14 The Structure and Special Physiology of Insects 



This tube is expanded variously to form crop, gizzard, or stomach, and 



FlG. 22. Diagrammatic figures of bits of insect muscle, variously treated. (After Van 

 Gehuchten; greatly magnified.) 



contracted elsewhere to be oesophagus or intestine. 

 One or two pairs of salivary glands pour their fluid into 

 the mouth, while the digesting stomach or ventriculus 

 usually possesses two or more pairs of diverticula known 

 as gastric cceca, which are lined with glands believed 

 to secrete special digestive fluids. Neither liver 

 nor kidneys are present in the insect body, but the 

 secretory function of the latter are undertaken by a 

 number of usually long thread-like tubular diverticula 

 of the intestine known as Malpighian tubules. The 

 intestine itself is usually obviously made up of three 

 successive parts, a large intestine, small intestine, 

 and rectum. There are also 

 present not infrequently in- 

 testinal cceca. 



Two striking peculiarities 

 about the reproductive system 

 of insects are the possession 

 by the female of one or more 

 spermathecae (Fig. 66, r.s.) in 

 which the male fertilizing 

 cells, the spermatozoa, are re- 

 ceived and held, and the com- 

 pletion of all the envelopes of 



FIG. 24. Dissection of 



the egg, including the outer cockroach to show (al.c.) 



hard shell, before its specific alimentary canal. (After 



, Hatschek and Con; twice 



fertilization takes place. J^er- natural size.) 



FIG. 23. Alimentary 

 canal of a locust. At 

 upper end the oesoph- 

 agus, then the ex- 

 panded crop, then sev- 

 eral large gastric cceca, 

 then the true stomach, 

 the thread-like Malpig- 

 hian tubules, the bent 

 intestine, and the ex- 

 panded rectum. (After 

 Snodgrass; enlarged.) 



al.c. 



