A STUDY OF THE GRASSHOPPER 15 



is composed of a series of more or less similar body rings or 

 segments. 



The Body-wall. Some parts of the skin or outer body- 

 wall are quite firm and horny in texture, others are more 

 parchment-like, and there are still other places in it, such as the 

 neck and between the segments of the legs, and the segments 

 of the abdomen, where the skin is soft and flexible. These 

 differences are due to the fact that a horny substance called 

 chitin is abundantly deposited in parts of the skin thus 



antennae 



compound 

 pronotum 



femuv 



tibia''' 



tarsal segments 



FIG. 5. The red-legged locust, Mdanoplus fcmur-rubnim, to show exter- 

 nal structure. 



making it firm for the protection of the internal organs, and 

 for the attachment of muscles. Wherever motion or the bend- 

 ing of the body-wall is desirable, little or no chitin is deposited. 

 The chitinized portions of a segment are called sclerites. The 

 furrows or lines between the sclerites are called sutures. 



The Head. Although the head is apparently a single seg- 

 ment, it is really composed of several body segments greatly 

 modified and firmly fused together, making a strong box which 

 contains what may, by analogy, be called the brain, and certain 

 other important organs. On each side of the head are the large 



