National Geographic : 1944 Feb
lThe National Geographic Magazine U. S . Public Health Service With a Sieve of Mesh-silk Bolting Cloth, He Strains Mosquito Larvae from the Water These United States Public Health Service entomologists collect larvae and the tiny organisms on which they feed, in a favorite mosquito breeding place. The man at right holds a testing apparatus which tells whether the pond water is acid or alkaline. From their detailed studies, more effective mosquito-control measures may be devised. the wards. The mosquitoes bred in large num bers in the water in the saucers under the pots. So abundant were the winged carriers that few persons who entered the hospital escaped contracting the disease. The adult yellow fever mosquito does not survive cold weather, so that, unlike Culex, it does not hibernate. The eggs, however, will stand considerable cold, remaining fertile through the winter. When mosquitoes carry a disease, the germ goes through part of its life cycle in the mos quito. It is really a disease of the mosquito, too, and a man cannot contract the disease unless he be bitten by an infected mosquito (Plate IV). The Anopheles, or malaria mosquitoes, mostly prefer to breed in open water contain ing water plants and algae, such as shallow, weedy ponds, roadside ditches, swamps, and the margins of slow-running streams. Some kinds breed in swift streams, in the water in rotted-out holes in trees, and in water-holding plants, pots, cans, barrels, and other artificial containers. The eggs are laid singly upon the water, and the wigglers, unlike those of most other mos quitoes, rest with their bodies parallel to the surface, where they do most of their feeding (Plate II). The adults, at least in the north, pass the winter in hollow logs, under bark, or in houses, cellars, or barns, as do those of the Culex mosquito. Most of the mosquitoes which annoy us out of doors, such as the salt-marsh mosquitoes of New Jersey and other parts of our coast, those of the northern plains area, and the woodland kinds, belong to the genera Aedes and Pso rophora. These generally breed in rain-water puddles, pools formed by melting snow in the spring, or in water left by high spring tides in the salt marshes (Plate VII).