INSECT A. 11 



hilar layer, the epidermis. ^ It is homologous with the 

 cuticle of the earthworm and the crust of the lobster, but 

 diifers from the latter in having no layers of calcareous 

 matter. It is entirely composed of tough, horny matter, 

 called chitine, which prevails in the Articulata ; i.e. Worms, 

 Crustacea, and Insects. The colors of the skeleton are 

 generally considered to be due to pigment in the epidermis 

 shining through the cuticula.^ They vary from reddish 

 brown to olive-green, passing from dark, rich shades above 

 to lighter tints below, as is the case in most deeply colored 

 animals. 



Upon looking at the body of the locust, one sees 

 that the integument exhibits a series of constrictions 

 dividing the body into rings, and these rings are 

 grouped into three regions separated by soft, pliable 

 membrane not stiffened by chitine. The anterior region 



1 Also called " hypodermis " by many entomologists,\vho speak 

 of the cuticle as the epidermis. This is a misuse of terms, the 

 true epidermis being a true cellular layer and never an excretory 

 product. 



2 Dr. Hagen {Proc. Amer. Acad., Vol. XVII., 1882, pp. 242- 

 245) says there are two kinds of colors: one belongs to the 

 cuticula, the other to the hypodermis. The colors of the cuticula 

 are persistent, while those of the hypodermis are not. 



Dr. Minot (" Zur Kenntniss der Insektenhaut." y^;r/«V. y?Vr 

 mikroskop. Anatotnie., Bd. XXVIII.) gives a few observations 

 on the structure of the outer cuticle, especially of caterpillars, 

 " In the larvye of many insects a part of the coloring is caused 

 by the pigmenting of the cuticle. The pigment may extend 

 through the whole cuticle, but is generally confined to the ex- 

 treme outermost layer, and is found there in connection with 

 peculiar modelings of the surface arranged in microscopic fig- 

 ures, which claim our interest not only on account of their ele- 

 gance, but also their variations, which are characteristic for each 

 species." 



