8 MOSQUITOES OF NOKTH AMERICA 



is made in parts of the table. In Culiseta, the presence or absence of a row of 

 spines on the segment preceding the last gives a good prime character. After- 

 wards the modifications of the unci are used. In Psorophora, the dilation of 

 the clasp-filament and the modifications of the appendages of the harpagones 

 are the priacipal characters. In AedeSj the harpagones are undeveloped in the 

 lowest forms; the other characters used are like those already mentioned. In 

 the succeeding genera, the characters for use become more and more restricted, 

 until in Megarhinus the species only separate into groups. In Anopheles, the 

 harpagones and harpes are both absent, and recourse is had to certain spines 

 and lobes, which are without fundamental importance, but serve for the most 

 part for a specific separation. 



The larvse, as elsewhere stated, separate into the tribes Sabethini and Culicini 

 on the absence or presence of the ventral brush on the last segment. The ventral 

 brush of the Culicini consists of a series of branched hairs inserted along the 

 mid-ventral line, each hair or tuft upon a transverse chitinous strip. These 

 chitinous strips form the so-called " barred area " ; in a few cases this is sup- 

 planted by a chitinous plate with a longitudinal series of perforations in which 

 the members of the brush are inserted. The ventral brush is rudimentary in 

 the first-stage larvae and becomes more complete at each successive stage. In 

 the Sabethini the ventral brush is absent in all stages and is represented by a 

 single opposed pair of hairs or hair-tufts. In addition to this character, a num- 

 ber of others, structural and biological, differentiate the two tribes. These have 

 been set forth in their respective places in the discussion of the tribes. 



In the Sabethini, the genera separate well, except Wyeomyia and Limatus, 

 which are in fact not truly separate genera. There is no lateral patch of scales or 

 comb on the eighth abdominal segment in Joblotia. The predaceous Sdbethinus 

 and Lesticocampa have heavily armed maxillae and separate on this character 

 from Wyeomyia and Limatus, which feed on organic matter and microorgan- 

 isms. In most of the sabethine genera we possess too few larvae to form extensive 

 tables. In Wyeomyia, however, we have a number. They separate on the struc- 

 ture of the air tube, the lateral comb and other structures requiring no especial 

 explanation. 



In the Culicini, the genera separate on the absence of the air-tube in Anoph- 

 eles; afterward by the presence or absence of pecten on the air-tube, the structure 

 of the mouth-brushes, the shape of the head, mandibles, and the completeness or 

 incompleteness of the chitinous ring on the anal segment. The specific char- 

 acters of the larvae will be easily understood from the wording of our tables, and 

 require no especial explanation. 



