28G MOTIONS OF INSECTS, 



{Cerura Vinula) and some others, instead of tlie anal 

 prolegs, have two tails or horns. A hemigeometer, de- 

 scribed bj^ Do Geer, has only six intennediate prolegs, 

 the posterior pair of which are longer than the rest, to 

 assist the anal pair in supporting the body in a posture 

 more or less erect*. Other hemigeometers, of which 

 kind is the larva of Flusia Gamma ^\ have only six pro- 

 legs, four intennediate and two anal. The true geome- 

 ters or surveyors {Geometrce) have only two intermediate 

 and two anal prolegs. Many grubs of Coleoptera, espe- 

 cially those oi'Sfaphi/lltiidcc, Silphidce, &c. which are long 

 and narrow, are furnished with a stiff joint at the anus, 

 which they bend downwards and use as a prop to pre- 

 vent their body from trailing. This joint, though with- 

 out claws, may be regarded as a kind of prolcg, which 

 supports them when they walk ^ ; and probably may as- 

 sist their motion by pushing against the plane of position. 



With respect to the larvae that have only perfect legs, 

 having just given you an account of these organs, I have 

 nothing more to state relating to their structure. I shall 

 therefore now consider the motions ofpedate larvae, un- 

 der the several heads of walking or running, jumping, 

 climbing, and swimming. 



Amongst those that "jsalk, some are remarkable for 

 the slowness of their motion, while others are extremely 

 swift. The caterpillar of the hawk-moth of the Fili- 

 pendula {Zygcena Filipcndulce) is of tiie former descrip- 

 tion, moving in the most leisurely manner; while that of 

 Apatela leporinOi a moth unknown in Britain, is named 

 after the hare, from its great speed. The caterpillar of 



' De Geer, i. 379. t. xxv./. 1. :?. " Voi.. I. 19xJ-. 



" De Goer, i. \2. 40. /. i. '/. 37. q- t. vi./ U.c. 



