s, sticklebacks (Fig.
94), etc., that feed voraciously on mosquito larvae and unless the grass
or reeds prevent the fish from getting to all parts of the ponds or
lakes very few mosquitoes can breed in places where they are present.

Minute red mites such as attack the house-flies and other insects
sometimes attack adult mosquitoes, but they are rarely very abundant.
Parasitic roundworms attack certain species. Others suffer more or less
from the attacks of various Sporozoan parasites.

FIGHTING MOSQUITOES

When mosquitoes are bothering us we usually begin by trying to kill the
individual pests that are nearest to us. We try to crush them if they
bite us; we screen the doors and windows to keep them from the house. In
warmer countries the people are a little more hospitable and do not
screen the mosquitoes out of the house entirely, but screen the beds for
protection at night, and if the mosquitoes get too insistent during the
day the bed makes a safe and comfortable retreat. All the mosquitoes in
a room may be killed by fumigating with sulphur at the rate of two
pounds to the thousand cubic feet of air-space. Pyrethrum is also used
largely, but it only stupefies the mosquitoes temporarily instead of
killing them. While in that condition they may be swept up and
destroyed.

Various substances are sometimes used as repellants by those who must be
in regions where the mosquitoes are abundant. With many of these,
however, "the cure is worse than the disease." Smudges are often built
to the windward of a house or barn-yard and the smoke from a good
smoldering fire will keep a considerable area quite free from
mosquitoes. The man who can keep himself enveloped in a cloud of tobacco
smoke will not be bothered by mosquitoes. Oil of pennyroyal, oil of tar
or a mixture of these with olive oil, and various other concoctions are
sometimes smeared over the face and hands. These will furnish protection
as long as they last. Dr. Smith says that he has found oil of citronella
quite effective and of course less objectionable than the other things
usually used. Care should be taken not to get it in the eyes. An
ointment made of cedar oil, one ounce; oil of citronella, two ounces;
spirits of camphor, two ounces, is said to make a good repellant and is
effective for a long time.

[Illustration: FIG. 93--Killifish (_Fundulus heteroliatus_). (From
Bull. 47, U.S. Fish Com.)]

[Illustration: FIG. 94--Stickleback (_Apeltes quadracus_)