatiiraJ enemies.—^^atural enemies attacking the fall army worm include the gray kingbird, black witch, chickens, ground beetle {Calosoma ealidum) ; hymenopterous insects, including Chaleis rohusta^ Spilo- chaJcis femorata^ S. vittata. and Enicospilus eoneoJor and a dipterous parasite {ExoHsta pyste). Ants and lizards also destroy large numbers of the larvae. -Tlu> fall army I'upa. About natural size. CoTTox-iiOLL CuTWOKM (Prodcnia oniithogaUi and P. latifascia ) . The cotton-boll cutworm, or cotton cutworm, is found throughout the year in St. Croix, and in great numbers from about July 15 to October 1. It attacks the cotton plant soon after the seeds sprout, and later injures the squares and bolls. (Fig. 5.) Cotton-boll cut- worms were veiy numerous in the summer and fall of 1920 and their attack resembled that of the fall army worm. They feed on grasses, Aveeds, niost of the ^ruck crops, and*^the physic-niit ( Jatrop7ia gos- si/plifolia), in addition to tlie cotton plant. Of the two species, P. ornltJiogalU is tlie more common in St. Croix. -Since the life history of the two species is almost identical, only that of P. ornitho- (laUi is fdven. 6 BULLETIN 3, YIRGIX LSLAXDS EXPERIMENT STATION. Fig. 5. Prodenia oniitJior/aJU. Dark form, male above ; pale form, female below. Somewhat enlarged. 27ie egg.—The egg's are deposited in irregular clusters of from 50 to 200 on the undersides of leaves of a number of kinds of plants. They arc usually cohered with brownish-gray down from the body of the female. They hatch in from 4 to 6 days. The larva.—The larvae vary greatly in color, but two distinct forms, the liglit and the dark, are found in St. Croix. (Fig. 6.) The dark form ranges from dark velvety-brown to a rich greenish- black, with two rows of triangular velvety-black spots extending down its back. It is the more commonly found of the two. The light form is similar in appearance, the excep- tion being that it is light velvety- brown instead of black. The larvae complete their development in from IT to 20 days and enter the soil to pupate. They are 1^ to If inches long when full grown. The f upa.—The pupa is dark brow^n and has a smooth, glistening- surface. The pupal stage lasts from 14 to 20 days. The adult.—The adult is a brown- ish-gray moth having a wing ex- i:>anse of 1^ to If inches. The forewings are dark brownish-gray somewhat blotched with white. On the outer margin of the fore- wing there are five wavy lines which are white, brown, broken yel- low, chocolate brown dotted with light gray, and light brown broken by yellowish-white marks, respectively. The hind wings are a glistening pearly white and have wavy light-brown lines extending inside the outer mar- gin. The body is covered with brownish-gray down. Cotton-boll cutworms are controlled by the use of Paris green and air-slaked lime, the mixture be- ing prepared and applied as in the case of the cot- ton worm. Natural enemies play an important part in the control of this pest. West Indian Sugak-cane Root Bouer (Diuprepes abhreciatus) . ^ Fig. 6. Prodenia The West Indian sugar-cane root borer is often p.^ie ''^foim of very destructive to cotton plants about the time lan-a; h, 6aii<. they commence to flower. The adult beetles f^ed on the tender growth of the plant, destroying both leaf and flower bud. One large brood occurs from the last of September to the middle of October, and scattered adults are found every month in the year feeding on a variety of plants. I^'SECT PESTS OF COTTOX IX ST. CROIX. 7 The egg.—The eggs are oblong, white, and glistening. They are deposited on the surface of the leaf, usually of sugar cane or grass, and are concealed by the fastening of two leaves together by the female, or within the folds of one leaf. The eggs hatch in from 7 to 10 days. The larva.—As soon as they are hatched the larva? drop to the ground and feed on the roots of the plant. They are white or slightly yellowish-brown, have a brown head, and a curved body which is footless. They require from 8 to 10 months for development, and feed during this time on the roots of the cotton and other plants. During March larvse measuring from one-sixth to five-sixths of an inch were found at the experiment station. The pujya.