BACOT : MOSQUITOES AND THE DANGER OF MALARIA. 249
resemblance to Anopheles maculipennis, by reason of the spots
on its wings, though it belongs to the Culicidae. This insect
must be distinguished with care from the much more dangerous
species.
Just as all the available evidence points to Anopheles
mosquitoes as being alone responsible for Malaria, so also does
it point to certain Culicina as the sole responsible agents
in the case of yellow and dengue fevers—the former being
definitely proved as due to the presence of Stegomyia fasciata ;
while the latter, though formerly thought to be due to Culex
fatigans, is now said to be conveyed by the same mosquito as
yellow fever, C. fatigans is, however, definitely incriminated
as conveying Filaria bancrofti, the causative agent of elephan-
tiasis. There is, in the case of this disease, evidence which
suggests that certain Anopheles mosquitoes, as well as Stego-
myia fasciata, may also be incriminated ; for the embryonic
forms of the worms which block the lymphatics and thus cause
the characteristic swellings are found occasionally in the thoracic
muscles of these mosquitoes.
As we are concerned in this country only with Malaria (or,
to use its old English name, "Ague"), I do not propose to
deal further with these other diseases, but will confine myself
to the incidence of Malaria and the mosquitoes which convey
it, and will conclude with some general remarks on the local
distribution of mosquitoes and on methods for their control.
The eggs of Anopheles mosquitoes are deposited singly (Pl. vi.,
1 and 2). Although they may collect into small groups on
the water-surface, they are never cemented together into rafts.
They can be distinguished at once from those of all other tribes
of mosquitoes by their side frills or floats. Generally, if not
always, they float until hatched and are unable, so far as is
known, to resist desiccation or defer hatching after incubation,
as do the eggs of the yellow fever mosquito and its relatives.
The larvae (Pl. vi.—3 and 4) may be distinguished at once
hy the fact that they have no syphon tube, and that, when at
the surface of the water, they rest in a horizontal position,
while the larvae of other tribes hang head downwards by their
syphon tubes in a more or less vertical or oblique position,
further distinguishing features are the star-shaped processes (Pl.
vi., 5), a pair of which are present on the dorsal area of the