The warfare declared against mosquitoes in America, suggested by Dr. Howard, has attracted widespread attention to these insects, which have rendered many localities absolutely uninhabitable. A Florida physician informed me that in a certain locality horses had been killed by these insatiate bloodsuckers, which are now known to be the carriers of the germs of yellow fever. Over almost every pond or pool in summer they may be seen in countless numbers, filling the air with their disagreeable music. [Illustration: FIG. 223.--Proboscis of a mosquito.] The proboscis, or sucking weapon, of the mosquito (Fig. 223) is an innocent-appearing object when closed; but when the sheath is open it displays a series of scimeter and sawtooth daggers (Fig. 224), which fully explains the torture of the mosquito bite or that of the gnat which crawls up one's sleeve (Fig. 225). In all these extraordinary weapons we find the same organs, the labium, labrum, and others, but with greater or less development, according to the nature of the insect. [Illustration: FIG. 224.--Proboscis of a mosquito open.] [Illustration: FIG. 225.--Biting organs of a gnat.] It is the female mosquito which occasions all the trouble and renders mankind miserable in some of the otherwise most delightful resorts. On the Florida Keys I always had a mosquito bar overhead, not merely over the bed but suspended from the ceiling in midday. Even then these pests would force their way through the meshes. [Illustration: FIG. 226.--Development of the mosquito.] The development of the mosquito is interesting (Fig. 226). The eggs are deposited as a boat-shaped mass on the surface of the water, where they drift about for several days. The larvæ appear as wigglers floating in the water, tail upward, and breathing through a tube at the tip of the abdomen which is projected above the water for the purpose. After a while the head grows larger, and several changes ensue. Then the pupa finally appears. This rises to the surface, and out bursts a full-fledged mosquito which, like a man in a canoe, balances itself while its wings dry. A few hours before it was entirely dependent upon the water and swimming in it, but now it appears to be fearful of overturning the frail craft and falling in where it would surely drown. If all goes well, it soon tries its wings and goes buzzing away. The devastation caused by the armed and bewhiskered mosquito is not generally known. Doubtless thousands have lost their lives from this unsuspected cause. [Illustration: FIG. 227.--The gnat (_Culex_) and its development from the egg: _A_, egg; _B_, larva; _C_, pupa; _D_, adult.] The common gnat (Fig. 227) has habits similar to those of the mosquito. They are often seen floating in the air in great swarms or bands, rising and forming as though in some mystic dance. [Illustration: FIG. 228.--The flea and its development.]