PSYCHE. ON SOME GLANDS WHICH OPEN EXTERNALLY ON INSECTS. BY GEORGE DIMMOCK, CAMBRIDGE, MASS. The following paper consists, for the yellow or red,-- contains the odorous most part, of compiled material 1)rought fluid. The red tubercl(!s are seen, in into connected form in consequence of sections cut with the microtome, to be ideas suggested to me in studying 0(101'- divided into compartments, the cavities iferous glands of the hrvae of Attacus of each spine opening into a compartment cecropia, to which I have already called at its basal end. :['he spines themselves the attention of the Calnbridge Entomo- are quite rigid and very brittle, so that logical Club, at its meeting of 13 Oct. they break away at a slight touch and 1882. Since that time I have made sec- leave a hole in the tubercle, out of which tions of the above-mentioned glands of the odorous fluid pours, pushed by inter- Attact.ts cecrol)ia, and of those which I hal pressure. This fluid, which I have found later in tile larvae of a pterophorid, not examined carefully, but which I hepe Aciptihts lobidcctylus; the glands of the later to study chemically, is strongly acid larvae of these two species have furnished to litmus paper, but causes a purple the original descriptive matter of this precipitate in carmin solutions. Larvae paper. of Attacus cecropia are provided with The peculiar odor of tile larvae of Atta- these glands and the odorous fluid as cus cecropia, when they are roughly han- early as the third la.rval stage--perhaps dled, has probably escaped the notice of earlier--and apparently shed the glands but few persons who have reared these in the tubercles when moulting the last moths through their larval stages. If a larval skin in order to enter the pupal larva be examined carefully the black state. spines upon its red, blue, and yellow The odor given out by the glands of knobs, o1: tubercles, will be seen to break the larvae of Attacus cecropic suggests at easily from the tubercle, and a clear yel- once their protective function, and, after low fluid of disagreeable odor to ooze having watched a sparrow (Passer domes- from each opening left by the injury. ticus) drag a sphingid larva about, seiz- By crushing the tubercle with a pair of ing it usually by the horn, it seemed forceps the same strong odor is very likely to me that the disagreeable acid noticeable, and by this mode of treat- fluid in the tubercles of the larva of ment one has no difficulty in proving that Attacus cecropia was a protection to the each tubercle, small or large,blue, larva fi'om similar rough treatment. 388 PS T'CHE. Having found these interesting glands American species.of lepidoptera which on the larvae of .Attacus cecropia, glands are known to sting. Lintner has experi- concerning which I can find no mention mented further upon the stinging power in entomological literature, my attention of the larvae of Lagoa crispata, and Miss was drawn further to the subject of exter- Murtfeldt upon that of the larva of naI glands of insects, many of wlfich are Lagoa opercularis. That the sting of protective or defensive in function. some of these larvae can do lasting in- Glands similar to those of tile larwt jury is certain, for my mother, when of Attacus ceero;pia, in that they have no twenty-seven years old, received so outlet until one is produced by external severe a sting in the middle finger of one agency, are not rare in the larvae of hand in brushing away a larva from her bombycidae. The severe poisoning pro- neck that tile distal joint, healing only duced by tile hairs of certain larvae of after several months, remains somewhat bombycidae, of which the so-called pro- stiffened and slightly deformed, now thir- cessionary caterpillar of Europe is an ty-seven years. For a time the stinging example and observed, according to of these bombycid larvae was attributed Moufet, by Dioscorides and other early to the action of the hairs in entering writers, is caused by tile secretion fi'om a and wandering about in tile flesh, and minute gland at the base of each hair. even as late as 1881, long after tile dis- The secretion of these glands fills the covery of the glands at the base of the hollow central portion of the hair, and hairs, Goossens advances the idea that when the sharp, often barbed, hairs are the poison of the proeessionary caterpil- broken in the flesh of attacking animals, lar of Europe comes from other glands the broken parts carry with them the which I shall mention more in detail poisonous secretion. This secretion is, later. Keller, in 1883, discusses the perhaps, formic acid or a formate in solu- mode of urtication in