IKSECTS : THEIR FEET. 115 



the appearance of adhering to the glass by a viscid material 

 than by any pressure of the atmosphere ; and it is so far 

 in favour of Mr. Black wall's hypothesis, on which one 

 might conjecture that from some cause (perhaps of disease) 

 the hairs of the pul villi had poured out a greater quantity 

 of this viscid material than usual, and more than the 

 muscular strength of the fly was able to cope with."* 



In the foot of the fly under our own observation, you 

 may see how well the joints of the tarsus are covered 

 with hairs, or rather stiff pointed spines, of various di- 

 mensions and distances apart, and hence how suitable these 

 are for acting the part of combs to cleanse the palms. But 

 these last are the organs that most claim and deserve our 

 examination. In the specimen of the little Musca that 

 I have imprisoned, the last tarsal joint is terminated by 

 two strong divergent hooks which are themselves well, 

 clothed with spines, and by two membranous flaps or 

 palms beneath them. These are nearly oval in outline, 

 though in some species they are nearly square, or triangular, 

 and in some of a very irregular shape. They are thin, 

 membranous, and transparent, and when a strong light 

 is reflected through them, we see their structure under 

 this power of GOO diameters very distinctly. 



The inferior surface of the palm, on which we are now 

 looking, is divided into a vast number of lozenge-shaped 

 areas, which appear to be scales overlapping each other, 

 or they may be divided merely by depressed lines. From, 

 the centre of each area proceeds a very slender, soft, and. 

 flexible pellucid filament, which reaches downwards to the 

 surface on which the fly is walking, and is there slightly 

 hooked, and enlarged into a minute fleshy bulb. Those 

 from the areas near and at the margins of the palms more 

 and more arch outwards, so that the space covered by 

 the bulbs of the filaments is considerably greater than 

 that of the palm itself. 



* " In trod, to Entom.," 7th Ed., 458. 

 i 2 



