266 



MOTIONS OF INSECTS. 



Locusta given by Linne to the tribe to which it belongs. 1 

 All these insects have the terminal sncker between the claws, 

 three foot-cushions on the first joint of the tarsus, and one on 

 the second 2 ; and the same conformation also distinguishes 

 the feet of Truxalis. In the species of Acrydium F. ( Tetrix 

 Latr.), the foot-cushions, I believe — for in the dead insect 

 they are the reverse of conspicuous — are arranged nearly as 

 in the two preceding genera, but these insects are without the 

 claw-sucker. And lastly, Gryllus has neither suckers nor 

 cushions. From this statement it seems to follow — since 

 Blatta, Phasma, and Mantis, that do not leap, are provided 

 with cushions, and Gryllus, a heavy tribe of insects that does, 

 are without them — that their object cannot be exclusively to 

 break the fall of the insects that have them. And for the 

 same reason we may conclude that they must have some 

 further use than augmenting their elasticity when they jump. 

 When we consider that the Blattce, many of which have no 

 suckers, or very small ones, are climbing insects (I have seen 

 B. Germanica run up and down the walls of an apartment 

 with great agility), and that the long and gigantic apterous 

 spectres, &c. {Phasma) require considerable means to enable 

 them to climb the trees in which they feed, and to maintain 

 their station upon them, we may conclude that these cushions, 

 by acting in some degree as suckers, may promote these 

 ends. 



Amongst the homopterous Hemiptera, Chermes and many 

 of the Cercopidce 3 are furnished with the claw-suckers ; but 

 the noisy Cicada, as well as the heteropterous section, at 

 least as far as my examination of them has gone, have them 

 not. De Geer has observed, speaking of a small fly of this 

 order ( Thrips physapus), that the extremity of its feet is fur- 

 nished with a transparent membranaceous flexible process, 

 like a bladder. He further says that when the animal fixes 

 and presses this vesicle on the surface on which it walks, its 

 diameter is increased, and it sometimes appears concave, the 

 concavity being in proportion to the pressure ; which made 



1 See Zool. Jour, for 1825, No. iv. 431. 



2 Philos. Trans. 1816, t. xxi. f. 1—9. 



3 De Geer, iii. 132. 173. 



