THE LOCUST OR SHORT-HORNED GRASSHOPPER ?.57 



between the body wall and the digestive tract and also in any 

 spaces within the appendages. The products of digestion pass 

 through the walls of the digestive tract into the blood and thence 

 by diffusion to all parts of the body, aided by the circulatory 

 mechanism and by the respiratoiy movements of the abdomen. 

 There are colorless cells, or leucocytes, within the blood, but no 

 colored cells comparable with the red corpuscles of vertebrates. 



The excretory system of 

 the locust, like those of the 

 majority of insects, consists 

 of the Malpighian tubules, 



which arise from the anterior </;<t?=:S=^^ .^^^^^^""^ )°vp. 



end of the intestine. In sec- 

 tion, such a tubule is seen 

 to be composed of large 

 excretory cells enclosed by 

 a peritoneum-like outer cov- 

 ering and surrounding a 

 cavity. The cuticular layer 

 that lines this cavity is per- 

 forated by canals and is con- 

 tinuous with the cuticle of 

 the intestine and thus with Fig. 180.— Sections of posterior end of 

 the external skeleton at the locust showing digestive and reproduc- 

 anal opening. The Malpighian ^^^'^ organs, 



tubules extend into the haemo- -'*■ ^"^^ f'^'"^''' '^''^ ovipositor? expanded. 



, . . . . B, the male, a, anus; a.g., accessory glands; 



COele. i neir CaVlvieS are in e^., ejaculatory duct; e.g., egg guide; od, ovi- 



COmmunication with the in- '^"^t: ""P- ovipositor; p. penis; r.. rectum; 



. •II *■''•• seminal receptable; v, vagina; v.d., vas 



testine but not with the deferens. (After Snodgrass, loc. cil.) 



haemococle. The relationship 



of their cells to the surrounding fluids is, therefore, not unlike 

 that of the cells in the kidney tubules of a vertebrate or the 

 nephridia of an earthworm. It is supposed that nitrogenous 

 wastes are taken from the fluid of the ha?mocoele and passed into 

 the cavit}'' of the intestine. The existence of this function is 

 further indicated by chemical tests which show the presence of 

 relatively large amounts of nitrogenous wastes in the Malpighian 

 tubules. In some insects the fat-body is in part concerned with 

 excretion, since it becomes a permanent storage place for nitrog- 

 enous compounds that are relatively insoluble. 



v.a... ! .\ 



a.g 



