14 The Structure and Special Physiology ot Insects 



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



;:::::;v^,"'-''r*^;;'~^'' !M 



-Diagrammatic figures of bits of insect muscle, variously treated. 

 Gehuchten; greatly magnified.) 



(.■\fter Van 



Fic. 23. — Alimentary 

 canal of a lorust. At 

 upjwr cnrl the tcsoph- 

 agus, then the cx- 

 )>anded 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 

 Sncjdgras.s; enlarged.) 



contracted elsewhere to be oesophagus or intestine. 

 One or two pairs of salivary glands pour their tluid into 

 the mouth, while the digesting stomach or ventriculus 

 usually possesses two or more pairs of diverticula known 

 as gastric caca, 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 caxa. 



Two striking peculiarities 

 about the reproductive system 

 of insects are the possession 

 by the female of one or more 

 spermathecoe (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 ^ 

 ., • , 1- . Fig. 24. — Dissection of 



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

 hard shell, before its specific alimentary canal. (After 

 f .•c ,• , 1 1 r' Hatschek and Cori; twice 



fertilization takes place. Fer- natural size.) 



al.c. 



