STRUCTURE OF INSECTS. 



235 



Many insects are provided with cushions at the extremity 

 of the feet, evidently for the purpose of breaking the force 

 of falls, and preventing the jar which the frame would other- 

 wise have to sustain. These cushions arc formed of dense 

 velvety tufts of hair, lining the underside of the tarsi, but 

 leaving the claw uncovered; and the filaments, by insinuat- 

 ing themselves among the irregularities of the surfaces to 

 which they are applied, produce a considerable degree of ad- 

 hesion. 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 ap- 

 pear to be unnecessary, 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 themselves in an inverted position from the 

 under surfaces of the bodies. It consists of suckers, the ar- 

 rangement and construction of which are exceedingly beau- 

 tiful; 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 tbe 

 foot oiMusca 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 which are serrated, so as to fit them for the closest 

 application to any kind of surface. In the Tahcmiis, or 



horse-fly, each foot is furnished with three suckers. In 

 the Cimbex hUea, or yellow saw-fly, there are four, of which 



