5 6 BR I T I S H BLOOD-SUCKING FLIES
Another case of transmission of Onchocerca by Simulium has been brought to
light by J. S. Steward (1934, 1937), who showed that O. gutturosa, a parasite
found in the brisket of cattle, is carried by S. ornatum Mg. in England ; in
this case, however, the parasite causes no serious injury.
Apparently only one case is established of a protozoal disease being carried
by Simulium, O'Roke (1934) having stated that 5. venustum Say, carries a
malaria-like disease of ducks (caused by Leucocytozoon anatis) in Michigan.
As repellants against the bite of Simulium on cattle or horses various
mixtures have been recommended, of which the following are examples :
(a) Marlatt (1934) advises a 5 per cent, emulsion of pine tar oil. This is
said to be effective, but when the insects are abundant and in hot weather,
from two to iive applications per day may be needed.
ib) Baranoff (1934) advises a mixture of three parts of rectified kerosene
with ten parts of yellow vaseline. One ounce of this ointment per horse or
cow applied in the morning is said to remain effective all through the day.
For use on the human skin the repellants recommended against midges
(p. 30) will probably be found equally effective against the attacks oi Simulium.
The British species of Sifmdium were reviewed by Edwards (191S and 1920),
seventeen species being then recognised, a total which was subsequently (1927)
increased by two. No further additions have been made, and the following
keys and notes are mainly compiled from the papers cited. For further information,
especially regarding the males, larvae and pupae, reference may be
made to these papers and to the more detailed description of the early stages
by Furi (1925).
K E Y FOR IDENTIFICATION OF THE BRITISH SIMULIIDAE.
(Females only)
1. Wings (fig. 21, a) with an extra vein (R2 + 3) present and with fine hairs only on costal
margin ; second hind tarsal segment simple ; body and legs dark hirtipes Fries
Wings (fig. 21, b) with vein R2H-3 absent, and with minute spinules mixed with the hairs
on costal margin 2
2. Front tarsi (fig. 22, c, d) slender and cylindrical ; front tibiae dark, or not obviously silvery ;
abdomen dull at tip ; base of radial vein hairy 3
Front tarsi (fig. 22, e,f) more or less flattened (compressed) ; front tibiae silvery on outer
surface ; abdomen with tip shining ; base of radial vein bare 11
3. Hind tarsi (fig. 22, a) with second segment simple, without trace of excavation at base ;
hair of thorax erect ; body and legs dark tredecimatum Y^Avt.
Hind tarsi (cf. fig. 22, b) with second segment more or less deeply excavated above near
base; hair of thorax decumbent 4
4. Claws (fig. 22, c) of normal size, each with a thumb-like projection at the base ; integument
of thorax dark, without stripes ; pleurae bare 5
Claws (fig. 22, d) much larger than usual and without projection at base ; integument of
thorax more greyish, with three narrow dark lines ; first segment of hind tarsus largely
yellow ; pleural membrane with a patch of hairs 10
5. Legs entirely blackish ; pubescence of abdomen dull whitish 6
Legs partly yellowish ; pubescence of both thorax and abdomen bright golden and dense. . 9
6. Pubescence of thorax whitish, or partly brownish ; second segment of hind tarsus only
slightly excavated at base above ; eyes closer together than usual 7
Pubescence of thorax golden ; second segment of hind tarsus very distinctly excavated at
base above ; eyes wider apart 8
N E M A T O C E R A — S I M U L I I D A E 57
7. Pubescence of thorax all pale subexcisu?n Edw.
12
13
14
15
16
17
Pubescence of thorax with three dark stripes yerburyi Edw.
8. Larger species (wing 4-4-5 mm.) ; pubescence of abdomen dense costatum Fried.
Smaller species (wing barely 3-5 mm.) ; pubescence of abdomen very scanty ; abdomen
in life i^tip,^ Mg.
9. Femora and tibiae clear yellow, with black tips aureum Fries
Femora and tibiae darker, the latter with a dark ring close to the base, .angustitarsis Lundst.
10. Larger (wing 3-4 mm.) ; thorax and legs darker equinum L.
Smaller (wing 2-2-5 mm.) ; thorax and legs paler salopiense Edw.
11. Frons (above antennae) and face (below antennae) grey, dull ; shoulders with white markings
(fig. 24) J 2
Frons blackish, shining (face usually grey) 14
Front and middle femora mainly yellow variegatum Mg.
Femora mainly dark
Pleural membrane with soft hairs ; claws with a small sharp tooth near middle.. ornatum Mg.
Pleural membrane bare ; claws not toothed itoUeri Fried.
Shoulders marked as in 5. ornaiu7n ; claws toothed ¡5
Markings on shoulder different, or absent ; claws simple 16
Pleural membrane with soft hairs ornatum var. fiitidifrons Edw.
Pleural membrane bare monticola Fried.
Face black, shmmg, like the frons ; legs mainly black tuberosum Lundst.
Face grey ; legs more extensively pale
. Thorax almost dull, with coarser pubescence jg
Thorax somewhat shining, with much finer pubescence 20
. Basal two-thirds of hind tibia clear yellow (hind femora almost all black, contrasting with
the yellow base of tibia) reptans L.
Basal half of hind tibia yellow, but less sharply distinguished from the black apical
portion
Rather less than basal half of middle tibia yellowish venustum Say.
Rather more than half of middle tibiae yellowish morsitans Edw'
20. Thorax rather brightly shining ; front coxae reddish erythrocephalumVxfg.
Thorax less shining, with traces of two greyish longitudinal stripes ; front coxae blackish
erythrocephalu77i form sericatum Mg.
Simulium hirtipes Fries
One of the largest of the British Simuliidae, and the only representative in
this country of the subgenus Prosijnulium, sometimes regarded as a genus
distinct from Simulium, owing to the pecularities of structure mentioned in
the key. The body and legs are uniformly dull blackish and clothed with dull
yellowish pubescence.
hirtipes is chiefly a mountain species, being widely spread in the Scottish
Highlands from Perth to Sutherland. It is doubtful if the species occurs in
England ; an isolated record from Crowborough, Sussex, requires confirmation
as it may have been due to an error in labelling. The occurrence of the species
m North America has now been definitely established (Twinn, 1936), and it
has also been found in Eastern Siberia (Rubzov).
According to the late J. W. Yerbury this is " the earliest of the biting pests
of Scodand," the adults appearing in May ; though common in some localities.
It IS not known to be abundant enough anywhere in Britain to be a serious pest'
It is recorded by Dorogostaisky, Rubzov and Vlasenko as a severe bloodsucker
in Eastern Siberia, attacking man, cattle, and other animals.
19