7° 



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. 



Fig. 31. 



Cross Section oj Ileum ^ after 

 Schiemenz, 



AUmeiilary Canal, modified, from Wolff. 



o Esophagus. J m Stomach-mouth. 



A s Honey -stomach. ,! True stomach. 



c Urinary tubes. i Small intestine or ileum. 



r ff Rectal glands. r Large intestine or rectum. 



The mouth I have already described. Following this 

 is the throat or pharynx, then the esophagus or gullet 

 (Fig. 21, o), which may expand, as in the bee, to form a 

 honey stomach (Fig. 21, h s), 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. 2\,s). Following 

 this is the intestine— separated by some authors into an 

 ileum (Fig. 21, i) and a rectum, which ends in the vent 

 or anus. Connected with the mouth are salivary glands 

 (F'g. 38), which are structurally like those in higher 

 animals, and in those larvae that form cocoons are the 

 source of silk. In the glands this is a viscid fluid, but as 



