The Health bulletin [serial] - University of North Carolina at Chapel Hill

30 The Health Bulletin August, 191.
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MALARIA
By C. C. BASS, M.D.
Malaria is carried by mosquitoes.
Almost everybody now knows that,
but there are certain facts connected
with the habits of these insects and
their bearing on the transmission of
malaria that ought to be much better
known. If they were, persons who
have malaria would be more interested
in getting rid of it.
There are almost a hundred different
kinds of mosquitoes in this
country. Of these only about four
and practically only two (Anopheles)
carry malaria. The others are harmless
as far as transmission of malaria
is concerned, but of course, not in
other particulars.
Different kinds of mosquitoes have
different natural habits as to flight,
feeding and breeding. Some habits
of the mosquitoes that carry malaria
are important in this connection and
determine their efficiency as malaria
carriers.
Mosquito Must Have Blood Meal
While certain species of mosquitoes
are thoroughly domesticated and
breed and live near by or in residences,
those that carry malaria are
more wild and spend most of their
time under cover of dense vegetation
such as swamps, rank growth of
grass, weeds and vines. The larval
stage—the "wiggle tail" stage—is
passed in suitable pools or collections
of water. These, the female mosquito
selects by natural instinct to deposit
her eggs in. They are generallypretty
well surrounded and covered
by vegetation, usually swampy
growth.
After the insect develops wings and
is able to fly, the females soon reach
the stage at which they produce eggs
and in this way reproduce and perpetuate
the species. But it is necessarv
for them to obtain a blood meal
before they will develop eggs. If we
rear mosquitoes in captivity and keep
them in cages, not allowing them to
get blood, they never produce eggs.
But let one of them get one blood
meal and she develops and lays eggs
within a few days. The blood meal
that provides the necessary animal
protein is essential, therefore, for reproduction
and perpetuation of the
species—a function which nature always
provides for, in all living things.
It is interesting in this connection
to note that only female mosquitoes
bite. Males have not the necessary
"bill" with which to puncture the
skin and draw blood. Persons are
apt to think that, if this is so, all
the mosquitoes around them must be
females.
Perhaps the female mosquito spends
a day or two near the place in which
she was reared, but when she reaches
the stage at which she needs a blood
meal she flies in one direction or another
in search of some animal or a
man from which she can obtain it.
Some of them seem to prefer animals,
but others accept or even select man
by preference.
The kind of mosquitoes that carry
malaria do most of their feeding after
sundown. In fact, they bite mostly in
the dark in or around the house and
do not venture into a well-lighted
room. Much of the malaria transmission,
therefore, takes place while
the victim is in bed and asleep. After
feeding, the mosquito may remain
around the house for two or three
days or longer, hiding in some dark
place during the daytime and perhaps
coming out and taking another meal
at night.
After a few days she has developed
her eggs and the time has arrived
to lay them. Natural instinct not
only leads her to deposit them on