49 
swarming with the larvee of Culex pungens, C. stimulans, and C. per- 
turbans, also with the larva of an Ephydrid— Brachydeutera argentata 
Walk.—and with the larva of an Ephemerid of the genus Ceenis, and 
other aquatic species. A number of specimens of Hydrophilid larvee 
were found by the writer in this pool. .They fed upon the other 
aquatic insects with avidity, and three of them were placed in a large 
battery jar with about a half gallon of this water, teeming with insect 
life and containing apparently some hundreds of the mosquito larvee 
and many of the others just mentioned. These three Hydrophilid 
larve, in the course of a week, practically devoured all of the other 
animal life in the jar. Only two male mosquitoes and one female suc- 
ceeded in reaching the adult stage. 
No one can realize the intensity of the struggle for existence which 
is going on in a stagnant pool until he forces himself to the seemingly 
rather unpleasant occupation of lying down by its side and watching 
with a large hand lens the various forms of life with which the water 
is swarming. Aside from the larve of the dragon flies and the preda- 
tory larvee of the three great families of aquatic beetles, namely, the 
Dytiscide, the Hydrophilide, and the Gyrinide, there are aquatic 
neuropteroid insects which are predatory and which feed upon 
mosquito larve as well as others, like those of the genus Hydro- 
psyche; and there are aquatic Heteroptera which are also predatory. 
Aside from insects, there are many other natural enemies of mosqui- 
toes. Many fish eat their larve and pupe, and such night-flying birds 
as nighthawks and whip-poor-wills, and bats as well, destroy the adults. 
Harvey (American Naturalist, 1880, p. 896), quoted by Mrs. Aaron, 
found 600 mosquitoes in the crop of a nighthawk. 
REMEDIES AGAINST MOSQUITOES. 
Remedies in houses and the prevention of -bites.—Of the remedies in 
use in houses the burning of pyrethrum powder and the catching of 
mosquitoes on the walls in kerosene cups are probably the best, next 
to a thorough screening and mosquito bars about the bed. In burning 
pyrethrum powder it is well to moisten the powder sufficiently with 
water so that it can be molded roughly into little cones about the size 
of a chocolate drop. ‘These cones are placed on a pan and dried in 
the oven. If ignited at the apex the cones smolder slowly, giving off 
an odor not unlike that of the prepared punk which boys in this 
country use to light firecrackers. Two or three of these cones burned 
in a room in the evening will give relief by stupefying the mosquitoes. 
This smoke appears to be perfectly innocuous to human beings. The 
writer has breathed it evening after evening without the slightest per- 
ceptible ill effect. The method of catching mosquitoes on the walls 
with kerosene in cups is now in frequent use in different parts of the 
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