(15)
How to collect adult anopheletes.
One of the habits of anopheles mosquitoes is that they only
fly about after dusk and during the night; in the daytime they
seek some dark shed, outhouse, or stable, where they rest on the
walls and roof, until evening. In these places they can be easily
caught, the necessary implements being a few dry test tubes and a
large dry bottle. When a mosquito is seen sitting on the wall or
roof, the mouth of a test tube is placed very gently over it. It will
fly into the tube, the mouth of which can then be closed with a plug
of cotton wool. As each mosquito is caught it may be transferred
to the large glass bottle by placing the mouth of the tube over that
of the bottle and removing the cotton wool plug. The mosquito
will fly into the large bottle and the tube can be used again. If
anopheletes are at all abundant twenty or thirty can be caught in
this way in a very short time. The best places in which to search
for them are outhouses, cowsheds, woodsheds, and thatched un-
occupied rooms with dirty smoke-blackened walls and many cob-
webs. It is almost useless to search in a new whitewashed house.
Even in places which appear favourable, mosquitoes are often difficult
to detect, and some species hide among the straw of a thatched roof
or in holes and corners of the wall with great success. For search-
ing the roof a ladder should be used, so that the eye is not more
than a foot or so off the roof, and every part of the thatch should
be carefully examined. The commoner anopheletes are light coloured
and stand out against the black background of dirt and soot like
little white thorns hanging from the roof, but even an experienced
observer may sometimes miss the small brown species which, as we
shall see, are so important from the point of view of malaria.
How to mount and examine anopheletes.
The mosquitoes that have been caught should be killed by placing
a drop or two of chloroform on the muslin cover of the bottle. The
dead mosquitoes are then turned out on to a clean white sheet of
paper and mounted as quickly as possible.
The following articles are necessary for mounting a mosquito:-
(1) A supply of fine silver pins, No. 20 size.
(2) A pair of forceps for holding the pins.
(3) Small discs of thin cardboard.