—The pupa is very soft and of yellowish-white color. Before pupating, the larva forms an earthen cell in which it trans- forms. The pupal stage lasts about a month. The adult.—The adult is grayish green and has somewhat striated elytra, the stride usually numbering four. An ochraceous-yellow stripe occurs on the lateral side of the thorax, posterior to the eye and along the lower margin of the elytra. The dorsal surface of the thorax and elytra are coarsely punctate. The ventral surface and legs are slate-gray, the beak is thick, and the antennae are long and elbowed. COXTEOL. The adult beetles can best be controlled by hand picking. They do more damage to a cotton crop following cane than is the case when cotton follows cotton. Large numbers of the adults may be trapped by the planting of sunflowers among the cotton. The gray kingbird {Tyrannm dominicensis dominicensis) and the black. witch (Crotophaga ani) are among the important natural controls. Teopical Cutworm {Xylomiges sunia). The tropical cutworm is seldom present in such numbers as to be of economic importance. The egg.—The eggs are pale green and are deposited in clusters of 200 to 300 on the under surface of the leaves of the castor bean, cotton, beet, and chard. They are covered with a light-gray or white down from the body of the female. They hatch in four to eight days. The larva.—The full-grown larvae are from 1^ to 1^ inches long. The dorsal surface of the larva is dark gray, marked with velvety- black patches. The sides are marked with a yellow band. The larval period lasts from 12 to 20 days. The pupa.—Pupation takes place in the soil and lasts from 10 to 12 days. The pupa is brown, smooth, and glistening. The adult.—The adult moth has a wing expanse of from 1\ to 1^ inches. The forewings are grayish-brown and the hind wings are a glistening pearly white. CONTROL. Dusting cotton -for the control of the cotton worm (Alahama argillaeeei) will also control the larva? of the tropical cutworm. The parasitic fly, Exorlsta py-^te. is a natural means of control. 8 BULLETIN 3, VIRGIN ISLANDS EXPERIMENT STATION. Cotton Aphis (Aphis gossypii). The presence of the cotton aphis, also known as the melon aphis, plant-louse, and cotton louse, can be detected by the curled and blis- tered appearance of the leaves. The insect occurs abundantly on young cotton in ^St. Croix, especially when the weather is dry. (Fig. 7.) The nymphs and adults seriously check the growth of the young plant by sucldng its juice. No permanent injury has as yet been observed, probably because as the insects become abundant their natural enemies increase in number sufficient to destroy them. Fig. 7. Aphis gossypii: a, Winged female; aa, enlarged antennae of same; ah, dark female, side view ; I), young nymph or larva ; Cj last stage of nymph ; d, winged female. All greatly enlarged. The adult is green or brownish-green, winged or wingless, and soft bodied. The nymphs, or young aphids, are similar in appear- ance, except that they are wingless. Nymphs and adults are found together in colonies on the underside of the leaf. They prefer tender growth and young leaves for food. CONTROL. Measures are not necessary for the control of aphids on cotton. They are naturally controlled by two enemies, a parasitic hymenop- teron {Lysiphlebiis Jestaceipes) and a predacious ladybird beetle {Cycloneda sanguinea), usually called the "red ladybird." During February and March about 93 per cent of the aphid colonies were parasitized by Lysiphlehiis testaceipes. Other enemies of the cotton aphis are the lace-winged fly larvae and the syrphus-fly larvae. IXSECT PEST? OF COTTOX IX ST. CROJX. 