hawks have long been
known as great enemies of mosquitoes, and they certainly do destroy many
of them as they are hawking about places where mosquitoes abound. Dr.
J.B. Smith of New Jersey very much doubts their efficiency, but
observations made by other scientific men would seem to indicate that
they often devour large numbers of mosquitoes during the course of the
day and evening.

Spiders and toads destroy a few mosquitoes each night. Certain external
and internal parasites destroy a few more, but the sum total of all of
these agencies is probably not very considerable, for while the adults
may have several natural enemies they are not of sufficient importance
to have any appreciable effect on the number of mosquitoes in a badly
infested region.

ENEMIES OF THE LARVAE AND PUPAE

The larvae and pupae on the other hand have many important enemies. Indeed
under favorable conditions these may keep small ponds or lakes quite
free from the pests. The predaceous aquatic larvae of many insects feed
freely on wrigglers. The larvae of the diving beetles which are known as
water-tigers are particularly ferocious and will soon destroy all the
wrigglers in ponds where they are present (Fig. 92). Dragon-fly larvae
also feed freely on mosquito larvae. Whirligig beetles are said to be
particularly destructive to _Anopheles_ larvae and many other insects
such as water-boatmen, back-swimmers, etc., feed on the larvae of various
species. A few of these introduced into a breeding-jar with _Anopheles_
larvae will soon destroy all of them, even the very young bugs attacking
larvae much larger than themselves.

It is interesting to note that the larvae of some mosquitoes are
themselves predaceous and feed freely on the other wrigglers that may
chance to be in the same locality.

[Illustration: FIG. 90--The young (nymph) of a dragon-fly. (From
Kellogg's Amer. Insects.)]

[Illustration: FIG. 91--The cast skin (exuvae) of a dragon-fly nymph.]

[Illustration: FIG. 92--Diving-beetles and back-swimmers. (From
Kellogg's Amer. Insects.)]

Various species of fish are, however, the most important enemies of the
mosquitoes. Great schools of tide-water minnows (Fig. 93) are often
carried over the low salt-marshes by the extreme high-tides and left in
the hundreds of tide pools as the tide recedes. No mosquitoes can breed
in a pool thus stocked with these fish. In the fresh-water streams and
lakes there are several species of the top-minnow