Page:Popular Science Monthly Volume 37.djvu/698

680 probable efficiency for reducing the numbers of the hosts of these enemies of mankind. The prizes were awarded by a committee consisting of Drs. H. C. McCook and J. S. Newberry—the first prize to Mrs. Eugene Aaron, of Philadelphia, for an essay on The Dipterous Enemies of Man; and the second prize equally divided between Messrs. Archibald C. Weeks and William Beutenmuller, of New York, for papers on The Utility of Dragon-Flies as Destroyers of Mosquitoes and on the Destruction of the Mosquito. These, with other contributed papers, are embodied in the volume. From Mrs. Aaron's essay we learn that the Culicidæ, or mosquitoes, breed in stagnant water, and have been observed living, in all stages of growth, in the most insignificant puddles—as "in a puddle of water, eight inches square and one inch deep, made by the rain in an iron pulley in a foundry-yard. They are also to be observed teeming to overcrowding in the hoof-holes in boggy cow-pastures. But the shallows occasionally overflowed and replenished by rivulets in swamps, the stagnant pools formed by ditches without outlets, and the vastly more numerous murky pools made by the joining of tufts of grass in marshes, are the usual breeding-places in the rural districts. In village and urban localities rain-tanks, undrained gutters, badly paved, damp byways, and garden ditches are the most fruitful places for recruiting their numbers. These surroundings are selected by the female with a view to the fact that from three to four weeks will be required to perfect the changes from the egg to the imago; and they must be situated so as to receive sufficient water from rain or outside overflow to replenish the evaporation or soaking into the ground. In this selection the female shows the usual instinct which is so noticeable in insect economies." When hatched, they hug the sides of pools and shallow margins, and, spending most of the time at the surface with the orifice of the air-tube just in contact with the air, are not usually found at great depths. They are easily frightened by any stir or motion from above, but pay little attention to any dangers that may menace them from the water. Very little is known of their feeding habits; but the statement that they are scavengers, feeding on decaying substances in stagnant water, has not been confirmed or disproved. They have been observed to feed on minute animals, and to destroy young trout. They go through several transformations, and reach a curious shape in the pupa, which—the head, thorax, legs, and wings, all being folded in one mass, and the abdominal segments being left free for the purpose of navigation—has a top-heavy and clumsy appearance, although it is quite as active as the larva. After the insect has matured and has begun its flight, the principal objects in its remaining brief existence "are the search for the desired mate and the duties of