The discovery that certain mosquitoes carry the organisms of malaria and other diseases has started a crusade against these pests. We now feel that mosquitoes must be controlled, both as a sanitary measure and as a relief against the insects themselves.
The chief mode of attack is to destroy their breeding-places. They breed only in standing water. Draining the breeding-places, or filling them up and emptying all receptacles in which water stands, is the first thing to be considered. The big gray mosquitoes that breed in tide marshes are specially pestiferous. They propagate in the brackish pools. These pools should be filled or drained, or else the tide dyked out so that the pools may dry.
The second thing to consider, if the above cannot be carried out, is to cover the breeding-pools with oil so that mosquito larvae may be deprived of air (they rise to the surface to breathe).
In fountain tanks, lily ponds, and other water areas that are to be retained, the mosquitoes may be kept down by stocking with fish that eat the larvae or wrigglers.
Kerosene for mosquitoes (Needham).
An ounce of kerosene to every 15 square feet of surface is about the right proportion, according to Howard. The film of oil will be retained for about two weeks. The grade of kerosene known as " light fuel oil " is best.
Any kerosene will kill aquatic plants, if sprayed on them. It should be poured on surface of water in cultivated ponds and spread with a broom or mop. It should be applied oftener than once in two weeks in such cases, and in much less quantity. One-fourth as much twice as often will probably be equally effective.
It is best not to use kerosene at all on ornamental ponds; it is unsightly ; it smells badly; it kills all larvae that require air derived from the surface, including those of many of the higher diptera which as adults are useful flower pollinators; it endangers the plants even when most carefully applied, to say nothing of smearing them.
1. Goldfish eat eggs by preference, also the larvae. They thrive in any warm pool, or even in cisterns with scant light; eat prepared foods, so can be readily supplied with supplemental food if necessary. They are easily obtained in the market, and are ornamental. Must be taken indoors for winter.
2. Top minnows are natural enemies of mosquitoes in native water. They are hardy and long-lived; but they are not on the market, and have to be sought with a seine. Not especially ornamental.
3. Sunfish are fond of mosquito larvae. They do well only in midst of aquatic growth; require much food, and insect food is preferred. Ornamental.
4. Sticklebacks are most voracious mosquito enemies, and are also worthy of cultivation for their remarkable nest-building habits. Rather particular as to conditions, but in proper pools they are hardy.
All these fishes require room in which pasturage may grow. A pair of the smallest of them would probably find scant natural food in a square rod of water area.
Some mosquitoes hibernate in cellars, and from them the breeding starts in spring. Cellars may be fumigated with powdered Datura Stramonium (Jimpson weed), or with culicide (culex is the generic name of the greater number of mosquitoes). In either case, according to J. B. Smith, the cellar to be fumigated should be as tightly closed as possible, to hold the fumes and make them most effective. The powdered stramonium is used at the rate of eight ounces for each 1000 cubic feet of space, mixed with one-third its weight of saltpeter to facilitate combustion. Spread the mass out on a tin plate or stone flag and light at several points to hasten the burning. The vapor is not dangerous to human life, so even if some escapes into the rooms above, no harm will be done. If the cellar is leaky, use two or three times as much as advised, and in all cases keep it as tightly closed as possible for two hours at least.