296 MOTIONS OF INSECTS. 



at Reaumur's Memoir upon the enemies of caterpil- 

 lars, where I met with an account of a similar jumping 

 chrysalis, if not the same. Round the nests of the ca- 

 terpillar of the processionary moth, before noticed*, 

 he found numerous littje cocoons suspended by a thread 

 three or four inches long to a twig or a leaf, of a short- 

 ened oval form, and close texture, but so as the meshes 

 might be distinguished. These cocoons were rather 

 transparent, of a coifee-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 leap- 

 ing. 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 pro- 

 portioned to the force of the blow. At first sight this 

 faculty seems of no great use to an animal that is sus- 

 pended in the air ; but the winds may probably some- 

 times 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, for different cocoons gave different flies : 

 whence it was evident that these ichneumons were in- 

 fested by their own parasite b . This might be the case 



* VOL. I. 475; and above, p. 23. 

 b Reaum. ii. 450. 



