DIPTERA 807 



of mosquitoes; they are free-swimming and are foimd most abun- 

 dantly beyond the line of shore vegetation. The pupai are also trans- 

 parent at first but become darker colored just before transforming. 

 The females of Corethra phmiicdrnis . as observed by Professor Need- 

 ham, deposit their eggs on the surface of the water, laying them down 

 flatwise, in a spiral held together by scanty gelatine. 



A monograph of this subfamily was published by Johannsen ('03). 



Subfamily CULICIN.^ 



To this subfamily belong by far the greater number of mosquitoes. 

 With these the proboscis is longer than the head and thorax taken 

 together; this character is sufficient to distinguish them from the 

 Corethrinae. 



The Culicina^ have received much attention in recent }'ears. Since 

 the discovery that certain species are carriers of diseases of man many 

 investigators have studied mosquitoes, and thousands of papers have 

 been published regarding them. Fortunately the more important 

 results of these investigations have been summarized by several 

 writers and published in easily available books. The most important 

 contribution to this subject is the monograph by Howard, Dyar, and 

 Knab (' 1 2-' 1 7) . This is a large work in four volumes. A more avail- 

 able and more recent monograph is that of Dyar published in 1922. 



It has been demonstrated that malaria, yellow fever, filariasis, and 

 dengue are each caused by a parasitic organism, which has a complex 

 life-cycle, part of which is passed in man and part in 

 certain mosquitoes; and that it is only by being 

 bitten by an infected mosquito that one contracts 

 any of these diseases. There are also diseases of 

 other mammals and of birds that are transmitted 

 in a similar way. 



In each case the parasitic organism is restricted 

 in host relations, infecting in turn only certain 

 species of Vertebrates and certain species of mosqui- 

 toes. 



Representatives of eleven genera of the Culicinae 

 have been found in the United States. Some of these 



occur only in the extreme South and others are either 

 rare or rarely attack man. The species that are our 

 most serious pests are included in the genera Culex, 

 Anopheles, and Aedes. 



Culex. — To this genus belong our common house 

 mosquitoes that have unspotted wings and short 

 palpi in the females and which when at rest on a 

 vertical wall hold the body parallel with the wall or 

 with the tip of the abdomen inclined toward it (Fig. 

 1024) . These are very annoying pests ; but although 

 many of the species of this genus transmit blood 

 diseases of birds and animals they do not play an important role in 

 human diseases. 



Fig. 1024. — Nor- 

 mal position 

 of Cnlex and 

 Anopheles on 

 a wall; Culex 

 above, Ano- 

 pheles below, 

 (From Ri]ey 

 and Johann- 

 sen.) 



