FORM AND FUNCTION 



273 



together, in pairs, three pairs in the thorax and five 

 pairs in the abdomen. They are joined to each other 

 and to the ones of the corresponding side by a cord of 

 nerve tissue known as a commissure. This forms a 

 double chain from the back part of the body up to the 

 head, where a nerve band is formed around the esopha- 

 gus; on the top of the esophagus are to be found the 

 two largest ganglia in the body of the insect. From 

 these ganglia, nerves proceed to various parts of the 

 head. From these there go out brunches of nerves fo 

 the eyes, to the antennae, to the maxilla- and mandibles, 

 and to other parts of the face. 



Make a drawing showing the nervous system and 

 the position of the ganglia with reference to their 

 respective segments on the -body. 



FIG. 210. Respiratory system. Sp, spiracles, showing trachea) permeating all parts of the body ; 

 S, air-sacs, which aid flight. Enlarged three times. 



RESPIRATORY SYSTEM. 



This insect, instead of having one portion of the 

 body set apart for the purification of the blood, similar 

 to animals possessing lungs, may be said to have lungs 

 all over its system; that is, there are trachea 1 branched 

 and branched until thev cover everv part of the system 



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