rther
need of quinine. The general impression that swampy land is favorable
to the development of malaria is correct, but not because the damp air
is itself pernicious. The significance of the damp ground lies solely in
the fact that mosquitoes in one stage of their existence require water
for their development. They breed only in water and always deposit their
eggs in water, on the surface of which the eggs float in very small
layers. The eggs hatch into larvae or wrigglers, which also must remain
in water for development, and it is not until the third stage, that of
the full-grown mosquito, that the animal leaves the water which was his
birthplace. Obviously, therefore, if there is no water there can be no
mosquitoes.

_Elimination of mosquitoes._

Another pertinent fact discovered by scientific research is that the
development of the malarial mosquito is confined to the vicinity of
stagnant pools, because in fresh water, where fish are to be found, the
eggs and larvae of the mosquito are a most acceptable fish food. One of
the most practical ways, therefore, of getting rid of possible
mosquitoes is to make sure that the pond always contains a number of
fish. Woods Hutchinson gives the following interesting description of
the way this fact was discovered:--

"It was early noted that mosquitoes would not breed freely in open
rivers or in large ponds or lakes, but why this should be the case was a
puzzle. One day an enthusiastic mosquito student brought home a number
of eggs of different species, which he had collected from the
neighboring marshes, and put them into his laboratory aquarium for the
sake of watching them develop and identifying their species. The next
morning, when he went to look at them, they had totally disappeared.
Thinking that perhaps the laboratory cat had taken them, and
overlooking a most contented twinkle in the corner of the eyes of the
minnows that inhabited the aquarium, he went out and collected another
series. This time the minnows were ready for him, and before his
astonished eyes promptly pounced on the raft of eggs and swallowed them
whole. Here was the answer at once: mosquitoes would not develop freely
where fish had free access; and this fact is an important weapon in the
crusade for their extermination. If the pond be large enough, all that
is necessary is simply to stock it with any of the local fish,--minnows,
killies, perch, dace, bass,--and presto! the mosquitoes practically