6o B R I T I S H B L O O D - S U C K I N G F L I E S
5 . angustitarsis is less common in Britain than the allied S. latipes and
auretim, and has so far been found only in the southern, south-eastern and
midland counties of Eng l and and Wales.
The larvae occur in weedy rivers with only a moderate current, in company
with other species such as 5 . ornaturn, S. erythrocephalum and 5 . equinum,
but in smaller number s ; they are rarely found in small s t reams .
There are no records of the feeding habits of this species.
Si inul ium equinum Linnaeus
The unusually large simple claws, and the presence of three narrow dark
lines forming a trident or somewhat lyre-shaped ma rk on the thorax, are two
features peculiar to this species and the nearly related 5 . salopiense ; in newly
hatched specimens, however, the dark lines tend to be obscured by the golden
pubescence which covers the thorax as well as the abdomen, and moreover the
lines may not be very distinct in dark specimens. The legs in 5 . equinwn are
mainly blackish, only a little yellowish about the knees. The pleural membr ane
is rather densely clothed with whitish pubescence, another feature which this
species shares with salopiense and in which it differs f rom all other British
Simidiu7n except S. ornahi7n.
S. equinu77i is an abundant species in many parts of Eng l and (especially,
perhaps , in the eastern counties) and has also been recorded f rom Wales
(Ll andr indod Wells), Scot land (Ea s t Lothian) and Ireland (County Clare and
County Wexford) , but so far as known at present it does not occur in the
highlands of Scot land.
The activities of this tiy are only too well-known to agriculturists and horsekeepers
owing to its habit of sucking blood f rom the ears of horses, and to a
less extent of cattle ; in the neighbourhood of its breeding places the ears of
horses when not protected by ear-caps may sometimes be seen to have their
inner surfaces covered with a close-packed " pile " of 5 . equinum, and these
at tacks may give rise to severe ulceration. 5 . equi^ium seems to be the only
species of the genus (and indeed the only blood-sucking fly) in Britain which
has this habit, and it at tacks the ears almost exclusively. Only occasionally
does it bite man.
The larvae of S. equinum are found in rivers with a slow or moderate
current, and almost always on water-plants such as Ranunculus, Scirpus, or
Potamogeton, usually in company with 5 . erythrocephalum or sometimes 5 .
ornaturn or 5 . reptans. The females have been observed to crawl under water
to a depth of several inches to lay their e g g s on submerged vegetation or sticks.
There are two or three generations dur ing the year, the adults being most
numerous in April, July and September ; the adults of the spr ing generation
are larger.
Petersen (1924) records 5 . equinum as at tacking the ears of cattle and
sheep as well as horses, and states that the flies actually mate in the ears of the
host.
N E M A T O C E R A — S I M U L I I D A E 6 i
Simul ium salopiense Edwards
( F i g . 23)
The female of this species, not hitherto described in detail, is so similar to
that of the related 5 . equimim that differentiation between them is not easy.
Since the original description was published more ample material has become
available, f rom which it appea r s that the female of 6". salopiense, apa r t f rom
being smaller than that of equinum, differs in having the ground-colour of
the thorax lighter greyish, with the ma rkings more distinct and the front ends
of the three narrow dark lines more distinctly enlarged into spots, and the
tibiae much more extensively pale towards the base.
FIG 2 3 .—Mmu i i um saiopzense Edw.
Tho r a x of if f rom above.
FIG. 2 4 .—S imu l i um ornaturn Mg .
Tho r a x of ii? f rom in front.
The following records for the occurrence of this species in Britain are now
available : HANTS : River Te s t * ; Mins tead, Ringwood. SALOP : River
Severn near Shrewsbury. HEREFORD : River Wye near Hereford ( / . 5 .
Steward). WiLTS. : River Avon near Chippenham {F. T. K. Pentelow).
There are no records of blood-sucking by this species, but its habits are
probably similar to those of 5'. equinum.
As in the case of equinum the larvae are found on subme rged water pl ant s
in rivers of moderate current
Simul ium ornatum Meigen
( F i g s . 20, 24, a n d P l a t e 15)
Thi s belongs to a small group of species which are characteristised (in the
female sex) by having large silvery-grey patches on the shoulders, the rest of
the thorax being dull greenish-black ; the silvery-grey patches each include a
transverse dull black ma rk which when viewed f rom behind becomes silvery,
* In describing this species f rom adul t s only, I sugge s t ed the possibility that a p u p a found by Mosely
in tlie River Tes t and figured by me (Bull. Ent . Res , 11, 236) a s a variety of equinum mi ght be that
of 6'. salopictise. Thi s has now been establis'hed a s correct by St ewa rd and Pentelow, who have reared
salopiense in number s f rom pupa e .