HOW INSECTS BREATHE 175 



The furrows are in fact, a sort of long soft hinge by means of 

 which the hard lower wall of the body can be moved away from 

 or towards the hard upper wall, and the size of the body thus 

 made larger or smaller. This making the body larger or smaller 

 is the breathing motion. 



Does the air which the locust breathes pass in thru the 

 mouth ? If not, where does the air pass in and out of the body ? 

 Unfortunately the children will not be able to prove that the 

 locust does not breathe thru its mouth — it does not: nor that the 

 air does pass in and out of the body thru a series of tiny holes on 

 each side of the body — which it does. It may be readily seen, 

 however, that on each side of each body ring or segment there is 

 just above the long lateral furrow, and near the front edge of the 

 segment, a small spot. This is a minute opening in the body 

 wall, and is a breathing pore or spiracle. Thru these holes, each 

 time the bodj' expands, the air passes into the body, and out of 

 them the air comes each time the body contracts. On the inside 

 of the body leading from these breathing openings are small tubes 

 which carry the air into two air trunks, which run longitudinally 

 along each side of the body and extend in most insects for almost 

 the entire length of the body. From these main trunks arise 

 many subordinate trunks, these in turn subdivide into numerous 

 finer branches which branch again and again, so that every part 

 of the body is reached by these air tubes, and all the organs and 

 tissues, of the body thus directly supplied with oxygen. 



These air tubes or trachea, can be Ireadily shown to the class. 

 The teacher should prepare a simple dissection of some large 

 insect — a caterpillar makes an especially good object — revealing 

 the main longitudinal trunks and some of the branches. Make 

 the dissection as follows: Glue, witli water proof glue, a piece of 

 sheet cork to the bottom of a small, shallow tin dish or earthen- 

 ware saucer. Pin the caterpillar, which has been killed by 

 chloroform, outstretched with back uppermost to the cork. With 



