I20 EN TOMOLOGY 
stomach, however, is absorption, which is effected by the 
general epithelium. Physiologically, the so-called stomach of 
an insect is quite unlike the stomach of a vertebrate, being more 
like an intestine. 
Proctodzum.—At the anterior end of the hind intestine 
there is usually a pyloric valve, which prevents the contents of 
the intestine from returning into the stomach. This valve may 
operate by means of a sphincter, or constricting, muscle, or 
may, as in Collembola (Fig. 144), con- 
sist of a backward-projecting circular 
ridge, or lip, which closes upon pressure 
afi 
een 
-S from behind. 
In its primitive condition the hind 
ron 
Py 
ra 
e' 
of 
intestine is a simple tube (Fig. 144). 
Usually, however, it presents two or 
even three specialized regions, namely 
and in order, iewm, colon and rectum 
(Fig. 145). The hind intestine varies 
greatly in length and is frequently so 
long as to be thrown into convolutions 
(Fig. 150). The ileum is short and 
stout in grasshoppers (Fig. 145) ; long, 
slender and convoluted in many carniv- 
orous beetles; and quite short in cater- 
Digestive system of Belos- illars and most other larvee; its func- 
toma. c, cecum; i, ileum; —". , 
mm mid intestine: mt, Mal- 10m 18 absorptron; he colon, often 
bigbian “tubes; > ser -cabsemt, issevident im Orthopterayamad 
reservoir; s, salivary gland. 
—After Locy, from the Lepidoptera and may bear (Benacus, 
al Dytiscus, Silphide, Lepidoptera) a con- 
spicuous cecal appendage (Figs. 148, 150) of doubtful func- 
tion, though possibly a reservoir for -excretions. The colon 
contains indigestible matter and the waste products of diges- 
tion, including the excretions of the Malpighian tubes. The 
rectum (Fig. 145) is thick-walled, strongly muscular and often 
folded internally. Its office is to expel excrementitious matter, 
consisting largely of the indigestible substances chitin, cellulose 