the processionary tion. Karsten, in 1848, described the caterpillars (larwxe of Gcstropacha) and anatomy of the poison glands at the base figures the glmds at the bases o' their of the hairs of an American species of hairs. Sturnia. Fine illustrations of this kind Still another tbrm of gland without of gland are to be found in the stinging any outlet until broken open, but a gland hairs of the larvae of Ityperchiria io and which can scarcel}" be classed witll those Hemileuca maia, both common insects previously mentioned, is that at the an- in parts of the United States. Lintner terior end of certai bombycid pupae, and Riley have recorded their experi- which breaks when the imago springs ments on the stinging power of these the chitinous pupal skin, and leaves its two species of larvae, and the latter secretion, which has been termed bomby- writer has given a list of the larvae of cic acid, on the head of the moth, the ltttter using the secretion to moisten tile 1For literature referred to throughout this paper threads of the cocoon so that they can the end of the article. PS 389 be cut or pushed aside to allow the es- Second are hairs (from 0.08 to 0.14 ram. cape of tbe imago within. I have never long) more or less dumb-bell or club studied this gland and will refer for fur- ibrmed which are filled with granular ther notice to tile easily accessible papers matter, and seem to be set usually only of Trouvelot, Packard McLaren1 and upon the surface of the chitinous cover- Worthington, wherein references can ing of the larva. Third are the longer be found to earlier European writers on hairs (from 0.8 to 1.3 mm. long) linear this subject. or slightly clavate usually burst at the It is an easy transition from the glands tip or sometimes along the sides, and of the larvae of Attacus, Hyperchiria where burst surrounded by a drop of and Hemileuca, closed by brittle hollow exuded gummy matter. These last hairs spines or hairs, to the glandular hairs are mounted by a kind of joint such as of certain larvae ofpterophoridae where is often present at the base of insect the hairs are apparently burst open at hairs, upon or near the summit of little their tips by the pressure of the secretion conical elevations which rise about 0.2 within them the liquid then oozing out mm. above the surface of tile dorsal and to tbrm a dew-like drop upon each hair. lateral parts of the larvae. These Zeller 1: mentions glandular hairs ('dr- hairs are arranged systematically and senh/irchen") on the larvae of Mimeseo- synmetridally upon the different seg- ptilus phaeodactylus and M. mictodactylus ments of the larva, tile most prominent but says nothing of the structure or use of them being a pair upon a conical of these hairs. Miss Murtfeldt writes elevation just at each side of the median of the larva of Leioptilus sericidactylus dorsal line of each segment. A com- 'Dorsal hairs proceeding fl'om prominent parison of the arrangement of these hairs tubercles and of two sizes in each tuft and prominences with the arrangement each of the shorter ones tipped with a of hairs and warts upon other lepido- minute pellucid bead of viscid fluid to pterous larvae, especially of those upon which pollen and bits of leaves often ad- the larvae of tortricidae would be an here." I have found the larva of Aci.pti- interesting study. The interior of hairs lus lobidactylus to be covered in like of this third form opens at the base into manner, with glandular hairs. the conical proninence or wart on which Upon making transverse sections of the hair is situated. The prominence is the larva of Aciptilus lobidactylus, its ex- probably entirely filled by the gland ternal surface is ibund to bear three which secretes the viscid matter that kinds of appendages. First are the very finds outlet through the hair. minute but obtuse spines (about 0.01 The specimens of the larva of which mm. long) which clothe most softer and I made microtomic sections were not more flexible portions of its external quite well enough preserved to admit of covering, and which are found on many carefully studying the gland at the bas larvae of difirent orders of insects. of the hairs. The hairs of the second 390 PS 2CttE. and third form seem to be modifications lobidactylus, reared from larvae taken of each other, for, in the longer and when nearly full-grown, while I have al- more clawtte hairs of the second form, ways obtained, in rearing a much less the granular matter in the hair extended number of Oxyptilus periscelidactylus without interruption into the larva, under similar conditions, several para- and these hairs often burst and give out sites.