9 Cotton Lace-bug i Coriithuca gossijpii Tlie common lace-biig rarely causes much damaofe to cotton, but A'ery seriously injures the leaves of the castor bean (Ricinus com- Tii link). The eg<]:s of the cotton lace-bug are somewhat flask-shaped and are deposited within the tissue of the leaf. In a few days they hatch into wingless nymphs, which congregate in colonies Avith the adults on the underside of the leaf. Both nymplis and adults feed by insert- ing their beaks into the tissue and sucking the plant juices from the leaves. This causes the leaves to turn yellow and die. Lace-bu<rs rarely become numerous enouHr on cotton to cause severe damage. Red Spider {Tctninvchus telarius). The red spider, or spider mite, is of very slight economic importance in so far as its attack on cotton is concerned. It is found on the cotton plant during extremely dry weather only. Irs native food plant is a weed (Leonotls nepe teefolia), locally known as ''hollow stock." (Fig. 8.) It can best be con- trolled by the destruction of this weed. Scale sects a^td Mealybugs. Scale insects and mealybugs rarely be- come numerous on cotton until about the time the plants are to be destroyed. The West Indian or white-peach scale {Aidacaspis pentagona) rapidly in- creases in number on old cotton plants and soon covers stalks and st ms. This pest can best be controlled by the destruc- tion of the plants. The black-shield scale {Saissetia nigra) is commonly found on cotton from December to April, but can not be considered a serious pest, because it is controlled by a minute parasitic hy- menopterous insect known as Zaloph- thrij- minim. The black scale {Saissetia oleoe) attacks cotton too late in the season to b? of economic importance. By a rigor- 6us observance of the cotton-pest law this scale can be destroyed. The hemispherical scale (•S'. hemispharica) has not been found on cotton in sufficient numbers to necessitate the use of control measures. The destructor scale {A^pidiotus destructor) has been found only on old leaves. Measures for the cr)ntrol of this scale insect on cotton are not necessar}'. The spotted mealybug {Pseudococcus virgatus) and the long- tailed mealybug (P. Jongispirnis) are usually found inside the calyx and are controlled bA' natural enemies. The red ladvbird beetle Fig. S The red spicier. Teirnny- chus telarius: AdulL female. Greatly enlarged. 10 BULLETIX 3, VIRGIN ISLANDS EXPEPJxMEXT STATION. {Cijcloneda sa-ngu'm.ea) and its larvse are among the important natu- ral enemies. Lesser Cottox Woem ( Alctia luridiila) . Larviie of the lesser cotton worm are generally found with the larvae of the cotton worm {Alabama argillacea)^ and on account of their h3,bits, manner of feeding, and appearance they are usually mistaken for the latter. The larvse of the lesser cotton worm differ from the cotton-worm larvse in size and color, being smaller and reddish brown. The pupal stage is spent in the soil. The adult moth is smaller than the cotton-worm moth, and is a dull gray or reddish brown. CONTROL. The lesser cotton worm can be controlled at the same time the cotton worm is checked by the use of arsenicals. Spotted Flea-beetle {Homopliceta cequinoctialis) . The spotted flea-beetle is usually found feeding on cotton leaves from February to April, but is never present in such numbers as to attract attention. No control measures are required for this species. Greenhouse Thrips {HeliotJirips hwmorrhoidalis) . Greenhouse thrips have been taken from cotton, but never in suffi- cient numbers to warrant the use of control measures. A small brown thrips (probably Frankliniella gossypiiA) has been taken from young leaves surrounding dead flower buds. Sick Cricket {Amphiacusta caraihce). The sick cricket is usually found beneath the calyx. It is an indis- criminate feeder, but has not been found in large enough numbers to necessitate the use of control measures. This species feeds at night. Sphinx or Hawk-moths. • The sphinx or hawk-moth species that have been reared from cot- ton are the white-lined sphinx (Deilephila lineata), tomato-worm moth (Protoparce rustica), tobacco-worm moth {P. sexta), alope sphinx {Erinnyis alope) ^ and ello sphinx {E. ello). The presence