BRITISH BLOOD-SUCKING FLIES
some variation in this respect. Some specimens examined have the anal
area of the wing bare (fig. 48 a), but a few (all from Sway, Hants), taken on
robin and hedge-sparrow, have a narrow stripe of fine hairs in this area
(fig. 48
Genus HIPPOBOSCA Linnaeus
Hippobosca equina L.
(The Forest Fly) (Plate 39)
As indicated by the English name, the principal home of this species in the
British Isles is in the New Forest, in Hampshire, where it may often be seen
in bee-hke clusters, sometimes numbering many hundreds, on the ponies and
cattle which run wild there. The flies chiefly congregate on parts where the
skin is thinnest, beneath the tail, on the perinaeum, and on the inner surfaces of
the thighs. The bite does not seem to cause pain, and the animals bred in the
forest take no notice of the fly, but strange horses and especially donkeys are
sometimes driven almost frantic by the irritation caused by a single Forest Fly
crawling over them. The toothed claws enable the fly to cling so tightly to
the hair that it is impossible for an animal to dislodge it by a brush from its
tail, and the quick and somewhat crablike movements of the insect, which
when disturbed usually moves sideways, tickle the host and are exceedingly
irritating to sensitive animals.
The Forest Fly is on the wing from May till October, and while it appears
to be commonest in the south of England it has been taken as far north as
Aberdeen. It occurs in Europe and many other parts of the world to some of
which it was no doubt carried on horses taken thither by man.
Genus ORNITHOPONUS Aldrich
Ornithoponus ardeae Macq.
This insect, which is found in Europe on the heron and its allies, has only
been taken once in the British Isles. The unique specimen was taken on a
dead purple heron, an occasional visitor to the British Isles, in Pembrokeshire
in 1932.
It is of the same general appearance as Hippobosca equina, from which,
however, it may easily be distinguished by the absence of the wrinkles on the
wings and other characters alluded to in the key, apart from the difference of
host.
Genus STENEPTERYX Leach
Stenepteryx hirundinis L.
(Plate 42)
In the British Isles this insect is usually found on martins and more rarely
on swallows and swifts. It is incapable of flight, its wings being reduced in
size and non-functional.
CYCLORRHAPHA- HIPPOBOSCIDAE 123
It is found throughout Europe and its range is probably co-extensive with
that of its host, though it probably cannot maintain itself outside the nesting
area of the host bird.
Captured martins, especially fledglings, may have a very large number of
these parasites crawling about on them. There do not appear to be any records
of the adult insect being taken at times of the year when the martins are away,
but dormant pupae, in which form the insect survives the winter, have been
taken in old nests.
Genus CRATAERHINA v. Olfers
Crataerhina pallida Latr.
(Plate 43)
While this insect is sometimes found on swallows, martins and some other
birds, the swift is undoubtedly its true host.
As is the case with Stenepteryx hirundinis very little is known of its lifehistory
and habits. The adult insect is to be taken on swifts, particularly
newly flown fledglings, during June and July in the British Isles. It is fairly
active and like Steriepteryx hirundinis it may occasionally be found in houses,
having crawled thither from the nest of its host. The possibility of its ever
attacking a human being is remote. The species survives the winter as a
dormant pupa in the hosts' disused nests.
Genus MELOPHAGUS
Melophagus ovinus L.
(The Sheep Ked, " Sheep Tick", " Sheep Louse") (Plate 45, Fig. 2)
A higher degree of adaptation to a parasitic existence is exhibited by this
species than by any of the foregoing members of the Hippoboscidae, since the
wings are entirely wanting in both sexes and the halteres are absent. This
peculiarity, coupled with the general strangeness of its appearance, which
presents little resemblance to an ordinary fly, and the fact that it passes its
whole life-cycle in the wool of the sheep, has gained for the insect two of the
popular names mentioned above. When seen in the fleece of the sheep these
insects give the impression of spiders crawling amongst the wool. It is doubtful
if their presence causes any direct harm to the sheep, but the irritation set up
by them if present in large numbers may cause the sheep to rub itself and
resultant abrasions may become infected bv the maggot fly (Lucilia sericata
Mg.).
The adults are long-lived, as are probably most of the Hippoboscidae, and
it has been estimated that the female may live for as long as four months during
which time she may produce 10 to 12 larvae. The larvae pupate immediately
and remain amongst the wool. The puparia are frequently washed out of the
flccce in large numbers when sheep are dipped, but the best method of control
is to store the wool from shorn sheep well away from them and from other sheep.