14 The Structure and Special Physiology of Insects 
Fig. 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 coeca, 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 coeca. 
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 
r Hatschek and Cori: twice 
fertilization takes place, r 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 coeca, 
then the true stomach, 
the thread-like Malpig¬ 
hian tubules, the bent 
intestine, and the ex¬ 
panded rectum. (After 
Snodgrass; enlarged.) 
