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Rh or pupæ, from which, by a rupture of the pupa-case, the adult insects or imagines emerge.

The geographical range of the mosquito extends from the frigid zones to the equator. Given stagnant or slow-flowing water and a summer temperature, there this family of insects will be represented by one or many species. The distribution of particular species and the abundance of mosquitoes in any given place are determined, in addition to temperature and hydrographic conditions, by complicated circumstances not yet wholly understood.

The adult insect feeds on vegetable juices; the males, with few exceptions, exclusively so. In

Fig. 24.—Various forms of mosquito eggs.

addition to a vegetable diet, the females of most species, when opportunity offers, suck the blood of mammals, birds, occasionally of fishes, reptiles, and even that of other insects and their larvæ. The male mosquito, not being a blood-sucker, takes no part in the diffusion of disease; it is the female only that is a germ carrier.

Soon after impregnation the female lays her eggs (Figs. 24, 25, 26) from time to time—singly, in groups, or in boat-shaped masses, according to species—either on the surface of still water, on which they float, or in propinquity to water. The process of hatching out depends in great measure, as indeed do all the developmental processes connected with the mosquito, on temperature, being retarded or even