Page:Popular Science Monthly Volume 37.djvu/699

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reproduction. To suppose that the tormenting of man occupies any considerable time in the mosquito economy is certainly a mistake. It is only the female which can thus make our lives miserable" They are local in their range, and the supposition that they can be carried long distances by the wind is declared a mistake. House-flies are omnipresent with us, while mosquitoes appear only in spots. According to Packard, "fresh horse-manure, with plenty of heat and moisture, furnishes the best food for the young maggot. From a hundred to a hundred and fifty eggs are deposited in irregular, loose sacs, usually within eighteen hours, and hatching in twenty-four hours or less. The maggots molt twice; the three stages of larval development being of the following periods: first stage, one day; second stage, from twenty-four to thirty-six hours; third stage, three or four days. To this maximum period of seven days is to be added the same length of time for the pupal life; thus it will be seen that fifteen or sixteen days are required for the entire development from egg to imago."

The expediency of trying to exterminate them is more than doubtful, for, according to the same author, "it should be remembered that flies have an infancy as maggots, and the loathsome life they lead as scavengers cleanses and purifies the August air, and lowers the death-rate of our cities and towns. Thus the young of the house-fly, the flesh-fly, and the blow-fly, with their thousand allies, are doing something toward purifying the pestilential air and averting the summer brood of cholera, diphtheria, and typhoid fevers which descend like harpies upon the towns and cities. It is a useful species, to which man owes more than he can readily estimate, and with which he can dispense only when the health of our cities and towns is looked after with greater vigilance and intelligence than is perhaps likely to be the case for several centuries to come."

Mosquitoes, therefore, are entitled to exclusive attention in the exterminating effort.

Mrs. Aaron has a poor opinion of the efficiency of the dragonflies, or Odonats, as mosquito-destroyers. They become rarer about the time that the mosquitoes are most numerous. In the matter of flight they are very local, and it seems impossible to conceive that they could ever be brought to frequent deep woods or city streets where mosquitoes abound. The author's observations of their feeding habits lead her to believe that they prefer robust, meaty insects, and that studies of their appetites in confinement are misleading. The habit of migration among them will also militate against their efficiency as mosquito-destroyers.

Other writers find that they are capable, in natural conditions, of working great havoc among mosquitoes, but doubt the utility of efforts to improve on nature in the matter. Captain C. B. N.