462 MOTIONS OF INSECTS. 



cushions, I believe for in the dead insect they are the reverse of con- 

 spicuous 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 Blatta, many of which have no suckers, or very 

 small ones, are climbing insects (1 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 Cer- 

 copidce 1 are furnished with the claw-suckers : but the noisy Cicadce, 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 furnished 

 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 him suspect that it acted like a cupping-glass, and so produced the 

 adhesion. 2 This circumstance affords another proof that the foot-cushions 

 in the Orthoptera may act the same part ; they appear to be vesicular ; and 

 in numbers of specimens, after death, I have observed that they become 

 concave, particularly in Acrida viridissima. 



In Cimbex, and others amongst the saw-fly tribes, the claw-sucker is dis- 

 tinguished by this remarkable peculiarity, that its upper surface is con- 

 cave 3 , so that before it is used it must be bent inwards. Besides these, 

 at the extremity of each tarsal joint these animals are furnished with a 

 spoon-shaped sucker, which seems analogous to the cushions in the Gryl- 

 lina, Locustina, &c. ; and, what is more remarkable, the two spurs (calcarid) 

 at the apex of the shanks have likewise each a minute one. 4 Various 

 other insects of this order have the claw-suckers. Amongst others the 

 common wasp (Vespa vulgaris) is by these enabled to walk up and down 

 our glass windows. 



We learn from De Geer that several mites (to finish with the Aptera) 

 have something of this kind. Among these is the cheese-mite (Acarus 

 siro) -, its four fore feet being terminated by a vesicle with a long neck, to 

 which it can give every kind of inflexion. When it sets its foot down, it 

 enlarges and inflates it ; and when it lifts it up, it contracts it so that the 

 vesicle almost entirely disappears. This vesicle is between two claws. 5 

 The itch Acarus {A. scabiei) is similarly circumstanced. Ixodes Ricitius 

 \ 



1 De Geer, iii. 132. 173. 



2 Ibid. iii. 7. 3 Phibs. Trans. 1816, t. xix. f. 3, 4. 

 4 Philos. Trans. 1816. t. xix. f. 19. 



* De Geer, vii. 91. t. v. f. 6, 7. 



