SB 818 No. 13, SECOND SERIES. C578 se phi | ENT uted States Department of Agriculture, DIVISION OF ENTOMOLOGY. MOSQUITOES AND FLEAS. I.—MOSQUITOES. We are accustomed to think of but a single species of mosquito, and of this as occurring in most parts of the country, but as a matter of fact Osten Sacken’s Catalogue of the Diptera records twenty-one species from North America, and Mr. F. W. Urich states that he has observed at least ten species in Trinidad. Twenty species are contained in the collection of the U. S. National Museum. The following statement concerning the life history of these insects is based upon a series of observations made in this Division upon the development of two summer generations of Culex pungens, one of our commonest and most widespread species. The writer has seen speci- mens of this insect from New Hampshire, Massachusetts, New York, Maryland, District of Columbia, Illinois, Minnesota, Kentucky, Nebraska, ‘Louisiana, Georgia, and the Island of Jamaica, West Indies. No doubt it is also abundant in New Jersey. Egg-laying takes place at night. The eggs are deposited in boat- shaped masses on ‘the surface of the water, the number varying from 200 to 400 in each mass. The eggs may hatch in sixteen hours. The larvee live beneath the surface of the water, coming to the top at fre- quent intervals to breathe. The larval state may be completed in seven days; the pupal state may last only twenty-four hours. Anentire gen- eration in summer time, then, may be completed in ten days. This length of time, however, may be almost indefinitely enlarged if the weather be cool. There are, therefore, many generations in the course of a season and the insect may breed successfully in a more or less transient surface pool of water. Mosquitoes hibernate in the adult condition in cellars and outhouses and under all sorts of shelter. The degree of cold makes no difference in successful hibernation ; mosquitoes are abundant in the arctic regions. REMEDIES. ‘Of remedies against mosquitoes in houses the best is a thorough screening of windows and the placing of nets about beds. If the insects are troublesome in sitting or sleeping rooms during the evening, the burning of pyrethrum will so stupefy them as to make their presence unobjectionable. Pyrethrum for this purpose should be prepared by moistening the powder sufficiently to allow of its being roughly molded by hand into little cones about the size and shape of a large chocolate drop. These cones are then placed in a pan and thoroughly dried in an oven. When fired at the apex, such a cone will smoulder slowly, and send up a thin column of pungent smoke, not hurtful to man, but stupefying to mosquitoes. In actual experience two or three such cones burned during the course of an evening have given much relief from mosquitoes in sitting rooms. It does not kill the insects, however, and is at best but a palliative. 2 The mosquitoes found on the ceilings of bedrooms in the evening may be quickly and easily killed by means of a small shallow tin cup (such as the lid of a blacking box) nailed to the top of a stick and wet inside with kerosene. This cup is placed over the quiescent mosquito, which immediately drops or flies against the oily surface and is killed. But altogether the most satisfactory means of fighting mosquitoes are those which are directed to the destruction of the larvie or the abolition of breeding places. These measures are not everywhere feasible, but in many places there is absolutely no necessity for the endurance of the mosquito plague. The principal remedies of this class are three: The draining of ponds and marshes, the introduction of fish into fishless pools, and the use of kerosene on the surface of the water. The draining of breeding pools needs no discussion. Obviously the drying up of such places will prevent mosquitoes from breeding therein, and the conditions of a successful application of this measure will, it is equally obvious, vary with each case. The introduction of fish into fishless ponds is feasible and advisable in many cases where the use of kerosene on the surface of the water would be thought undesirable. In tanks supplying drinking water, for example, fish would destroy the mosquito larve as fast ag hatched. A case is recorded in Insect Life (Vol. IV, p. 223) where carp were employed in this way with perfect success by an English gentleman living in the Riviera. At San Diego, Tex., the people use for this pur- pose a little fish, called there a perch, the species of which the writer has not been able to ascertain. Probably the common voracious little stickle-back would answer admirably as a mosquito destroyer. Probably the best, and certainly the easiest, of wholesale remedies against mosquitoes is the application of kerosene to the surface of breeding pools. The suggestion that kerosene could be used as a remedy for mosquitoes is not new and has been made more than once. Exact experiments out of doors and on a large scale were made in 1892 by the writer. These and subsequent experiments show that approximately 1 ounce of kerosene to each 15 square feet of water surface on small pools will effectually destroy all the larve and pup in that pool, with the additional advantage that the adult females,not deterred from attempt- ing to oviposit, are killed when they alight on the kerosene-covered water. Ordinarily the application need not be renewed for a month, though varying circumstances may require more frequent applications in certain cases. Since 1892 several demonstrations, on large and small scales, have been made of the practicability of this method. Under the writer’s supervision two localities were rid of mosquitoes by the use of kerosene alone. It will, however, probably not prove feasible to treat in this way the large sea marshes along the coast where mosquitoes breed in hordes, although even here the remedy may prove to be practicable under certain conditions and in certain situations. In inland places, however, where the mosquito supply is derived from comparatively cir- cumscribed pools, the kerosene remedy will prove most useful. In some California towns, we are informed, the pit or vault behind water- closets is subject to flushing with water during the irrigation of the land near by.