TERRESTRIAL LAKVVE. 313 



bending of a bow. By an artifice of the same 

 kind, some larvEe contrive to leap to a consider- 

 able distance, by the violent effort which they 

 make in unfolding the curvatures of their bodies. 



Some larvae avail themselves of their jaws in 

 order to fix the head, and drag the rest of the 

 body towards it. In this manner do the larvae 

 of the Capricorn beetles advance along the wind- 

 ing passages which they have themselves exca- 

 vated, holding by the jaws, and dragging them- 

 selves forwards. These movements are assisted 

 by the resistance afforded by short tubercles 

 which project from different parts of the back 

 and under surface of the body ; so that these 

 insects advance in the passage by an act similar 

 to that by which a chimney-sweeper, exerting 

 the powerful pressure of his elbows, shoulders, 

 and knees, manages to climb up a chimney. 



For the purpose of enabling insects to take 

 stronger hold of the surfaces they pass over, we 

 often observe them furnished with spines, or 

 hooks, which are moved by appropriate muscles, 

 and they occupy different situations on the body. 

 Modifications without end occur with regard to 

 these and other external parts subservient, in 

 various degrees, to progressive motion. Every 

 possible gradation is also seen between the short 

 tubercles already mentioned, and the more re- 

 gularly formed feet or legs. Those which are 

 regarded as spurious legs, or prolegs, as they 

 have been called, occupy an intermediate place 



