DIPT ERA 



299 



The small group of mosquitoes of the subfamily, Corethrinoe, have 

 short probosces unfitted for sucking blood. The larvae of these forms 

 are predacious and live on infusoria, small crustaceans and small larvae of 

 other mosquitoes. All of our common mosquitoes belong to the sub- 

 family, Culicince, the more important ones to the genera, Culex, Anopheles 

 and Aides. 



Culex. — To this genus belong our common house mosquitoes that 

 have unspotted wings and short palpi in the females. 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 except one species which conveys the organism causing 

 elephantiasis. 



Aides. — This is a very large genus of world-wide distribution. The 

 species vary greatly in habits; but with most of them the larvae develop 

 from over-wintering eggs in early spring pools. Some species, however, 

 breed in water-barrels, and other artificial containers; one of these is the 

 carrier of yellow fever. 



The yellow-fever mosquito, Aides cegypti, is distributed throughout 

 all tropical regions of the world and is often carried by commerce into 

 temperate regions. But as it is destroyed by frost it can not become 

 established when frosts occur. Hence outbreaks of yellow fever in the 

 North are checked naturally as winter approaches, and with our present 

 knowledge of the method of control of this disease it is not probable that 

 it will be permitted to become epidemic again in the "United States. 



The yellow-fever mosquito breeds in cisterns, water-barrels, flower- 

 vases, and in the various water receptacles about houses. The life-cycle 

 under favorable conditions is completed in from twelve to fifteen days. 

 This is essentially a domesticated species. It is rarely found far from the 

 habitations of man. 



Anopheles. — To this genus belong those mosquitoes that have been 

 found to be the carriers of malaria. At least four species of Anopheles 

 in the United States, are known to be carriers of this disease. In this 

 genus the palpi of both sexes are nearly or quite as long as the proboscis 

 and the wings are frequently spotted. When at rest on a vertical wall 

 the body is usually held at an angle with the vertical. Some species often 

 enter houses. They hibernate in the adult state and can be found during 

 the winter in cellars. 



The larva when at rest floats in a 

 horizontal position beneath the sur- 

 face film (Fig. 5r6). There is no res- 

 piratory tube but instead a flattened 

 area on the eighth abdominal segment 

 into which the two spiracles open. FlG _ Sl6 __ Normal posit!on of the larviE of Cuhx 



Other mOSquitO-bome diseases Of an .d Anopheles when at rest. Culex, left, Anopheles, 

 T \ . , • , 1 middle; Culex pupa, right hand figure. 



man. — In tropical countries there are, 



in addition to malaria and yellow fever, two other diseases of man that 

 have been found to be transmitted by mosquitoes; these are dengue and 

 filariasis. The latter disease is accompanied by extraordinary deformities 

 and enlargements of different parts of the human body known as ele- 

 phantiasis. Filariasis is due to the presence in the blood, the lymphatics, 

 and certain tissues of the body, of nematode (round) worms of the family, 

 Filariidae. These worms pass a part of their life-cycle in the bodies of 

 certain mosquitoes. 