of sphinx moths on cotton may be called accidental. They never occur in such numbers as to require the use of control measures. Snowy Tree Cricket {QJcanthus niveiis). Few specimens of the snowy tree cricket are found on cotton. The female deposits her eggs on the cotton stalk in rows, forming long scars. The snowy tree cricket may be classed as beneficial rather than as injurious, since both young and adults feed on aphids. INSECTS ATTACKING BOLLS AND FLOWERS. Pink Bollworm {Pectinophora gossypiello) . The pink bollworm is very destructive to both cotton lint and to cotton seed. It stains the lint, causes it to be short and kinky, and IXSECT PESTS OF COTTOX IX ST. CROIX. 11 more or less cements the lint and seeds together. It greatly reduces the yield of lint and the amount of seed produced. The seed is also of light weight and germinates poorly. The pink bollworm may be found in one or several locks of the boll, but on? worm seldom at- tacks more than one lock. (Fig. 9.) Counts of bolls on plants taken at random from the field during Jan- uary. F e b r u a r , March, a n d the early part of April, 1921, showed that from 5 to 25 per cent of the 1921 crop was a loss. On this account the old cotton plants were not removed from the fields and no new crop was planted. The bolls on old cotton plants showed 30 per cent infestation on February 11, 1922. (Fig. 10). This con- dition was reported to the Cotton Pest Commission, and within a few days the removal and destruction of all cotton plants was requested. Fig. -The pink boUwoim ( Pcctinophora gossypieUa) Adult. Much enlarged. Fig. 10.—Exit holes of pink boUworms in cotton bolls;. The egg.—The eggs of the l)ollworm are deposited singly near the points of green bolls in the sutures marking the locks. A number of 12 BULLETIN 3, VIRGIN ISLANDS EXPERIMENT STATION. eggs are often found on the same boll. They hatch in from 4 to 12 days. The larva.—The white or yellowish-white larva bores its way into the boll almost as soon as it is hatched. After entering the boll it feeds upon the seeds, which it cements together. Cementing of the seeds is a characteristic feature of the work of the pink bollworm. The larva becomes pink as it develops within the boll and measures one-half inch when fully grown. (Fig. 11.) In St. Croix the larval period usn- ht conditions apparently pro- ne. 11. -The pink bollworm : Outline drawing of larva, showing structure. Much enlarged. Drou< ally lasts from 12 to 11 days, long the period. The pupa.—Before passing into the pupal state the larvae usually spend one day in a prepupal stage. The pupa is brown or reddish brown. The prepupal and pupal period lasts from 9 to 12 days dur- ing February and March. The pupal period of three specimens lasted 22 days in March, 1921. (Fig. 12.) The adult.—The adult moth is dark brown or dark grayish brown and has a wing expanse of from two-thirds to seven-eighths of an inch. Ths forewings are somewhat narrow, pointed, and edged with long brown fringe. The hind wings are somewhat broader, more pointed, and edged with longer fringe. They are usually lighter in color than th ^ forewings. In St. Croix the minimum time required for de- velopment from the egg to the adult stage has been 28 days, and the maximum time under laboratory conditions has been 42 days. CONTROL. At the present writing cotton growing in St. Croix has b:en suspended. It is hoped that no cotton will b? planted for a period of three years or more, as a closed season is the only practical m6ans of control so far known. Adult moths of the pink bollworm have been found infested with numerous predacious mites of the genus Pediculoides. When these mites crawl upon the hands and forearms of the pickers fig they cause severe irritation which results in dermatitis. 12.—The pink IwUworm : Pupa. Much enlarged. Southern Green Stink-bug (Nczara viridula). The southern green stink-bug, also known as the stink-bug, bush bug, green plant-bug, green soldier-bug, green bug of India, pumpkin bug, green bug of cotton, shield bug, and green shield bug, is now found in tropical and neotropical regions all over the world. The IXSECT PESTS OF COTTOX IX ST. CROIX. 