10 BRITISH BLOOD-SUCKING FLIES NEMATOCERA—CULICIDAE I I
most numerous in June. Eggs are laid on the sides of the cavity above the
water-level, so that when the supply of water in the hole is replenished by rain
they are washed down and hatch. The winter is probably passed mainly in
the egg stage as the larvae are able to survive only brief periods of frost. It is
uncertain whether more than one complete life-cycle is passed through during
the year ; the apparent succession of broods during the summer may be due
to irregularities of rate of growth in the larvae or (as is known to happen in
some species of this genus) to delay in hatching of a proportion of the eggs of
one batch.
A. geniculatus can inilict a severe bite and is often troublesome in welltimbered
districts.
Aedes rusticus Rossi
(Plate 9)
This is a rather larger insect than the others of the dark-legged group of
the genus A'édes, the average wing-length being about 6-6-5 mm. as against
5 mm. in A. functor or A. detritus. There is some variation in the ornamentation
of the body ; in many specimens the abdomen of the female shows a more
or less complete median longitudinal stripe of ^^ellowish scales, but in other
examples this stripe is apparent only on the last few segments and may be
reduced to a slight widening of the transverse pale bands (which are present
in all cases). The front half of the thorax shows in perfect specimens a pair of
rather narrow black stripes separated and bordered by golden-brown scales
The sides of the thorax (pleurae) are more densely scaly than usual, and a
feature distinguishing this species from all other members of the genus in
Britain is that the scales on the " posterior pronotum " (immediately below
each shoulder) are all very broad.
A. rusticus is a woodland species common in many parts of England and
Wales ; in Scotland it has been found at Dingwall, Cromarty. The adults
appear chiefly in April and May, less commonly in June and July.
The larvae of yi. rusticus are found for the most part in ditches or woodland
pools which are bordered with deciduous hedges or trees, such pools being
usually bottomed with dead leaves, upon which the larvae feed. The eggs
may hatch, and the larvae grow to maturity, at any time during the winter,
but pupation does not occur until late in March.
Although A. rusticus will bite readily enough in the neighbourhood of its
breeding places, there do not appear to be any records of its causing serious
annoyance, perhaps because other woodland species are usually more abundant.
Aëdes punctor Kirby
(Plate 8)
This species, at one time more commonly known under the name A. fiemorosus,
is the only member of the dark-legged group of the genus Aëdes in which
the pale transverse bands of the abdomen (or at least those on the last few
segments) are constricted in the middle so that their margins form an inverted
V. The vestiture of the thorax is rather variable in colour ; usually it is light
brown with a single broad median stripe of dark brown, but often this stripe
may be absent, or the whole of the back of the thorax may be dark brown ;
occasionally the stripe may be double, or the scales at the sides may be whitish.
The scales of the wings are entirely dark, and there is no sprinkling of white
scales on the dark parts of the legs and abdomen.
A. punctor is an abundant species in many parts of Britain ; it occurs
almost throughout England and Scotland, but is specially associated with sandy
and gravelly districts, and with moorlands with heather, birch and coniferous
woods. It is therefore more abundant towards the north. Adults first appear
in April and may be found throughout the summer.
The females of A. punctor deposit their eggs in dry hollows where water is
likely to collect during the winter, either on open heaths or in woods ; the eggs
are laid above the level of any water that may be temporarily present in the
summer. The larvae hatch when the pools are flooded during the late autumn
or winter and pupate in the following March. Larvae are sometimes also
found during the summer months ; it is thought that these have derived from
eggs, the hatching of which had been delayed, and not that they represent a
second generation.
A. punctor attacks human beings fiercely in the neighbourhood of its
breeding-places (for example, in the southern outskirts of London) and has
sometimes been taken biting indoors in houses in the vicinity.
Aedes sticticus Meigen
This is very similar to A. punctor and A. communis, resembling the latter
in having the pale bands of the abdomen of even width, but differing from both
in the scaling of the mesonotum, which is blackish in the middle, whitish at
the sides (somewhat as in ^ . geniculatus, though the contrast in colours is less
sharp), and in having a whitish stripe on the outer side of the hind tibia.
A. sticticus is a scarce insect m Britain. It was first recorded from Scotland
by Stephens under the name Culex concinnus ; since then it has been found
once in Perthshire, once in Westmorland, and on a few occasions in the New
Forest.
According to continental observers A. sticticus breeds in open or partly
shaded temporary pools ; the winter is passed in the egg stage, and there may
be one or more summer generations if the breeding areas become re-flooded.
The adults are said to travel considerable distances from their breeding places,
often causing widespread annoyance.
Aedes communis De Geer
This is very similar to A. punctor, but the pale bands of the abdomen are
of even width and the front half of the thorax shows two narrow dark stripes.
It has only once been found in Britain, in a wood near Strelley, Notts., in September
1922. The life history in Europe is similar to that oi A. punctor.