Historic, archived document Do not assume content reflects current scientific knowledge, policies, or practices. ~ a n * : . ' estes fr Pree yy hp ate) Peer ‘) ‘ * g oie i ie r Fo / t. ' i “A a» ~ . - a1) UNITED STATES DEPARTMENT or AGRICULTURE DEPARTMENT CIRCULAR 288 Washington, D. C. September, 1923 | THE PUSS CATERPILLAR AND THE EFFECTS OF ITS STING ON MAN. F. C. BISHOPP, ENTOMOLOGIST, BUREAU OF ENTOMOLOGY. CONTENTS. Paze Page Distribution........- as Aaa ie ea es ce a 1 injurlousnessSe ae ee eee Panna LOS TDIANUS Hee oat ae eae eee ee Lee 2 Natural: controle scence aeons cite semen iWyacs DESCrIpMOMOLStageSe ras. 2 2) sess ce |e 2 Riemedialsmeasutesysssase ese esse eee ace 14 Life history and seasonal history....-......... 4 There are about 25 species representing about 8 families of lepidop- terous larve the bodies of which are supplied with urticating hairs or spies which produce more or less painful stings when they come in contact with unprotected portions of the skin of man. Among these Megalopyge opercularis S. & A. produces the severest sting of all the forms occurring in the United States. In the South these cater- pillars sometimes become so numerous as almost to defoliate shade trees,but their principal claim upon our attention is their sting. The occurrence of this caterpillar in great abundance during a number of seasons in the last 8 or 10 years has given it considerable notoriety in the South. It has been termed “Italian asp,” “‘ possum bug,” “puss caterpillar,’’ and, by the Mexicans, “perrito,’’ meaning little dog. Each of these names is assigned on account of some habit or appearance of the caterpillar. DISTRIBUTION. The species has a rather wide distribution throughout the Southern States. It has been taken as far north as Virginia, is common in Florida, and is not infrequently met with in the central Southern States, but appears to attain its maximum abundance in Texas, especially from Dallas southward in the central western part of the State. The related species Lagoa crispata Packard is very commonly met with throughout the Northern States, but its stinging propensi- ties are not highly developed. The family Megalopygidae is rather large and especially developed in the Tropics, many of the species being fairly large and several possessing urticating bristles. 53529°—23 D) Department Circular 288, U. S. Dept. of Agriculture. HOST PLANTS. Megalopyge opercularis has a rather wide range of host plants. It has been reported by Watson* and others as feeding regularly on ~ ‘ | citrus trees in Florida, and in the writer’s work in Texas has been | taken commonly on hackberry (Celtis occidentalis), elm (Ulmus, two or three Bice cultivated and wild plum (Prunus spp.), sycamore __ (Platanus occidentalis), and oak (Quercus, several species), and fre- uently on rose bushes (Rosa spp.). The trees are listed in about the order in which they are pretarred by the caterpillars as food. DESCRIPTION OF STAGES. = THE ADULT. Both sexes are yellowish brown, the wings being clothed with rather long wavy hairs, some of which are white, especially along the veins, giving an appearance of silvery streaks. The forewings are strongly marked with dark brown, particularly toward the Fic. 1.—Male moth of the puss caterpillar. anterior border. The wing spread of the female is nearly 14 inches, and the male is somewhat smaller. The legs are also covered with long hair and the tarsi, being black, contrast rather strongly with the lighter hairs above. (See Figs. 1 and 2.) THE EGG. Why ese 4 The eggs are pale yellow, elongate oval, the sides nearly parallel for some distance and the ends bluntly rounded. The average length is about 1.2 millimeters and the — width 0.6 millimeter. The eggs are laid in rows in the form of an arc, usually 8 to12_ eggsinarow. Sometimes two or three parallel rows about one-fourth of an inch apart are deposited, the female moving forward a little after each row is laid. As the eggs are deposited the tip of the abdomen is swung laterally, the head of the moth serving as a plvot. Occasionally one row of eggs is laid directly on top of another. Nearly always the eggs are well covered with the long yellowish hairs from the abdomen of the moth (Fig. 3), and when the insect has completed oviposition the body is often practically denuded of hair. The head end of the embryo is toward the center of the © circle. The eggs are usually deposited on the leaves of trees. ta gs eae a 4 “> Aes + | ; 1 Watson, J. R. Insects of a citrus grove. ' University of Florida Agricultural Experiment Station Bul- — letin 148, p. 245-246. June, 1918. The Puss Caterpillar. 