13 southern green stink-bug inserts its beak into cotton bolls when feeding and thus introduces the fungus causing internal boll disease. (Fig. 13.) The egg.—The eggs are deposited in compact, hex- agonal clusters on the u n d e r surface of tomato, tobacco, okra, corn, and many weeds, the individual eggs being firmly glued together in very regular rows. The egg clusters are Av h i t e or creamy- white when first de- posited and later be- come broAvnish-pink. Shortly before they hatch, the eggs pre- sent a reddish ap- pearance, the color of the nymphs being visible through the shell. The egg clus- ters contain from 48 to 118 eggs. Under laboratory c o n d i - tions the eggs hatch in from four to eight days. (Fig. 14.) 27ie ni/mph.—F\\e molts occur during the nymphal period. The nymphs of the first instar molt in from 2^ to 4 days; those of the .-econd. in from 5 to 12 days; those of the third, in from 2 to 8 days; those of the fourth, in fi-om 5 to 10 days ; and those of the fifth, in from 5 to 20 days. (Fig. 15.) The most rapid de- velopment takes place from Sep- tember to January. The adult.—The adult is light green, shield-shaped, aud varies considerably in size in V)oth male and female. Both adults and nymphs emit a malodorous sub- stance for protection. -Southern green plant-bug Adult. Enlarged about 4 i ~Sezfira viridiila i diameters. Fig. 14.—Southern green plant-bug : Egg- cluster, viewed from above. Enlarged about 6 diameters. hand is the most satisfactory gi'een stink-bug on cotton. CONTROL. Hand picldng.—Picking by method of control of the soutliern 14 BULLETIN 3, VIRGIN ISLANDS EXPERIMENT STATION. Natural enemies.—A dipterous parasite {Trichopoda pennipes) is tlie most important natural control for the ^rreen stink-bug in St. Croix. Field collections of Nezara viridula show that the largest amount of parasitism occurred in Januar}', when 93 per cent of the Fig. 15. Nezara viridnJa: Nymph, fifth instav ; light and dark types. Enlarged G diameters. specimens were parasitized. The smallest amount of parasitism occurred in July, when field collections showed 12.28 per cent of the specimens parasitized. (Fig. 16.) The black witch and the gray kingbird eat both nymphs and adults of the southern green stink-bug. IXSECT PESTS OF COTTOX IX ST. CROIX. 15 Cotton Stainer (Di/sdercus andrra). Cotton stainei-s are always abundant on cotton bofe during the winter and early spring months. Only one species is found in St. Croix. The insect is called the cotton stainer because it injures the cotton by staining the lint. The €(/(/.—The eggs are laid in clusters on the ground or dropped into opening cotton bolls. They are small, yellow, and glistening. The nymph.—The nymphs are red in color. The development of the nym2:)h is gradual. The adult.—The adult cotton stainer is red, black, and white. The head and the thorax are red. The latter has a white line on the an- terior and posterior margins. Just inside this margin there is a black line. "When the wings are folded the dorsal surface is marked with a large white X. Between the upper arms of the X the color is red or reddish-black, while between the lower arms of the X the color is black. A red triangle containing a black spot is found on each wing cover. The lower surface is red and the legs are black red. Both nymphs and adults live by sucking the juices from the bolls. The staining of the cotton lint takes place when the insects feed. COXTROL. Cotton stainers can -best be con- trolled by picking by hand and by trapping. The stainers congregate in groups on the cotton bolls and can be brushed from them into pans containing a little water and kero- sene. Handfuls of cotton seed, dropjDed on the ground between rows of cotton, attract large num- bers of the stainers. Boi.LwoRM (Hcliothis obsoleta). The bollworm, cotton boUworm, corn earworm, tomato fruit worm, and budworm, as it is called, is found in most of the tem- perate and tropical regions of the world. (Fig. IT.) The larvae feed on a large variety of plants, but severely injure corn, cotton bolls, tomatoes, and tobacco. The efjrj.