258 BACOT : MOSQUITOES AND THE DANGER OF MALARIA.
no record of the intensity of the mosquito population when
Ague was prevalent. In the future, however, it may enable us
to state that there is no danger of Malaria, even in districts
where Anopheles mosquitoes are present, unless their numbers
reach a certain level.
V.—The Breeding Places of Mosquitoes.
As already pointed out, there is a broad general divergence
between the places most suitable for Anopheles mosquitoes and
those of other groups. The former, as typified by A.
maculipennis, keep more to open sunlit water than do
the majority of the non-Anophelene species. An important
fact to remember in either case is that small, impermanent,
and very shallow collections of water, or waters which are much
obstructed or clogged with weeds, require much more careful
attention as breeding places than do larger, freer, and more
permanent pools or streams. The reason for this is that the
latter are tenanted by enemies of the mosquito larvae, which
are usually few or wanting in the small, impermanent, or shallow
waters. It is true that we find .4. maculipennis in rivers and
permanent ponds, though as a rule Culicina larvae are very
scarce in such waters ; but the chances of their survival to the
adult stage are small in comparison with those present in grass-
grown ditches, running swamps, or the hoof-holes of cattle
on the soft margin of a pond or stream. Of course, they are
more easily seen in open water, and the larger collections of
water are more easily found and charted, but they are less
dangerous.
This will be at once apparent if we consider the natural
enemies of the mosquito, which are many. In the air bats,
birds, dragon flies, wasps, and predaceous dipterous flies, all
take a very heavy toll of the adults when upon the wing ; while,
when at rest, not only do some of these still persist in their
attacks, but numerous other animals join in. Lizards, toads,
and frogs snap them up; ants, spiders, and (abroad) scorpions
prey upon them, both in and out of doors. Ants, by reason
of their omnipresence, are, in the tropics, very formidable com-
petitors of the spiders ; which in temperate climes are probably
the chief foes of resting mosquitoes. The dangers amid which
the adult mosquito is forced to rest are instanced by the continual