THE LOCUST OR SHORT-HORNED GRASSHOPPER 345 



part of the body. The skeleton, like that of other arthropods, is 

 an external layer of firm 

 consistency, thinning out 

 at the joints and marked 

 off by grooves into the 

 so-called plates, but every- 

 where continuous over the 

 outer surface and con- 

 tinued within the anterior 

 and posterior ends of the 

 digestive tract as a deli- 

 cate cuticle. Unlike the 

 skeletons of many Crus- 

 tacea, that of the grass- 

 hopper and other insects 

 is not hardened with car- 

 bonate of lime but only 

 by additions of the chitin- 

 ous substance that is 

 characteristic of all arthro- 

 pod skeletons. The rela- 

 tionship between this 

 skeleton and the under- 

 lying epidermal cells, by 

 which it is secreted, is 

 similar to what has been 

 described for the crayfish 

 (c/. p. 325). Before the 

 molting (Fig. 169), a new 

 skeleton is secreted with- 

 out becoming united with 

 the older skeletal layer 

 within which it is enclosed. 

 The same principles of 

 skeletal relationships and 

 metameric organization 

 that have been indicated 

 for the Crustacea may, 

 therefore, be applied to 

 the locust. The animal consists of a series of somites which are 



Fig. 169. — ]\Iolting of locust. 



A, B, C, D, E, successive stages in process, 

 slightly enlarged. (After Riley. Reproduced from 

 Linville and Kelly, "General Zoology," copyright, 

 1906, by Ginn & Co., reprinted by permission.) 