—The eggs are small, wliite in color, and are oviposited on the leaf or fruit of the liost plant. Thev hatch in from 2^ to 7 days. The larva.—The larva, upon liatcliing. feeds upon the eggsliell and then upon the host plant. At this time it has a yellowish-white body and a black head, ^ix molts occur during the larval period. The adult larva? vary greatly in color, ranging from pale green to pinkish, gray green, light and dark brown, grayish black, and almost black. The full-grown larva is al^out 1} inches long, and pu})ates in tlie ground at a depth of from 2 to 4 inches. (Fig. 18.) Fig. — Trichopocia penuipes. Adult fly, three times natural size. 16 BULLETIN 3, YIEGIN ISLANDS EXPERIMENT STATION. The 2)upa—The pupa is incased in an earthen cell. The pupa is a smooth, shining- bro^Yn in appearance. The pupal stage lasts from 14 to 18 days. (Fig. 19.) 2'he adult.—The adult moth has a wing expanse of from 11 to 1% inches. The adult ranges in color from pale grayish green to almost brown. (Fig. 20.) Fig. 17.—Cotton boll with full-grown bollworm eating into tip. CONTKOL. Large numbers of the bollworm larvae are killed by the use of Paris green when it is applied to the cotton plant for the control of the cotton worm {Alahama argillacea). The bollworm is parasitized by the following hymenoptera: Chalcis Tohusta, C. annulata (?), Spilochalcis femorata^ S. vittata^ and Enicospilus concoloi\ and by the fly Exorista pyste. The preda- IXSECT PESTS OF COTTOX IX ST. CROIX. 17 ceoiis ground beetle Calosoma caJuhim eats the larvje when they drop from the plant to pupate. The adult moths are caught by the gray kingbird and the black witch. Fig. 18.—Three cotton boUworm larvtE, seen from the side, showing color types. Upper larva, green ; middle larva, rose colored ; lower larva, dark brown. Flower-bud Maggot (Contarinia gossypH). The flower-bud maggot occasionally attacks cotton flower buds in St. Croix. Its presence may be noted by the flaring of the bracts of a h Fig. 10.—Adults of cotton bollworm : a. With winjrs spread : h, in resting position, wings folded. Twice natural size. the flower buds. This worm causes the squares to drop, resulting in a small crop. The eggs are laid in the young flower buds of cotton. On hatcliing. the laiwK feed inside the flower bud. causing the death of the bud. 18 BULLETIX 3, YIRGIX ISLAXDS EXPERIMEXT STATIOX. The larvae are yellowish-white or pinkish in color and when full grown are about 2 millimeters long. Pupation takes place in the soil. The adult fly is a minute insect, about one-sixteenth of an inch long. The face is fuscous, and the eyes are large. The scutellum is yellowish and tlie abdomen greenish-yellow. The flower-bud maggot has not been found generally distributed in the cotton fields during the past three years, and control measures have not been n:eded. BoLLwoR^t (Heliothis virescens). The bollworm, also known as the tobacco budwoim, is usually found with the cotton bollworm {H. ob^oTeta). The habits of the two species are the same. Only a few larvae have been taken from cotton bolls in St. Croix, but they have been present in some num- bers in okra pods and tobacco-se?d pods. The life histories of H. obsoleta and 11. virescens are almost iden- tical. The full-grown larvae are usually yel- lowish-green and pupate in the soil. The adult moth has a wing expanse of 1^ to 1^ inches. The forewings are olive green crossed transversely by three lighter col- ored lines. The hind wings may be a shining white or white with the outer third brown or pink. CONTROL. This species is controlled by the same method used to combat the cotton boll- worm (Heliothis oljsoleta). I'lXK Scavenger Worm { Pijroclerces rileiji) . The larvae of the pink scavenger worm or pink cornworm has been found only in diseased bolls or bolls in which pink bolhvorms {Pectinophora r/ossypielJa) have worked. It can not be considered a pest of cotton. The egg.