Vol 10 Part 14. An introduction to the immature stages of British Flies ...

epresented by a single genus (Anopheles) with 5 species, and Culicinae, with 5 genera
and 27 species. Larvae of the two subfamilies found in Britain may be distinguished as
follows:
Eighth abdominal segment without an elongate dorsal siphon (fig. 43), larvae resting
horizontal to the water surface . . . . . . . . . . . . . . Anophelinae
Eighth abdominal segment with a dorsal siphon which is longer than broad (fig. 44), larvae
resting obliquely to the surface . . . . . . . . . . . . . . . Culicinae
The final stage (fourth ins tar) larvae of the British species are keyed by Snow ( 1984);
Cranston et al. ( 1987) provide keys to fourth ins tar larvae, pupae and adults.
All mosquito larvae are aquatic but occur in a variety of habitats and ecologically
may be referred to four groups.
I. Domestic species (adults overwinter indoors): Anopheles atroparvus van Thiel (brackish
water), A. messeae Falleroni (permanent ponds, slow streams), Culiseta ( = Theobaldia)
annulata Schrank (foul or brackish water in stagnant ponds, tanks. waterbutts, etc.),
Culex pipiens L. typical form (natural and artificial collections of fresh, foul or brackish
water), C. pipiens form molestus Forskal (usually in water below ground level in semi
darkness).
2. Salt-marsh species (on or near coasts): Aedes caspius Pallas (brackish water, also in sewage
effluents), A . detritus (Haliday) (brackish or saline water), A. dorsalis (Meigen) (brackish
water).
3. Arboreal species (tree-holes): Anopheles plumbeus Stephens, Aedes geniculatus (Oiivier),
Orthopodomyia pulcripalpis (Rondani).
4. Rural species (non-domestic, in ground waters usually away from coasts): all the remaining
species.
Some species on the British List have only been recorded once or twice, but because
of their medical importance are worthy of further attention. Aedes aegypti (L.) is the
principal vector of urban yellow fever abroad and although temperature requirements
preclude it from becoming established in Britain under natural conditions, there was a
local outbreak of yellow fever in Swansea in 1865, almost certainly from a single
generation introduced from a ship. The species is extensively cultured in laboratories
and escapes may occur. Larvae of Anopheles algeriensis Theobald have been recorded
only once from three localities in Norfolk where they occurred (and persisted for some
years) in extensive shallow puddles among thick sedges on the marshes adjoining
Hickling Broad. This species is doubtfully indigenous but investigations by a resident
in the area would be worthwhile as it is one of the species capable of transmitting
malaria and the disease used to occur in East Anglia. The species has recently been
discovered in Anglesey (Morgan, 1987). Locally contracted cases of malaria can still
occur in the U.K. in the vicinity of airports when mosquitoes are inadvertantly
imported in aircraft. Aedes leucomelas Meigen has only been recorded once from
Britain (Widmerpool, Notts, May 1919) and Culex modestus Ficalbi has only been
recorded in 1944-1945 in the Portsmouth area.
Apart from these 'exotic' species there is still much to be learned about the larvae of
most mosquitoes, especially on their precise feeding habits and distribution.
The larvae of Anopheles collect their food at the surface and of Culicines below the
water surface. Two different methods of feeding are adopted: by nibbling algae, dead
leaves, etc. (e.g. Aedes, except A. cinereus Meigen) or by movements of the mouth
brushes (figs 43, 44, br) which create a whirlpool bringing floating organic particles into
the mouth (remaining genera and species).
Mattingly (1969) has drawn attention to the interesting problem of mouthbrush
polymorphism and particle size of food taken, which can apparently vary during a
life-history and requires further investigation.
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