MOTIONS OF INSECTS. 445 



this history, I happened to have occasion to look at Reaumur's memoir 

 upon the enemies of caterpillars, where I met with an account of a similar 

 jumping chrysalis, if not the same. Round the nests of the caterpillar of 

 the processionary moth, before noticed, he found numerous little cocoons 

 suspended by a thread three or four inches long to a twig or a leaf, of a 

 shortened oval form, and close texture, but so as the meshes might be dis- 

 tinguished. These cocoons were rather transparent, of a coffee-brown 

 colour, and surrounded in the middle by a whitish band. When put into 

 boxes or glasses, or laid on the hand, they surprised him by leaping. 

 Sometimes their leaps were not more than ten lines, at others they were 

 extended to three or four inches, both in height and length. When the 

 animal leaps, it suddenly changes its ordinary posture (in which the back 

 is convex and touches the upper part of the cocoon, and the head and anus 

 rest upon the lower), and strikes the upper part with the head and tail, 

 before its belly, which then becomes the convex part, touches the bottom. 

 This occasions the cocoon to rise in the air to a height proportioned to the 

 force of the blow. At first sight this faculty seems of no great use to an 

 animal that is suspended in the air ; but the winds may probably sometimes 

 place it in a different and unsuitable position, and lodge it upon a leaf or 

 twig : in this case it has it in its power to recover its natural station. 

 Reaumur could not ascertain the fly that should legitimately come from 

 this cocoon 1 , for different cocoons gave different flies : whence it was evi- 

 dent that these ichneumons were infested by their own parasite. 3 This 

 might be the case with that of the lady just mentioned. Perhaps, properly 

 speaking, in this last instance the motions ought rather to be regarded as 

 belonging to a larva; but as it had ceased feeding, and had enclosed itself 

 in its cocoon, I consider it as belonging to the present head. 



You may probably here feel some curiosity to be informed how the 

 numerous larvae that are buried in their pupa state, either in the heart of 

 trees, under the earth, or in the waters, effect their escape from their various 

 prisons and become denizens of the air, especially as you are aware that 

 each is shrouded in a winding-sheet and cased in a coffin. In most, how- 

 ever, if you examine this coffin closely, you will see RESURGAM written 

 upon it. What I mean is this. The puparium, or case of the animal, is 

 furnished with certain acute points (adminicula), generally single, but in 

 some instances forked, looking towards the anus, and usually placed upon 

 transverse ridges on the back of the abdomen, but sometimes arming the 

 sides or the margins of the segments. By this simple contrivance, aided 

 by new-born vigour, when the time for its great change is arrived, the 

 included prisoner of hope, if under ground, pushes itself gradually upwards, 

 till reaching the surface its head and trunk emerge, when an opening in the 

 latter being effected by its efforts, it escapes from its confinement, and once 

 more tastes the sweets of liberty and the joys of life. Those that are in- 

 closed in trees and spin a cocoon, are furnished with points on the head, 

 with which they make an opening in the cocoon. The pupa of the great 

 goat-moth (Cossus ligniperda) thus, by divers movements, keeps disengaging 

 itself from this envelope, till it arrives at a hole in the tree which it had 

 made when a caterpillar; when its anterior part having emerged, it stops 



1 Mr. Westwood states that it belongs to the genus Perilitus, belonging to the 

 Ichneumonidje. See Mod. Class. Ins. ii. p. 149. for further notices upon it. 



2 Reaum. ii. 450. 



