[Illustration: FIG. 6.--Various forms of Mosquito Eggs. (1) Egg-boat of _Culex_, seen from above; (2) the same, side view (after Sambon); (3) separate _Culex_ eggs; (4) eggs of _Panoplites_ (after Daniels); (5) eggs of _Stegomyia_; (6) the same more highly magnified (after Theobald); (7) groups of _Anopheles_ eggs as they float on the water (after Sambon); (8) egg of _Anopheles maculipennis_, showing lateral floats, seen from above, × 30 diams.; (9) the same, viewed laterally (after Nuttall).] With the exception of the fleas and ticks, no insects are so admirably adapted for the conveyance of disease from one animal to another by inoculation; and owing to their enormous numbers, and their capability of flight, their powers of mischief must be far greater than those of either of these other pests. When biting an animal, the mosquito injects into its tissues a fluid specially secreted within its body, which being of an irritating character causes a congestion of blood round the puncture, whereby the insect is secured a full and ample feed of blood. The early life of the mosquito is passed in water, on the surface of which the eggs are laid by the female flying insects. These eggs are of various forms, but are all provided with some arrangement to secure their floating on the surface of the water. In many species they are glued together by their sides so as to form rafts consisting of some hundreds of eggs, while in others, and notably in the special sorts that carry malaria, they are laid separately and float on their sides. In a few rare cases they may be laid on dry surfaces, in situations that will be flooded during the rains. This is notably the case occasionally with the form that carries yellow fever; but for practical purposes it may be considered that the eggs can only be laid on water, and in any case, when the young insects are hatched out, it must needs be into water, as at that stage of their existence they are purely aquatic organisms, and live but a short time if removed from the water. In spite of this they are air-breathers, and in the anatomy of their arrangements for obtaining air, present a curious resemblance to the type of submarine boat that gets its air by means of a small tube reaching just above the surface of the water. The young mosquitoes, or larvæ, are small, wormlike animals, which may often be seen wriggling about vigorously in water, and are especially common, in warm weather, in water standing in small stagnant pools, broken crockery, old tins, and so forth.