CULEX, GENERAL ACCOUNT 219 



separation rests essentially upon the modification of the larvae for the predaceous 

 habit, the adults being very feebly differentiated from the Culex type. In 

 Carrollia, the differentiation has gone farther, both adults and larva? having 

 acquired a distinctive habitus. On the other hand, the two forms treated here 

 under subgenera of Culex (C. melanurus, C. dyari) should more properly be 

 excluded and treated as distinct genera. The male genitalia show a much more 

 primitive type, altogether lacking the appendages of the side pieces and the 

 complex modifications of the basal structures. The adults, however, otherwise 

 present no significant characters to separate them from Culex, and the larvae 

 also follow the Culex type, so that we feel constrained, against our convictions, 

 to include them with Culex. 



The larvae generally inhabit water of a permanent character as opposed to 

 pools of rain-water or snow-water that dry in a few days. The habits of the 

 different species vary greatly. Culex pipiens and C. quinquefasciatus are fond 

 of foul water and have become semi-domesticated, frequenting the vicinity of 

 man. Man supplies to these species many excellent breeding-places sufficiently 

 foul, and furnishes in his own person an abundant source of food for the adults. 

 No other Culex will frequent as foul water as these species, in fact the others 

 generally prefer comparatively clear water, although there are several other 

 species besides Culex pipiens that inhabit rain-water barrels and other artificial 

 receptacles as well as drainage-water and open pools in our towns. 



The water in tree-holes and between the leaves of bromeliads furnishes suit- 

 able breeding-places to some species, especially to a number of tropical forms. 

 Fewer species are confined to such situations than members of other genera ; the 

 ground-pools and edges of lakes, swamps, and streams are inhabited by them 

 where there is a sufficient cover of vegetation. Some species are addicted to the 

 holes formed by crabs in mud along the tropical sea-coast. 



The eggs are laid in boat-shaped masses, containing 100 or more eggs. These 

 float on the water or remain attached to the edge of the receptacle by capillary 

 action ; the larvae hatch within a few days. Development is fairly rapid. The 

 generations succeed each other continuously as long as the conditions are suit- 

 able ; when there is a cold season the last adults hibernate and in the fall enter 

 holes, caves, or in the presence of man, sheds or cellars. Many specimens perish 

 during the hibernation period, so that the species are least numerous in in- 

 dividuals immediately after winter, and increase in numbers until unfavorable 

 weather again checks their activity. The adults are crepuscular or nocturnal in 

 habit, many being addicted to a diet in part at least of mammalian or avian 

 blood. The males swarm in the evening and morning about prominent objects, 

 preceding the union of the sexes. The length of life of the males, while not 

 positively determined, is probably of short duration. 



Some species of exceptional habits are included in the genus. A number of the 

 species are inhabitants of water between the leaves of bromeliaceous plants, and 

 these have modified larvae with greatly elongated air-tubes. Their eggs are laid 

 inclosed in a gelatinous capsule, each egg surrounded by its own layer of gum, 

 the whole resembling a mass of frog's eggs. Again, Culex melanurus lays its 

 whitish eggs singly on the water-surface, and passes the winter as fully-grown 

 larva. In this case the adults remaining in the fall perish, the species being con- 

 tinued over the winter only by its matured larva. Further, Culex dyari passes 

 the winter in the egg state and has but a single brood in the year, exactly like 

 an Aedes. The eggs are probably laid singly. The two last mentioned species 

 are distinctly more primitive in character than the other species as shown espe- 

 cially by the male genitalia. 



The genus Isostomyia is based upon a species of Culex, but nevertheless can 

 not be quoted in the synonymy of this genus. The species which furnished 

 Coquillett the basis for his genus was wrongly supposed by him to be the Aedes 