3 THE LARVA. The first instar is about 1.5 millimeterslong. The color is usually yellowish with a slight reddish tinge. Each of the body segments is provided with protuberances on each side crowned with hairs, some of which are one-half to two-thirds the length of the body, and among these hairs occur rather strong spines. These spines are only slightly developed on the posterior segments. In the second instar the length of the larva is about 2.3 millimeters, the color usually rather uniformly reddish yellow, the greatest width at the anterior thoracic segment and tapering toward the posterior end. The body is fairly well covered with tufts of rather long hairs intermixed with other hairs somewhat wavy and often equal in length to the body. In the third instar the larvee measure 3.1 millimeters in length. The hairs appear longer, more numerous, and rather lighter in color than in the previous instar. In the fourth instar the larvee Fic. 2—Female moth ofthe puss caterpillar. measure about 3.6 millimeters in length. The hairs are more thickly set than in earlier stages and are inclined to recurve, especially in the middle of the body, giving a matted or bunched appearance. ‘There is apparently an increase in the number of urticating spines with each molt. It is believed that there are five or six instars, but owing to high mortality and over- lapping the later stages have not been definitely separated. In the last stages the larvee are well covered with hair, which lies rather flat, extending downward to the surface upon which the insect rests. The larve are considerably deeper in the thoracic region and taper toward the posterior end, the hair at that end being tufted to form a Sort of tail. (See Fig. 4.) The hairs all arise from rather definite circlets, three rows of which are present on each side, the dorso-lateral ones being the largest. Among the hairs on each of these convex areas are numerous smooth yellowish spines with almost black tips. (See Fig. 5.) The dorso-lateral rows contain from 100 to 125 each, the lateral from 50 to 60, and the ventro-lateral rows 20 to 30 each. Close to the base of the legs and the pseudopods is a row of small folds bearing some hair on their apexes, pee apparently not provided with spines. The length of the mature larva is about 1 ‘inc 4. Department Circular 288, U. S. Dept. of Agriculture. The color in these later instars is extremely variable, being pale yellow, gray, red- dish brown, or mouse color, and some few present mixtures of colors. These colors change with the molts and do not seem to be correlated with age or food plants. THE COCOON. The cocoons are spun on the trunk or small branches and occasionally on the leaves of the host trees. The first silken structure (Fig. 6) is elongate oval, and within this is formed the more dense and tough urn-shaped cocoon with its char- acteristic hump in the middle over the thoracic region and beautifully con- structed beveled-edge operculum (Fig. 7). Practically all of the long hairs are shed Fic. 3.—Eggs of the puss caterpillar on leaf, covered with hairs from body of moth. by the larva as it spins and are interwoven with the silk, thus giving the cocoon nearly the same range of color as shown among the caterpillars. The ventral side of the pupa is shown in Figure 8. LIFE HISTORY AND SEASONAL HISTORY.’ The insect spends the winter in the larva stage within the cocoon. Pupation takes place in the early spring and the adults emerge in April, May, and June. The moths in emerging from the cocoon often leave the exuvie projecting from the operculum (Fig. 9). 2 In the life-history work carried out in 1914 the writer was materially assisted by W. E. Dove. — i ~ The Puss Caterpillar. 5 They are comparatively sluggish and usually mate soon after becom- ing dry. The eggs are usually laid by the females on the leaves nearest at hand. After oviposition there seems to be more tendency for the moths to fly and they are occasionally seen around lights in a city. The females usually begin deposition the day following emergence and will lay many eggs even though not fertilized. No indication of parthenogenesis has been noted. The number of eggs deposited ranges from 300 to over 600. Oviposition is usually com- pleted in 2 or 3 days, but may extend over a period of 7 or 8 days. Fic. 4—Full-grown puss caterpillar. The females usually die shortly after egg laying ceases and the males live from 4 to 9 days. Oviposition proceeds freely without the moth partaking of food, and it is believed that normally the adults do not feed in nature. The duration of incubation has been observed to range from 4 to 8 days. The segments of the young larve can often be seen through the eggs several hours before hatching begins. In hatching the egg is broken open at the tip by the larva and usually a portion of it is eaten away, thus leaving a ragged end. The young larve feed eregariously for several days, the leaves at first bemg minutely skeletonized as shown in Figure 10. Later, usually in the third instar, the larve begin to cut through the entire leaf. Tables 1 and 2 give some of the data obtained in the study of this insect. 