Insecta. 7 



ment of the respiratory system, which conveys air to all 

 parts constantly. Thus the insect is enabled to exert its 

 muscles powerfully and rapidly, and in general maintain 

 the high degree of activity which is so characteristic of 

 ihe group. As might be expected, the temperature of 

 insects is high, compared with that of invertebrates in 

 general, being several degrees above that of the surround- 

 ing air. 



The Grasshopper's Food and Digestion. Eating is a large 

 factor in the life of the grasshopper. We see it on many 

 kinds of plants, gnawing leaves and stems with its short, 

 strong, laterally moving jaws. The narrow gullet extends 

 upward to about the center of the head, then turns pos- 

 teriorly and dilates into the crop, which runs lengthwise 

 in the thorax. At about the beginning of the abdomen 

 the crop narrows somewhat and becomes the stomach. 

 Alongside the crop are the branched salivary glands, whose 

 ducts run forward to empty into the mouth. At the place 

 where the crop joins the stomach it is surrounded by a set 

 of six or eight double-cone-shaped pouches extending par- 

 allel to the digestive tube itself. These bodies are the 

 ceca. They are hollow and communicate with the cavity 

 of the digestive tube by openings. The ceca secrete a 

 liquid that aids in digestion ; they increase the surface of 

 the digestive tract and probably are largely concerned in 

 the work of absorption. The stomach extends about half 

 the length of the abdomen. Its posterior limit is marked 

 by a large number of slender tubes, the urinary tubes, 

 which enter the digestive tube at the juncture of the stom- 

 ach and intestine. The last part of the intestine is some- 

 what dilated, forming the rectum, which, in turn, terminates 

 in the anal opening at the upper part of the end of the 

 abdomen. 



