332 THE MECHANICAL FUNCTIONS. 



dense velvetty tufts of hair, lining the underside 

 of the tarsi, but leaving the claw uncovered ; and 

 the filaments, by insinuating themselves among 

 the irregularities of the surfaces to which they 

 are applied, produce a considerable degree of 

 adhesion. Cushions are met with chiefly in large 

 insects which suddenly alight on the ground 

 after having leaped from a considerable height : 

 in the smaller species they appear to be unne- 

 cessary, because the lightness of their bodies 

 sufficiently secures them from any danger arising 

 from falls. 



Some insects are furnished with a still more 

 refined and effectual apparatus for adhesion, and 

 one which even enables them to suspend them- 

 selves in an inverted position from the under 

 surfaces of bodies. It consists of suckers, the 

 arrangement and construction of which are ex- 

 ceedingly beautiful ; and of which the common 

 house-fly presents us with an example. In this 

 insect that part of the last joint of the tarsus 

 which is immediately under the root of the claw, 

 has two suckers appended to it by a narrow 

 funnel-shaped neck, moveable by muscles in all 

 directions. These suckers are shown in Fig. 

 152, which represents the under side of the foot 

 of Musca vomitoria, or blue-bottle fly, with the 

 suckers expanded. The sucking part of the 

 apparatus consists of a membrane, capable of 

 contraction and extension, and the edges of 