6 Department Circular 288, U. S. Dept. of Agriculture. TaBLE 1.—Megalopyge opercularis: Pupal period, oviposition, and incubation at Dallas, Tex. : Number of moths. Period from . . Date cocoons were spun or | Period ofadult | spinning or eats ia collected. emergence. collecting to = : emergence. | Male. ee sextet tion. ing- 1914. | Collected: Days. | YT Ry aaa eames Auge 3i-to Oct. 7-14 to 40-F 2) 2 13 3 12 | Sept. 1) Sept. 6 Piste See Sept.5 to Sept.6..|9tol0+......| 2] 1 0 | Sept. | Soptrag = ee eee Sept. 21 to July 18.| 2to0302+....| 2 1 Pe eee mre DEC Gi: oe 6 eee Ma yiSootne hess ela eas seo oe Dig ees ore May 7 None. Spun: Oct; 2005.35 ss eee May 5 to May 8 -..-.| 197 to 200+-..-}.....- 2 Bi = cee 29. Sool ese eeaee Apr 24 ees se cy Geen egal oe A Ree a eee 1916. Octesi a5. eee May 30 (before) =: | 20 — = ee 2 et ee eel ies ee, ee 1920. | duly355 = S265 eee eee SAI. Wear sae ae Soa seeneesete 1 eS eS Sea Aer ee te iis 22 eens AUST cee eee eee Paleo octee ee 32 3| Sees Collected | SAL y230 5 Se Sas meee July 31 to Aug. 18-/ 1 to19+....) Il Ooh c= Aug...4 | nue. 7. BOs heme eee July 31 to Aug. 26.| 1 to 27-++-..---| Op ES gl Gee eee doz AS 4. 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Jo quoudoparvag :siopnoseado ablidoppboyy —% AAV, 8 Department Circular 288, U. S. Dept. of Agriculture. The duration of the early instars has been determined rather accurately, as shown in Table 2, but no individuals have been carried completely through their development under close observation. This has been due to the large percentage of mortality from disease, especially when the larve are kept in confinement. Development is comparatively slow, and apparently 30 to 60 days are necessary for growth to be completed. In Dallas the maximum number of grown larve of the first genera- tion seem to occur in June and July, and of the second generation in September and October. There has always been more or less over- lapping of the two generations, however, and in some strains probably lia. 5.—Puss caterpillar with most of hairs removed to show clusters of spines. there is but a single generation in a year. Pupation of the first generation usually begins early in July and extends through the month, and with some individuals much later. The duration of this stage in the first or summer generation ranges from 28 to 41 days (see Table 1). The cocoons of this generation are to be found well scattered over the trees, frequently being attached to the leaves but more commonly to the twigs and branches. The spinning of the cocoons of the second generation begins in September and extends until heavy freezes occur. With this generation there is a marked tendency to spin up on the larger limbs and trunks of trees, and apparently a greater number leave the trees entirely and crawl about in search of suitable places for pupation. The tendency to spin up in crevices and other protected places is much more marked in this than in the summer generation. The crevices in the rough The Puss Caterpillar. 9 bark of the hackberry trees are often seen to be filled with cocoons, sometimes thousands of them being present on a single tree. Occa- sionally they are seen on fences or houses, or on stones around the bases of trees. INJURIOUSNESS. As has been stated, the caterpillars can be considered of com- paratively little importance as enemies of shade trees, although on Fie. 6—Cocoon of puss caterpillar attached to twig, side view. certain occasions they become so numerous as to defoliate them almost completely. This phase of the injury done by them will not be discussed. All stages of the caterpillar are capable of stinging. The severity of the sting, however, increases with the size of the caterpillar. Freshly molted skins and recently killed larve will produce mild stings and the larve after the cocoon is spun are capable of stinging, although the venom appears less toxic. While there is evidently a marked difference in the susceptibility of different persons to the effects of the sting, the general concern and excitement produced by 10 Department Circular 288, U. S. Dept. of Agriculture. the occurrence in great numbers of the caterpillars in some of the southern cities is sufficient evidence of the poisonous nature of the insect. In Dallas and other Texas cities hundreds and even thou- sands of cases of stings have occurred during a single season, and in some cases the fear of the caterpillars became almost a mania owing to the description of the effect of the stings which was passed from one to another. It is possible that the effects of stings may be Fig. 7.