BUTTERFLY. 



653 



The proceedings of the caterpillar are, however, of 

 the most simple kind. It first proceeds to form a 

 small conical mass of silken threads, which it spins 

 from the mouth ; this mass, however, instead of being 

 smooth and entire, is loose, and but slightly woven 

 together. It now proceeds to seize hold of this button 

 of silk with its hind pair of legs, which instead of 

 terminating in a single claw like the six fore legs, 

 are, as well as all the four other posterior pairs, 

 armed with a vast number of very minute curved 

 hooks, which therefore are well fitted to seize the 

 loose threads of the silk button previously formed. 

 When this is effected and the legs firmly fixed, the 

 fore legs of the insect quit their hold, its body falls 

 in a vertical direction, and the larva appears to be 

 suspended by the tail, the hind legs being placed 

 at the extremity of the body. 



Shortly afterwards, however, it raises its head a 

 little, which gives a curve to its back, and this motion 

 is repeated until a slit is made behind the head, and 

 which is increased by degrees along the back, until 

 the insect is enabled to extricate by muscular con- 

 traction the anterior part of its chrysalis form from 

 within the skin of the latter. Now this lower part is 

 broader than the upper, which gradually decreases in 

 size, so that the exuvia easily slides upwards towards the 

 tail, the chrysalis alternately extending and contract- 

 ing its body. This alone would be sufficient to cause 

 the exuvia to mount towards the attached legs, but its 

 movement is favoured by the angular projections of 

 the body of the pupa, which, as they point towards 

 the tail, prevent the skin from slipping down again; 

 they are, in fact, cogs acting like the cog-wheels of 

 our machinery. By degrees, therefore, the old skin 

 of the larva is pushed upwards, until its folds are 

 pressed together into a very small space, and it 

 appears like a small bristly mass surrounding the tail 

 of the chrysalis. The situation of the insect has 

 now become critical, since, notwithstanding its tender 

 state, it has three steps still to take, each of which 

 seems pregnant with danger. First, the chysalis is 

 compelled to suspend itself for a time to the insecure, 

 yet still attached, shrivelled skin of the larva : 

 secondly, it is necessary for it to withdraw itself even 

 from this support, and to attach itself to the silken 

 mass ; and thirdly, it has to rid itself of the mass of 

 exuvia, which would not only embarrass, but also hurt 

 it. from its spiny state. The first step is effected by 

 the pliability of the terminal rings of the body, by 

 which, being attached together by membrane, the 

 insect is enabled to form a kind of pliers, so as to 

 seize a part of the exuviae, whereby a resting place 

 is obtained, which enables it to withdraw the extre- 

 mity of its body from within the skin. Still the most 

 dilticult part of the process remains to be performed ; 

 retaining- hold, therefore, of the shrivelled skin, it is 

 enabled, by the elongation of the same membranous 

 connexion of the segments, to extend its tail upwards, 

 and, by the assistance of various minute hooks at the 

 extremity of the body, to attach itself to the little 

 mass of silk. This is indeed so delicate and perilous 

 a step, that the insect, even after redoubled efforts, 

 has sometimes been unable to hook itself in this 

 manner, and has consequently fallen to the ground. 

 This, however, only takes place with those which 

 having been stirred during the first part of the pro- 

 cess, have not spun a sufficiently large button of silk. 

 In a natural state, this of course does not occur ; and 

 we can scarcely avoid wondering how an animal, 



which performs this intricate manoeuvre but once in 

 the course of its life, should do it so perfectly. " On 

 en conclut," adds Reaumur, " necessairement qu'il a 

 ete instruit par un grand Maitre." Having, however, 

 attached itself by the tail, it proceeds to get rid of the 

 shrivelled skin of the larva, by first bending the ter- 

 minal portion of body into the form of the letter S, 

 and then giving the whole a sudden jerk, causes both 

 its body and the slough to spin round eighteen or 

 twenty times ; as, however, the latter is further 

 removed from the centre of gyration than the extre- 

 mity of the body, it is evident that the attaching 

 threads of the slough must suffer a greater strain than 

 those of the chrysalis ; consequently, the fonder, or 

 more probably, the hooks of the legs, give way first. 

 This is no sooner perceived by the chrysalis than it 

 resumes its vertical position, and the skin drops. If, 

 however, the first series of pirouettes does not prove 

 successful, another in the opposite direction is tried ; 

 but if, after repeated efforts, it is unable to tear off the 

 slough, it quietly submits to an evil which it cannot 

 remove. 



Such are the steps pursued by the caterpillars of a 

 great number of butterflies, including, amongst the 

 English species, the tortoise-shell, red and white 

 admiral, the frittillaries, Camberwell beauty, purple 

 emperor, &c., all of which are pre-eminently distin- 

 guished by their powerful flight and splendour of 

 colouring, and which form the family of Nymphatidce ; 

 but most of the other butterflies forming the families 

 Papilionidee, or true-tailed butterflies, white butter- 

 flies, &c., Lyc&nidce, or the blues and copper butter- 

 flies, not only attach themselves by the tail to the 

 steins of plants, &c., but the caterpillar fastens a skein 

 of silk across the middle of the body previous to 

 assuming the chrysalis state. The mode in which 

 this is spun from one side of the body to the other 

 (being attached on each side to a small mound of silk), 

 differs in different species ; some having a flexible 

 body, merely throwing the head of the caterpillar 

 over the back, and passing it repeatedly from side to 

 side until the skein is sufficiently strong ; whilst 

 others, having a body less pliable than the preceding, 

 adopt a method somewhat similar to that by which a 

 skein of silk is wound upon the hand the caterpillar 

 first attaching a thread on one side of the body, and 

 then carrying it over to the opposite side, forming a 

 loop about twice the size of the body by holding the 

 threads open with the assistance of its fore legs. 

 Sometimes, however, notwithstanding all the care of 

 the caterpillar, the threads will slip off its legs, where- 

 upon it endeavours.with surprising patience, to replace 

 them ; but, notwithstanding every contortion, some- 

 times in vain. 



Unlike the caterpillars of some species of moths, 

 those of very few butterflies have been ascertained to 

 be social ; examples of the spirit of sociability, how- 

 ever, occur in the peacock and tortoise-shell upon 

 nettles, and also in one of the frittillaries upon the 

 plantain, but their nests are of very slight texture. 

 The most perfect instance of sociality amongst butter- 

 flies is recorded in the first number of the Trans- 

 actions of the Entomological Society just published, 

 in the case of a gregarious nest-making butterfly 

 found in Mexico. Mr. Hardy, who also appears to 

 have noticed this species, describes the nests as being 

 inclosed apparently in white paper bags, in the 

 manner of grapes in England, to preserve them from 

 birds and flies. He had the curiosity to examine one 



