74 



COCOON. 



which, nevertheless, permits the inclosed chrysalis to 

 be seen through the small meshes. This cocoon is 

 moreover defended, by being formed in the middle 

 of a bunch of leaves ; and here it is interesting to 

 notice, that those caterpillars which are furnished 

 with a short supply of silk, are nevertheless very 

 anxious to conceal their slight cocoon in the 

 most effectual manner, by attaching together with 

 silken cords the adjacent leaves ; sometimes two or 

 three being drawn together, so as to meet at the 

 edges, and sometimes a single leaf being pulled out of 

 its natural position, so as to form a complete covering 

 to the cocoon. Sometimes, moreover, several cater- 

 pillars unite together, so as by their combined strength 

 to secure several leaves more firmly together, within 

 which they then, in company, undergo their transfor- 

 mations. Even many caterpillars, which spin a very 

 compact cocoon, resort to the same kind of manoeuvre, 

 rather, we should presume, as a means of support than 

 of defence. Other curious means are adopted by some 

 larvae, for the purpose of rendering their slightly 

 formed cocoons more opaque ; thus by some a kind of 

 paste-like matter is secreted from the anus, which, 

 being applied by the head upon the entire inner sur- 

 face of the cocoon, hardens and forms a powder, 

 which completely answers the intended purpose ; it 

 is probably a similar secretion which gives to the 

 chrysalides of the Catocalce the fine purple bloom, 

 which we have mentioned in our account of that 

 genus. Others^ again, as the caterpillars of the gar- 

 den tiger moths, rub off the hairs from their bodies, 

 with which they are so plentifully supplied, that they 

 have obtained the ordinary names of woolly bears, 

 and spin them into the substance of the cocoon in a 

 very ingenious manner, so as not to permit the ends 

 of the hairs to stand upright in the inside of the 

 case, which would, of course, fret the newly disclosed 

 chrysalis. 



The more perfectly constructed cocoons, however, 

 such, for instance, as that of the silk-worm, consist 

 apparently of two distinct portions, externally a loose 

 gauze-like covering, and internally a closely woven 

 and compact ball of an oval form. As the insect 

 works from the out to the inside of its case, the 

 former is of course first spun, but the whole is formed 

 of a single thread, disposed in two different ways ; 

 and here may be noticed the interesting circumstance, 

 that although the threads of these cocoons are fas- 

 tened together with gum, they are yet so slightly 

 adherent, that they may be easily unwound ; if their 

 union were more perfect it would be impossible to 

 divide the thread, which is as easily unwound as that 

 of a ball of cotton, but it is one of the essential quali- 

 ties of the gummy matter with which the thread is 

 coated, that it dries very quickly, so that no sooner 

 is it emitted from the spinnerets, than it is almost dry, 

 before it reaches the layer of threads upon which it 

 is about to be placed. According to Malpighi, six 

 distinct layers of silk are distinguishable in the cocoon 

 of the silk-worm, but Reaumur suspects there is often 

 a greater number ; be this however as it may, a single 

 thread may be unwound from it more than a thousand 

 feet long. 



Many interesting instances of the manufacture of 

 rarious kind of cocoons, not only composed of silk, 

 but also of silk and other materials, as leaves, moss, 

 earth, &c., are detailed by Reaumur and De Geer, 

 and which are introduced into the " Introduction to 

 Entomology.' and the " Insect Architecture." We 



trust, therefore, that our readers will feel more 

 interested in the two following instances, to which, 

 together with the account of the proceedings of the 

 Sombyx Promethea (see vol. i. j). 748), we shall 

 confine our notice of this branch of the subject, pre- 

 mising only, that much remains to be discovered, and 

 that a wide field of interesting inquiry is open, for 

 the investigation of those who prefer looking at the 

 workings of nature, to the mere getting together of a 

 collection of specimens. 



The first of these instances is recorded by Lyonnet 

 in his posthumous researches lately published, and re- 

 lates to the Tinea scqueUa of Fabrichis, a very small 

 moth, having the upper wings of a white satiny ground, 

 from the base to the middle, with darker markings 

 formed of small scattered black dots. Its caterpillar 

 is extremely small, not exceeding one-sixth of an inch 

 in length, and is found on the under-side of oak leaves. 

 Lyonnet, who had observed the proceedings of many 

 caterpillars in forming their cocoons, nevertheless 

 says of this, that it "emploie une addresse incon- 

 cevable" in forming its case, which is of a white 

 colour, and of a long oval form, having its upper 

 surface ornamented with seven upright ridges. Unlike 

 most cocoons, however, it is applied along the under 

 side to the leaf upon which it is placed, so that it 

 forms only an arc of a circle. The first step taken 

 by the larva is to erect about a score of small upright 

 silken palisades, arranged in an oval position all 

 round its body ; these are in no ways employed in 

 the construction of the cocoon itself, and seem only 

 to be erected to defend the larva whilst working. 

 Near to one end of this inclosure, the larva now 

 commences its cocoon in the manner represented in 

 the following figure. 



,l> LLLLL k 



L- ^ttlSfSsc H^fei^S^^. I 



The mode in which the ridges of this cocoon are 

 formed with perfect regularity, is indeed inconceiv- 

 able. Some idea may however be obtained of it from 

 the twa following figures. 



Here M, i, E, represent three longitudinal ridget, 

 and MI, IE, the intermediate space; the caterpillar 

 commencing at E, extends a thread to H, from H to i 

 forming an angle, from i it then proceeds to K, and 

 from K to H, forming another acute angle, and then 

 from H to T, and T to i, forming another obtuse 

 angle. It then proceeds in the same manner from I 