—The eggs are small, pearly white and shining. They are deposited singly or in groups of 3 or 4 between rows of grain, on ears of corn, and on corn silks. The larva.—When they are first hatched the larvae have creamy or yellowish-white bodies and a dark head. The body soon changes to pinkish color, but the head remains dark. When they are full grown the larvae measure about one-third of an inch in length. The pu2)a.—The pupa is a light yellowish-brown and is smooth and shining. The adult.—The adult moth has a wing expanse of one-third to one-half inch. The forewings are ITimded and mottled with yellow,' light brown, and black. About two-thirds of the basal margin has long fringe. The hind wings are very narrow and have very long fringe on the basal portion and shorter fringe on the anterior mar- FiG. 20.—Pupfp of cotton boll- worm. Twice natural size. IXSECT PESTS OF COTTOX IX ST. (^KOIX. 19 gin. The color of the liind wings is grayish-brown. The adult inotli IS very active. Control measures are not necessary for this species on cot (on. Zex odoc h ium c rrij icol klla . This motli is found only in diseased bolls or in bolls that have been attacked by tlie bollworni. It can not be considered of economic iniiK)rtance to the cotton croj). I'l.AXT-r.rt; ( /'////( d it'n iii ) . This i)lant-bug is commonly found in St. Croix, but seldom attacks cotton. Its favorite food plant is the fireweed {Pdfura metel). Unless the field is kept free of this weed. P. picta may be expected to attack cotton bolls. The eggs are brown and are deposited in clusters of 10 to 90 on either surface of the leaves of fireweed (Datura inet('l). They hatch in from 4 to 8 days. The nymphs are red and congregate in groups. The adult is dark brownish- black. Avith a narrow orange- red line on the anterior and lateral margins of the thorax, and a broad yellowish or orange-red band on the l)os^ terior margin. This band is absent in some specimens. I>otli adults and nymphs feed by sucking the juice from the plant. (Fig. 21.) CONTROL, I'u;. --'I, -I'lithUi ijicta: Adult iii:il< Much en- Picking l)y hand is probably the l)est method of controlling P. pirta on cotton. The bugs can (>asily be knocked into receptacles containing water and kerosene if tlie plant is jarred. SiMM.i) SiTM-:-i!r(. {.\rr<liii.s a Ih'iini iicl al lis ) . 'J'he si)ined stink-bug has not been found in suHicient numbers to lie of economic imi)ortance. Its habits and life history are almost identical with those of the southern green stink-bug iX."?((m viri- (hihi). In its nymplud stage .1. allxfjuinrfafu.^ is dark reddish-brown in color. Measures ai'e not needed to control this insect. 20 BULLETIN 3, VIRGIX ISLA]SrDS EXPERIMENT STATION. Laege SqUxVSh Bug {Leptoglossus gonogara). The large squash bug is more frequently found attacking guava {Psidium guava) than any other plant. These bugs rarely become numerous enough on cotton to attract attention. The eggs are laid in a single ro^Y, usually on the stem of the plant. They hatch into red and black wingless nymphs, which molt several times before reaching the adult stage. The adult is a large brownish- black bug. Both nymphs and adults feed by sucking the juices from the plant. The large squash bug is best controlled by hand picking. The nymphs and adults are easily brushed into a receptacle containing water and kerosene. The writer has made no effort to systematically collect the Orthop- tera, Hymenoptera, Diptera, and Neuroptera that frequent the cot- ton plant. The three species of economic importance are the assassin bug (Zelus longipes), a praying mantis, and a lace-winged fly or aphis-lion. These insects are predacious on insects attacking cotton. Z. longipes is found feeding on lepidopterous larvae and nymphs of other Hemiptera. The praying mantis feeds on a number of different species, and the lace-winged fly in both larval and adult stages feeds upon aphids. COXTEOL. MISCELLANEOUS NOTES. o