vie) Digestive System in Insects. 
ing air, and are thus called rat-tailed. Even the pupa of , 
the mosquito, awaiting in its liquid home the glad time 
when it shall unfold its tiny wings and pipe its war-note, 
has a similar arrangement to secure the gaseous pabulum. 
The digestive apparatus of insects is very interesting, 
and, as in our own class of animals, varies very much in 
length and complexity, as the hosts of insects vary in their 
habits. As in mammals and birds, the length, with some 
striking exceptions, varies with the food. Carnivorous or 
flesh-eating insects have a short alimentary canal, while 
in those that feed on vegetable food it is much longer. 
Fic. 21. 
A 
Cross Section of Ileum, after 
Schiemenz, 
Alimentary Canal, modified, from Wolff. 
o Esophagus. s m Stomach-mouth. 
4 s Honey-stomach, s True stomach, 
¢ Urinary tubes, # Small intestine or ileum. 
r g Rectal glands. ry Large intestine or rectum. 
The mouth I have already described. Following this 
is the throat or pharynx, then the esophagus or gullet 
(Fig. 21, 0), which may expand, as in the bee, to form a 
honey stomach (Fig. 21, 2s), may have an attached crop 
like the chicken, ‘or may run as a uniform tube, as in the 
human body, to the true stomach (Fig.21,s). Following 
this is the intestine—separated by some authors into an 
ileum (Fig. 21,2) and a rectum, which ends in the vent 
or anus. Connected with the mouth are salivary glands 
(Fig. 38), which are structurally like those in higher 
animals, and in those larve that form cocoons are the 
source of silk. In the glands this is a viscid fluid, but as 
