THE INSECT: ITS INTERNAL STRUCTURE 



17 



suggests the idea that absorption in those cases has not been completed 

 when the food leaves the stomach but continues in the hind-intestine. 

 Opening into the mouth is a tube leading to the sahvary glands, which 

 generally lie in the front of the thorax and appear to have a similar func- 

 tion to those in man. In some cases other glands for different purposes 

 are also present in the head or front of the thorax and open into the 

 mouth. 



Fig. 24. — Internal anatomy of the Honey Bee showing alimentary canal, tracheal and 

 nervous systems, ce, compound eye; hi, hind intestine; hs, honey sac; It, lateral trachea 

 (enlarged); mt, malpighian tubes; nj, rectal glands; s, stomach; sp, spiracles. {Modified 

 from Leuckart's Wandtafeln.) 



Some of the poisons used in control measures are swallowed by the 

 insect, passing to the stomach and there are dissolved by the digestive 

 juices. Thus dissolved, they set up inflammation of the stomach walls 

 and finally cause death. Poisons acting in this way are called "stomach 

 poisons." 



Breathing Organs. — Respiration in insects is accomplished by a 

 method which is nearly unique. The oxygen needed, instead of being 



