26 



HABITS OF BIRDS. 



Grub of the Glow-worm devouring a Snail. 



culiar structure of the foot of flies (Diptera) con- 

 sidered as an instrument for cleaning, particularly as 

 it does not seem to be noticed in books of natural 

 history, though most people may have remarked flies 

 to be ever and anon brushing their feet upon one 

 another to rub off the dust, and equally assiduous in 

 cleaning their eyes, head, and corselet with their fore 

 legs, while they brush their wings with their hind 

 legs. In the foot of the common blow-fly (Musca 

 carnaria) there are two rounded combs, the inner 

 surface of which is covered with down, forming a 

 fine brush; and some crane flies (Tipulidce) have 

 three such combs on each foot, as may be seen in a 

 drawing of them which we have given elsewhere 

 for a different purpose*. 



* Insect Transformations, p, 391. 



