86 



Insects and Disease 



breathing-pores. These are the openings into the 

 tracheal or respiratory system. 



THE ABDOMEN 



The long cylindrical abdomen is composed of 

 eight segments. These are rather strongly chiti- 

 nized above and below, but a narrow strip along 

 the side is unchitinized. In this strip are situated 

 the abdominal breathing-pores. The tip of the 

 abdomen is furnished with a pair of movable 

 organs, which in the male are variously modified 

 and serve as clasping organs at mating time. 



THE DIGESTIVE SYSTEM 



The mouth-parts of the mosquito have just been 

 described. It will be remembered that the labrum 

 is provided with a groove. Through this the blood 

 or other food is sucked up by means of a strong- 

 walled pumping organ, the pharynx, situated in 

 the head (Fig. 70). Just back of the pharynx is the 

 esophagus which leads to the beginning of the 

 stomach. Close to its posterior end the esophagus 

 gives off three food reservoirs, two above and a 

 single larger one below. In dissections these will 

 often be seen to be filled with minute bubbles. The 

 stomach reaches from the middle of the thorax to 

 beyond the middle of the abdomen. At its pos- 



