488 Mr. Blackwall on the Pulvilli of Insects. 



presumptuous ; nevertheless, as facts absolutely irreconcileable 

 with this supposition have been forced upon my attention, while 

 engaged in examining the evidence by which it is supported, I 

 shall, with every sentiment of respect for the high authorities 

 to whom I stand opposed, submit my views to the consideration 

 of candid and intelligent naturalists. 



Concerning the structure of the instruments by means of 

 which flies ascend the vertical sides of smooth bodies, various 

 opinions have been promulgated. Some authors compare them 

 to sponges, and conjecture that they are designed to contain a 

 glutinous secretion capable of adhering to well cleaned glass. 

 Dr. Hooke describes them as palms or soles beset underneath 

 with small bristles or tenters, like the wire teeth of a card for 

 working wool, which he conceived give them a strong hold upon 

 objects having irregular, or yielding surfaces ; and he imagined 

 that there is upon glass a kind of smoky substance penetrable 

 by the points of these bristles*. According to the observations 

 of Sir Everard Home, they are expanded membranes, having 

 their inferior surface granulated, and their edges beautifully 

 serrated -f-; while Messrs. Kirby and Spence, on the contrary, 

 remark that they are downy on the underside and granulated 

 above :]:. 



The want of accordance so conspicuous in the preceding ac- 

 counts induced me to inspect the parts minutely under a good 

 compound microscope, when it was immediately perceived that 

 the function ascribed to them by Dr. Derham and Sir E. Home 

 is quite incompatible with their organization. Minute hairs, 

 very closely set and directed downward, so completely cover the 

 inferior surface of the expanded membranes, improperly deno- 



* Micrographia,p. 170-171. 



■f Transactions of the Ro?/al Society for 1816, p. 323. 



X Introduction to Entomology, vol. ii.. Letter xxill. 



minated 



