INSECT A. 11 



to the head, and the inference is that this region is 

 composed of at least as many rings which have be- 

 come so firmly consolidated that the sutures are not 

 easily traced. It is seen that most of the sense organs 

 are placed at the forward end of the body, where they 

 are most useful in the search for food, and where 

 their concentration correlates with the concentration 

 of the nervous system into a brain.^ 



The three rings of the thorax each bear a pair of 

 legs. The first pair (PI. I., Fig. 3, /) is the shortest. 



The leg consists of five well-marked sections ; the coxa 

 (Fig. 3, /, ex), trochanter (/*<;), femur (/r), tibia {tb), and 

 tarsus or foot itr). The tarsus is made of three sections ; 

 the first two have soft cushions {cs) on the lower side, 

 while the third is slender, and bears at its end the pulvillus 

 (//), and two claws {fw). 



The second pair of legs (Fig. 3, /") is similar to the 

 first pair. The third pair (Fig. 3, /'") is more than 

 twice the length of the others. The femur (/'",/>'') 

 is club-shaped, and is greatly developed. The strong 

 leaping muscles contained in this section of the leg 

 are attached to the inner side of the skeleton, the 

 points of attachment being plainly marked by lines 

 which form a pretty pattern on the exterior. The 

 three pairs of legs are attached to the body at a dif- 

 ferent angle. The first pair (see PL I., Fig. 2, which 

 represents the locust ready to leap) extends forward, 

 while the second passes outward and backward, and 

 the third upward and backward : when the insect is 

 flying (PL L, Fig. i), the leaping-legs are straightened. 



i Worms and Crustacea, No. VII., p. 39. 



