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Examination
of mosquitoes.
For the proper examination and identification of adult mosquitoes a low
power microscope is almost a necessity, but in the absence of this it will be
found that most of the markings and characters, except those relating to the
shape of the scales, can be made out, though less easily, with a hand-lens.
For the examination under a microscope, the mosquito, which has
already been mounted on a card-disc in the manner above described, is
fixed by a pin thrust through the edge of the disc to a flat piece of cork
about an inch square. This cork is placed on the microscope stage and can
be moved about at will, so as to bring all parts of the mosquito under the lens.
The different parts of the external anatomy which the student must
learn to recognise are shown in Plate III. It is best to begin by examining the
antennae, proboscis, and palpi, because it is by the examination of these
structures that one can tell firstly whether the mosquito is a male or female,
and secondly whether it belongs to the sub-family Anophelinc or not.
To ascertain the sex of a mosquito examine the antenn. In male
mosquitoes the antenn are covered with long hairs so that each antenna
forms a feather-like tuft in front of the head. In female mosquitoes the
antenn have no long hairs and are nearly bare. (Plate IV, h. and f.)
The sex is often obvious to the naked eye when, for example, the
abdomen is distended with eggs or with blood. It is important to make no
mistake in the sex of a mosquito because since only female mosquitoes suck
blood they are the only ones which can carry malaria parasites and the only
ones which we need to study.
To ascertain whether a mosquito is an Anopheline examine the antenn,
the proboscis and the palpi-
(1) Examine the antenn to make sure that the specimen is a female.
(The student of tropical medicine need not complicate the
subject by dealing with male mosquitoes.)
(2) Examine (a) the proboscis and (b) the palpi. If the proboscis is
straight and the palpi are as long or nearly as long as the pro-
boscis the mosquito must be an Anopheline.
These two characters, namely, a straight proboscis and palpi as long or
nearly as long as the proboscis, are present in the females of no other kind
of mosquito than an Anopheline.