i8 BRITISH BLOOD-SUCKING FLIES
NEMATOCERA—CULICIDAE 19
According to available records T. alaskaensis seems to be not uncommon
in Scotland, in both the lowlands and the highlands. In England it has only
been taken (and that sparingly) in Cumberland, Westmorland, and North-West
Yorkshire.
Nothing is at present known regarding the life-history or habits of T.
alaskaensis in this country.
Theobaldia fumipennis Stephens
In this species the conspicuous markings characteristic of T. annulata and
its allies are lacking : there are no spots on the wings and no short white stripe
on the second abdominal segment ; the pale rings on the legs are so much less
conspicuous that the insect might at first sight be mistaken for a large Culex
pipiens, owing to its general brown colouring and banded abdomen ; in T.
juniipennis, however, there are definite though not very broad pale rings on
all the tarsi, these rings being yellowish in colour and spreading across both
sides of each of the joints. The thorax shows four narrow lines of pale scales,
The scales on the middle third of the proboscis are mainly pale except on the
upper surface.
T. ftimipemiis is localty common throughout Britain, having been recorded
from as far north as Inveran in Sutherland, but is easily overlooked owing to
its inoffensiveness : there is no record of the females biting human beings or
domestic animals or even of entering houses ; they will not feed on blood in
the laboratory, neither have any blood-fed females ever been captured.
The eggs of T. fuviipennis are laid singly or in small groups either in driedup
hollows or above the water-level in partly-filled ones ; they hatch in the early
winter and often become full-grown by November, changing to pupae in the
following spring. The adults hatch in April and may be found on the wing
until September.
Theobaldia morsitans Theobald
This closely resembles T. fumipennis, differing most obviously (in the
female sex) in having the proboscis almost entirely dark below as well as above.
T. morsitans is as widely distributed in England as T. fumipennis, and in
most districts it is the commoner insect ; it has been found also in Wales and
Ireland, but there appear to be no well-authenticated records at present from
Scotland.
The habits and life history of T. morsitans are similar to those of T. fumipennis
; the name morsitans is inappropriate as there are no certain records
of its biting in this country.
Theobaldia litorea Shute
This is extremely similar to T. fumipennis and T. morsitans, differing (in
the female sex) from the former chiefly in the more indistinct tarsal rings, and
from the latter in having the proboscis largely pale beneath in the middle.
T. litorea is a much more local insect than either of its two allies ; most of
the records of its occurrence are from the south and east coast (Dorset, Hants,
Kent, Essex) and it has also been found near Belfast and in the fens near
Cambridge.
In habits and life-history, T. litorea resembles T. fumipennis and T.
fnorsitans.
Genus CULEX Linnaeus
The one positive feature of the genus Culex, by which it may be distinguished,
in the adult state, from other genera of mosquitoes, is the presence
of a pair of small hairy pads (pulvilli) between the claws, but as even some
entomologists find this character rather difficult to appreciate, it is not to be
expected that the layman, for whom these notes are intended, will readily
recognise the genus by this means. An easier means of diagnosing our common
Culex is by the negative distinction of the absence of any striking ornament.
Culex is mainly a genus of the tropics and subtropics, only a very few species
extendmg into northern Europe, of which we have two (or three, if C. molestus
be admitted as a distinct species) in Britain. In all cases the eggs are deposited
in rafts on the surface of water, and there are two or more generations in the
year.
Culex pipiens Linnaeus and C. molestus Forskal
(The House-gnats) (Plate 14)
The house-gnats are rather dull-coloured insects lacking any very striking
peculiarities. Nevertheless their identification is rarely a matter of any difficulty
because, apart from the highly-ornamented Theobaldia annulata, they
are the only cuhcme mosquitoes commonly found indoors in this country Doubt
is only hkely to occur regarding the identity of specimens found out of doors
which might easily be confused with dark-legged species of the genus Aedes
such as ^ . punctor or ^ . detritus. From these species house-gnats may usually
be known at a glance by the more reddish-brown tint of the body, due partly
o the colour of the scales, but more to the paler tint of the almost bare sides of
tne tnorax. A more careful examination will show that in Culex the abdomen
IS blunt-tipped, and the upper fork-cell of the wing has a very short stem, this
latter feature bemg diagnostic. The upper surface of the abdomen is mainly
dark brown, each segment having a creamy-white band at the base
belonged f supposed that the common house-gnats of this country
i s h e ? i f ' but intensive research has now established
the fact that there are two distinct forms (Marshall and Staley 19, 0
2 I lL ^9 3 8 ) as distinct specie!
i n e o ror , " " ^^ ^^e sake of consistency the
q S wl '' subspecies only, as has been done by Jobling
show to be " . : (.) the two forms have been
unce a n o w, ^ ' "^^^^er-breeding in the laboratory (though it is still
nceitain to what extent the hybrids are fertile) ; (¿) there are no constant