1904 



ENTOMOLOGICAL SOCIETY. 



99 



The nervous system lies below the alimentary canal, and close to the 

 lower body wall. It is composed of a series of ganglia connected by two 

 long, slender cords. The ganglia in the head is the largest, and supplies 

 nerves to the eyes, feelers, and mouth. In general, each segment of the body 

 has a ganglion which sends off nerves in all directions, to supply the segment. 



Fk;. is. Month parts of 

 a House-fly. 



Fig. 20. Under surface of Head and Thorax of a Si^uaeh 

 bug ; a the odour glands ; b the sucking beak ; c the 

 antenna'. ( Original ) . 



The respiratory system is clearly shown in Fig. 22. The breathing- 

 pores, or spiracles, are valve-like openings lying along each side, and open al- 

 most directly into a tube which runs lengthwise of the body. From these 



Fig. 21. Caterpillar showing i>ro-legs as well as feet. 



two main tubes branches run in all directions through the body to the main 

 organs. In many insects there are bulb-like expansions which act as air- 

 reservoirs. By means of the system of tubes, or tracheae, air is carried to all 

 portions of the body, and the blood is rapidly purified by exchanging carbon- 



