STRUCTURE OF INSECTS. 67 



ments are closely united, but the natural distinction be- 

 tween them is marked by a transverse line. 



The third principal division is the abdomen, Fig. 53. 

 Fig. 53. This, in the instance before us, is com- 



posed of six complete, and three im- 

 perfect segments, but these segments 

 vary in number in different insects 

 from three or four, to twelve or more. 

 These segments all have a ligamentous 

 connection with each other, allowing 

 free motion in all directions. 



The limbs of Insects, are named 

 from their supposed analogy to cor- 

 responding parts in the higher order of animals. Thus the 

 haunch, h, corresponds to the hip bone of quadrupeds ; 

 the trochanter, t, to the head of the thigh bone ; the 

 femur, /, to the thigh bone itself ; the tibia, s, to the 

 bones of the leg ; and the tarsus, r, to those of the foot. 

 It is perhaps unnecessary in a work like the present, 

 to give a detailed account of the peculiar mechanism, 

 motions and uses of each of these parts. The limbs of 

 Insects down to the feet, may be considered as acting in 

 a manner analagous to our own. The feet have pecu- 

 liarities to which there is no analogy in other animals, 

 and which therefore must receive further notice. 



The legs of most Insects diverge, so as to reach con- 

 siderably beyond their bodies on each side, thus giving 

 them a firmer support, by throwing the centre of grav- 

 ity far within the base. When the legs are very long, 

 the Insect therefore, appears rather suspended, than sup- 

 ported by them, contrary to what obtains in quadrupeds 

 and man, where the feet are immediately below the 

 points where the legs are connected with the body. 



In Insects, the last joint of the tarsus is generally ter- 

 minated by a claw, sometimes single, and sometimes 

 double, and by which the foot is fastened in walking to 

 any surface which is in the least degree rough, or un- 

 equal. By these hooks insects also suspend themselves 

 on perpendicular surfaces, or with their backs down- 

 wards, this being from the mechanism of these parts, the 



By what means do insects walk on rough surfaces ? 



