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CHAPTER IV.
THE MOSQUITOES OP KARACHI—continued.
Section 1.
The Mosquitoes of Karachi.—The Culicid Fauna of Karachi is very limited.
The different species met with are:—
Culicines.
Stegomyiata Fasciata
Culex Fatigans
Culex Concolor
Culex Taeniorhynchus
Theobaldia Spathiapalpis.
Anophelines.
Nyssomyzomyia Rossi
Neocellia Stephensi
Cellia Pulcherima.
By far the commonest is Culex Fatigans and was found everywhere. The
8. Fasciata came in next in extent of distribution, and each of these were
severally proportionate to the permanent and temporary breeding places of the
locality respectively.
Steqomvia Fasciata.
Section 2.
1. The genus Stegomyia is characterised by the head and scuttellum
being entirely clothed with flat scales. S. Fasciata is
the only species found in Karachi. It is essentially a
domestic mosquito living and breeding in the immediate neighbourhood of
houses. It adapts itself readily to all sorts of conditions, provided the water is
stagnant. It is pre-eminently a chatty breeding mosquito here, even clean
and new chatties with clean water being sometimes found full of them. It
cannot possibly be the odour of baked moist earth that attracts them most,
because in Kumbarwadda, i.e., the potter's quarter, where chatties are baked or
made, their larval and adult population differed in no respect from any other
similar quarter, and perhaps it was less still. It does not breed by preference
in dirty or foul water, but can adapt itself readily under necessity to all sorts
and conditions of life, e.g., wells, garden tanks, tubs smeared with coal tar,
cess-pits, etc. Their presence in cess-pits can only be accounted for by their
being transferred from an original receptacle, as when this cess-pit water was
bottled, they died either from development of foul gases or a thick film of
fungus on surface of water.
2. Larvae.—The larvae are somewhat elongate with rudimentary anten-
nae and a short stout syphon. They are of a creamy white colour and darken
later to a pale brown tinge, when they are about to change into pupae. The
intestinal canal can always be made out by the naked eye as a dark line in
the body. Their movements are sluggish and wriggling, and they pass a
greater part of their time in browsing at the bottom. At the surface they hang
limp down almost vertical, or go round and round the receptacle by wormlike
movements. The size of the larva differs according to the quantity and nature
of food available, and the greater of it there was, they became plump and
opaque white, suggesting almost a fungus growth on their body. I am
inclined to believe that they live entirely on dead organic matter—vegetable or
animal—and were never observed to touch unicellular living organisms running
even near their mouth-brushes. Active Vorticella were often seen living and
attached to a part of their body. No definite period can be assigned to the
length of their larval life. In the Laboratory when abundant food was supplied
they turned into Nymphae on the 9th day at the earliest (from the time of the
hatching of eggs) to the 15th. They were observed to moult twice. Under
conditions found outside, the shortest time has been two weeks and the longest
nine weeks; and that, while some of the same breed, attained maturity earlier,
that of others was considerably retarded. Another thing noticed was that the
size of the larva in no way limited that of the adult Imago—small mosquitoes
hatching out of even big larvae and vice versa.