MOTIONS OF INSECTS. 327 



rous 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 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 con- 

 cavity being in proportion to the pressure ; which made 

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

 produced the adhesion 1 . 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 ob- 

 served that they become concave, particularly in Acrida 

 viridissima. 



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 b , 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^ Locustina, &c. : and, 

 what is more remarkable, the two spurs (calcarid) at the 

 apex of the shanks have likewise each a minute one c . 

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

 ers. Amongst others the common wasp (Vespa vulga- 

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

 windows. 



We learn from De Geer that several mites, to finish 



a De Geer, iii. 7. b PMos. Trans. 1816. t. xix./ 3, 4. 



e Ibid. /. xix./. 1-9. 