—Cocoon of puss caterpillar opened to show beveled cap or operculum. made more serious by the hysteria engendered by these often exag- gerated statements, especially if published in_ newspapers. In San Antonio, Tex., a few years ago the caterpillars became so abund- ant about some of the public schools, and the stings were so frequent, that the schools in question were ordered closed until all of the shade trees in the vicinity could be sprayed and this caterpillar brought under control. In Dallas and Fort Worth, Tex., and other cities the forestry departments were deluged with requests that something The Puss Caterpillar. 11 be done to eliminate the pest, and the street trees were sprayed with arsenicals on an extensive scale. It has been found that the long hairs on the caterpillars are harm- less, but the shorter spines which are hidden among them are respon- sible for the ill effects. Most of the stings are caused by inadver- tently pressing one of the caterpillars against an exposed part of the body. The severity of the sting seems to depend upon the tender- ness of the place struck and also the amount of pressure applied. As has been stated, the severity of the reactions varies much with the person. 3 Almost immediately after any portion of the body comes in contact with oneof these caterpillars an intense burning pain is felt, described bysome as similar to a severe nettlesting. Thisusually becomes worse accompanied by itching for several minutes and persists from 1 to 12 hours and sometimes longer. Almost immediately after a sting the area touched by the caterpil- lar shows minute raised whitish spots or papules which soon become red, followed by spreading of the inflammatory area for several inches and often accompanied by gen- eral swelling of the portion of the body stung. Stings on the wrist have been followed by a swelling of the entire arm to almost double its normal size. A feeling of numb- ness which almost assumes the characteristics of paralysis accom- panies the swelling. This is usually confined to the member attacked but may be generalized. Appar- ently stings on the neck are even worse, as the writer has one record of a man who was stung severely on the neck and completely incapa- citated, being confined to the hos- pital. for six days. These paralytic Fia. 8.—Ventral view of pupa of puss symptoms are often accompanied by oes nausea and sometimes by vomiting. The stings are especially severe among young children, who often develop considerable fever and nery- oussymptoms. These sometimes last for a day or two and are accom- panied by nausea, especially during the first few hours. Usually with- in two or three hours after a sting, the reddened pimple-like swellings at the site assume the appearance of small vesicles or blisters. These usually persist for a few hours and then apparently harden through absorption, leaving a roughened area. In some instances the discoloration of the skin surrounding the point of attack is rather marked, varying from a deep red to almost black. The paralytic symptoms usually subside with the pain, but the local lesions often persist for several days. While it is certain that the spines are the direct cause of the net- tling, it is rather difficult to explain the very severe symptoms, 12 Department Circular 288, U. S. Dept. of Agriculture. especially those of a generalized nature. It appears that when a caterpillar is pressed against the skin some of the spines, which are hollow, break off and others are pulled out. Beneath the clusters of spines apparently there are glands which secrete a poison which passes up within the spines, much as described by Packard in the related species Lagoa crispata Pack.* The poison glands of the brown-tail moth have been studied by Kephart * and investigations on the nature of the venom in that species have been carried out by Tyzzer.® NATURAL CONTROL. It is fortunate that, in Texas at least, some very effective natural control agencies are at hand. In fact it is difficult to rear larve to Fig 9.—Cocoon of puss caterpillar with exuvie protruding after emergence of moth. maturity on account of the high mortality among them due to a bacterial disease, usually manifesting itself among larve which are half grown or larger. They become sluggish and cease to feed. After a few days they die and become very soft, a typical result of bacterial infection. Specimens sent to Dr. G. F. White, of the Bureau of Entomology, were found to contain two distinct species of Micro- coccus, but he could not state positively that they were responsible for the mortality among the larve. In many instances this disease 8 Since this paper was prepared Dr. N.C. Foot has published some results of experiments with Megalopyge opercularis (Jour. Exp. Med., v. 35, p. 737-753, May 1, 1922). He found that injections into rabbits and mice of an extract of ground caterpillar skins and spines produced marked symptoms and even death. He concludes that, ‘The poison appears to be of the nature of a venom, combined with protein vehicles, and may beitselfa protein.”? It is rendered inert by boiling. 4 Packard, A. 8.