10 MOSQUITOES or NORTH AMEEICA 



We have referred above to fatmal regions, or large areas occupied by a com- 

 plex of species which, in general, do not extend beyond these areas. Snch areas 

 exist for all classes of plants and animals and, in a broad way, coincide for all. 

 They have been mapped for North America in some detail by Dr. C. Hart 

 Merriam (TJ. S. Dept. Agr., Div. Biol. Snrv., Bull. 10, 1898). These areas 

 differ somewhat for different classes of animals. In many they are conditioned 

 by the distribution of food-plants or other hosts, but, in mosquitoes, these re- 

 strictions operate to only a slight degree, and, in consequence, the faunal areas 

 of mosquitoes are large. They are determined by climate, or rather by the effect 

 of climate upon the breeding-places. As we show elsewhere in this work, there 

 are classes of species adapted to breed in temporary puddles, in permanent 

 water, and in water held by living or dead plants. The former are of two kinds, 

 those occurring in pools the temporary nature of which is determined by a cold 

 climate, where the melting snows form pools in early spring, and those oc- 

 curring in pools formed by infrequent rains in an arid region. The species 

 inhabiting permanent water are especially adapted to a moist climate where 

 frequent rains maintain suitable collections of water. The last class are domi- 

 nant in the tropics, where many species of plants retain water in leaf -axils or 

 flower-bracts. A few species are associates of man, their larvae inhabiting water 

 in artificial receptacles, and these are largely independent of faunal regions, 

 being limited only by extremes of cold and the absence of man. 



The area covered in this work does not correspond to any one or more entire 

 faunal regions, its boxmdaries being arbitrary. The species of the arctic region 

 are treated in small part only, in so far as we find them in Canada and the 

 northern parts of the United States. The faunal regions comprising the United 

 States east and west of the Eocky Mountains are included in full, as is also that 

 of the semi-arid west, although our collections from the south-western United 

 States and the Mexican plateau are very scanty and, consequently, that part of 

 this area is imperfectly treated. The great tropical faunal region is touched by 

 our inclusion of Central America and of Trinidad, while the insular faunas of 

 flie Greater and Ijesser Antilles, which form two distinct regions, are covered 

 entirely, although necessarily incompletely. 



