318 MOTIONS OF INSECTS. 



strument which, when they are so circumstanced, ena- 

 bles them to spring into the air and recover their stand- 

 ing. If you examine the breast (pectus) of one of these 

 insects, you will observe between the base of the an- 

 terior pair of legs a short and rather blunt process, the 

 point of which is towards the anus. Opposite to this 

 point, and a little before the base of the intermediate 

 legs, you will discover in the after-breast (postpectus) 

 a rather deep cavity, in which the point is often sheathed. 

 This simple apparatus is all that the insect wants to 

 effect the above purpose. When laid upon its back, in 

 your hand if you please, it will first bend back, so as 

 to form a very obtuse angle with each otlier, the head 

 and trunk, and abdomen and metathorax, by which 

 motion the mucro is quite liberated from its sheath ; 

 and then bending them in a contrary direction, the 

 mucro enters it again, and the former attitude being 

 briskly and suddenly resumed, the mucro flies out with 

 a spring, and the insect rising, sometimes an inch or 

 two into the air, regains its legs and moves off. The 

 upper part of the body, by its pressure against the 

 plane of position, assists this motion, during which the 

 legs are kept close to its underside. Cuvier, when he 

 says that man and birds are the only animals that can 

 leap vertically % seems to have forgotten this leap of 

 Elaters, which is generally vertical, the trunk being 

 vertically above the organ that produces the leap. 



Other insects again leap by means of the abdomen or 

 some organs attached to it. An apterous species — be- 

 longing to the Ichneumonidce, and to the genus C7y- 

 ptusy F. — takes long leaps by first bending its abdomen 



* Anat. Comp. i. 498. 



