MOTIONS OF INSECTS. 327 



reus section, at least as far as my examination of them 

 has gone, have them not. De Geer has observed, speak- 

 ing of a small fly of this oicler {Thrips Phijsapus), that 

 the extremity of its feet is lurnished 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 con- 

 cavity being in proportion to the pressure ; which made 

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

 produced the adhesion^. This circumstance affords 

 another proof that the foot-cushions in the Ortlioptera 

 may act the same part ; they appear to be vesicular ; 

 and in numbers of specimens, after death, I have ob- 

 served that they become concave, particularly in Acrida 

 vhHdissima. 



In Cimbex, and others amongst the saw-fly tribes, the 

 claw-sucker is distinguished by this remarkable pecu- 

 liarity, that its upper surface is concave '', so that before 

 it is used it must be bent inwards. Besides these, at 

 the extremity of each tarsal joint these animals are fur- 

 nished with a spoon-shaped sucker, which seems analo- 

 gous to the cushions in the Gryllina, Locustijia, &c.: and, 

 what is more remarkable, the two spurs {calcaria) at the 

 apex of the shanks have likewise each a minute one ^. — 

 Various other insects of this order have the claw-suck- 

 ers. Amongst others the common wasp [Vesjpa tmlga- 

 ris) is by these enabled to walk up and down our glass 

 windows. 



We learn from De Geer that several mites, to finish 



" De Geer, iii. 7. " Philos. Trans. ]816. /. xix./. 3, i. 



' Ibid. L xix./. l-'J. 



