lop a brood, the malarial mosquito requires much longer--two or
three months--for the full completion of her development. It is,
therefore, a simple problem for an individual householder to search out
the pools which remain filled with water for a period of two months, and
either stock them with fish, drain them entirely, or coat them with
kerosene. No hesitation need be felt about the result of this treatment.
It will positively eliminate all malaria in the vicinity if the work is
thoroughly done.

_Limitation of mosquito infection._

The distance that the malarial mosquito can fly is of interest as
indicating the distance which one must go from a house, hunting for
available pools. All mosquitoes are unable to fly against the wind, so
that, as already noted, one side of a swamp may be comparatively free
from malaria, while the other side may be overrun with it, merely on
account of the direction of the prevailing winds. Some mosquitoes that
breed in salt marshes may be carried for miles, so that a land breeze
will bring millions of the pests to seashore cottages which, with a sea
breeze, are quite free from them. The anopheles has a habit of clinging
to weeds, shrubs, and bushes when the wind blows, so that it is seldom
carried more than about two hundred yards from the place where it is
hatched. If all pools of water, therefore, within this radius are
disposed of, the elimination of malaria will logically follow.

If one is obliged to be in a region where malaria is common, the disease
can be avoided absolutely by protecting one's self from mosquitoes, and
since the anopheles prefer the early morning and evening hours, it is at
those times of the day particularly when precautions must be taken. It
was once thought that the night air caused malaria, and this had some
foundation in fact, because it is in the early evening that the
anopheles is on the wing. By staying in the house after sundown and by
carefully screening the doors and windows, one may live in a malarial
country with perfect immunity. Volunteers have lived for months in the
worst malarial regions in the world without a trace of the disease, the
only precaution being to keep the doors and windows screened and to
prevent mosquitoes from biting.

An interesting experiment was made some years ago by sending a malarial
mosquito by mail from Italy to England, where an enthusiast allowed
himself to be bitten by the insect. He had had no trace of malaria
bef