CULICINE AND ANOPHELINE MOSQUITOES 371 



be able to secure the alimentary canal as far up as the proventriculus, which is just 

 anterior to the 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 and marks the separation of the stomach 

 from the cesophagus. Opening into the lower part of the oesophagus are the 

 cesophageal diverticula or crops, which are food reservoirs. Occasionally in a 

 dissection we pull out these structures which are three in number. 



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



This has a posterior dilatation or rectal pouch which usually has three or four 

 rather marked anal papillae. 



Taking origin at the posterior end of the stomach and festooning the hind-gut 

 are five 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. In the female mosquito, the parts withdrawn may seem to be 

 largely made up of the white oval ovaries. These are connected with the sperma- 

 thecae, in which the spermatozoa are stored after fecundation by the male. In the 

 male the testicles are quite distinct. Next to the examination of the stomach for 

 zygotes, which appear as wart-like excrescences on its outer surface, the most 

 important structures are the salivary glands, where the malarial sporozoites are found. 

 The easiest way to dissect out the salivary glands is to press down firmly, but gently, 

 on the anterior part of the thorax, and then with the shaft of a second needle, 

 pressing on the head to gently draw the head away from the thorax, so that by this 

 expression and traction movement you extract them with the head segment. They 

 are very minute and are to be told by their exceedingly highly refractile appearance. 

 To examine for sporozoites cover the glands protruding from the neck with a cover- 

 glass and search with a one-sixth objective for narrow, curved bodies in the sub- 

 stance of the glands. If present try to smear out the glands between the cover-glass 

 and slide by pushing the cover-glass along, then withdrawing the cover-glass, dry 

 quickly and stain the smear on slide or cover-glass with Wright's stain. 



The sporozoites are narrow falciform bodies about 12/1 in length, with a central 

 chromatin dot. 



A matter about which there is dispute is as to whether the salivary glands com- 

 municate with the alimentary canal. Theobald states that there is no connection 

 between them. 



DIFFERENTIATION OF CULICINE AND ANOPHELIN^E 



It is impossible even for an entomologist to differentiate mosquitoes 

 without recourse to elaborate keys and tables. It is a comparatively 

 easy matter, however, to decide as to whether the mosquito is a prob- 

 able malaria transmitter or not. 



While certain characteristics of the male are used to separate the .Edina; from other 

 subfamilies, yet it is only with the female that we concern ourselves in differentiating 

 the Culicinaj from the Anophelinae. Therefore, it is first necessary to distinguish 



