312 THE MOSQUITOES 



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 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. 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 five longitudinal tubes the Malpighian tubules. These are characterized 

 by large granular-like cells with a prominent refractile nucleus. They are re- 

 garded 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 In the female mosquito, the parts withdrawn may 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 spermathecae, 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 sur- 

 face, 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 ex- 

 ceedingly highly refractile appearance. To stain for sporozoites, pick up the head 

 end, and with forceps draw the severed neck along a clean dry slide, trying at the 

 same time to smear out the adherent salivary glands. After drying, stain 

 with Wright's stain. The sporozoites are narrow falciform bodies about I2/J. in 

 length, with a central chromatin dot. 



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

 communicate with the alimentary canal. Theobald states that there is no con- 

 nection between them. 



DIFFERENTIATION OF CULICIN^E 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 probable 

 malaria transmitter or not. 



While certain characteristics of the male are used to separate the 

 ^Edinae from other subfamilies, yet it is only with the female that we 

 concern ourselves in differentiating the Culicinae from the Anophelinae. 

 Therefore, it is first necessary to distinguish the male from the female. 

 If the antennae have not been torn off, this can be decided by the highly 

 adorned plumose antennae of the male, those of the female being sparsely 



