16 



INSECTS INJURIOUS TO STAPLE CROPS. 



smaller tubes to all of its organs and tissues. Fresh air is 

 thus inhaled to all parts of the body through these tubes 

 (Fig. 8, tr). 



Fig 8. — Diagram of tracheal or breathing system of an Insect, 

 .s-ij-s^jo, the ten pairs of spiracles; A, head; i?i_3, the three seg- 

 ments of the thorax; Tr., the two main tracheal trunks; trs., 

 trachea leading from the main trunk to the spiracle; tru., tra- 

 chea connecting the two main trachea; tri., visceral trachea; 

 tro., ventral trachea; tr., the anterior termination of the tra- 

 chea; g.-g., nerve-cord with ganglia to wiiich go branches of 

 the visceral trachea; au., eyes; a, antennae; p, palpi; m, man- 

 dibles; jPi-p^, bases of the legs. (After Kolbe.) 



The blood of insects does not circulate through any 

 system of tubes as it does in the higher animals. Along 



