MOSQUITOES. 



245 



then place the body in a drop of salt solution on a slide. Then hold 

 the anterior end of the thorax by pressure of a needle. With a needle 

 in the other hand, gently crush the chitinous connection between the 

 sixth and seventh segments of the abdomen. Then holding the thorax 

 firm, steadily and gently pull the last segments in the opposite direction. 

 If this is done properly, a delicate gelatinous white mass will slowly 

 float out in the salt solution. One should be able to secure the aliment- 

 ary canal as far up as the proventriculus, which is just anterior to the 



FIG. 77. Anatomy of mosquito, i, Cross section of proboscis of mosquito; 

 2. anatomy of mosquito longitudinal section; 3, tip of proboscis of mosquito; 

 a, labrum-epipharynx; b, hypopharynx; c, mandible; d, maxilla. 



stomach, the part in which the malarial zygotes develop. Proceeding 

 from before backward, we have the proventriculus, which is a sort of 

 muscular ring at the opening of the stomach or mid-gut. Leading 

 from the stomach we have the hind gut, which ends in the rectum. 

 Taking origin at the posterior end of the stomach and festooning the 

 hind gut are 5 longitudinal tubes the Malpighian tubules. These are 

 characterized by large granular-like cells with a prominent refractile 

 nucleus. They are regarded as the renal structures. It is in these 

 tubules that the embryo of the Filaria immitis of the dog develops. 



