2 ANIMAL BIOLOGY 



own body. Like ourselves, however, it can walk, jump, 

 eat, breathe, see, hear, smell, make sounds and perform a 

 great number of other activities which show that it is not 

 so different from a human being as we might at first be 

 disposed to believe. 



In order to understand how these activities are carried 

 on it is necessary to study briefly the grasshopper's struc- 

 ture. The skeleton of the grasshopper's body is on the 

 outside, instead of on the inside as in ourselves, and it is 

 composed of a substance called chitin, which is thickened 

 in some regions where it has acquired a certain rigidity. 

 Externally the body shows a division into rings marking 



Prosteritdl 6 fin 



FIG. i. Side view of a typical grasshopper. (After Woodworth.) 



the individual segments of which the body is built up. 

 Some of the segments can move one upon the other. 

 In these cases the chitin between the segments is thinner 

 than elsewhere so as to become flexible, thus allowing 

 freedom of movement. In other cases the segments are 

 so closely united that there is no motion between them. 

 The body of the grasshopper shows a division into three 

 parts, the head, thorax and abdomen. Look with a hand 

 lens at the large eyes at the sides of the head and you may 

 see that they present a finely checkered appearance due 

 to their being composed of smaller elements. The grass- 

 hopper's eye is compound, and when we look at the trans- 



