328 THE MECHANICAL FUNCTIONS. 



of imperfection. As long as the insect remains 

 in its larva stage, its condition is analogous to 

 that of the myriapode : but in the more elevated 

 state of its existence, its structure is subject to 

 new conditions and regulated by new laws. 



While the number of members is thus reduced, 

 ample compensation is given by their increased 

 activity and power, derived from their augmented 

 length, and the more distinct lever-like forms of 

 the pieces which compose them. 



These pieces (see Fig. 150) are named, from 

 their supposed analogy to the divisions of the 

 limbs of the higher orders of vertebrated animals, 

 the haunch (H), the trochanter (T), the femur 

 (F), the tibia (s), and the tarsus (R). In general 

 the femur (or thigh) has nearly a horizontal, and 

 the tibia (or leg) a vertical position, while the 

 whole tarsus (or foot) is applied to the ground. 



The haunch (H), which is supposed to corres- 

 pond to the hip bone of quadrupeds, is a broad, 

 but very short truncated cone. The mode of its 

 articulation with the trunk admits of great variety ; 

 sometimes it is united by a ball and socket joint, 

 as in the Curculio and Cerambyx ; and it then 

 has, of course, great freedom of motion : at other 

 times the joint is of the hinge kind, as in the 

 Melolontha. The trochanter (T), and the femur 

 (F), though in reality distinct pieces, are usually 

 so firmly united as to compose only one division 

 of the limb. The articulation of this portion 



