680 THE POPULAR SCIENCE MONTHLY. 



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 Beuten- 

 muller, of New York, for papers on The Utility of Dragon-Flies 

 as Destroyers of Mosquitoes and on the Destruction of the Mos- 

 quito. These, with other contributed papers, are embodied in the 

 volume. From Mrs. Aaron's essay we learn that the Culicidce*, or 

 mosquitoes, breed in stagnant water, and have been observed 

 living, in all stages of growth, in the most insignificant pud- 

 dles — 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 by- 

 ways, and garden ditches are the most fruitful places for recruit- 

 ing 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, feed- 

 ing on decaying substances in stagnant water, has not been con- 

 firmed 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 



