S8 BRI TI SH B LOOD- SUCKING F L I E S
Th e early s t a g e s are found in r apid hill s t re ams ; the l a rva e do not congre -
g a t e in l a r g e ma s s e s , but are scat tered over l a rge stones or on the rocky bot tom
The r e is probably only one generat ion in the year .
Simulium tredecimatum E dwa r d s *
A bl a cki sh species in many respect s re s embl ing S. hirtipes, but with ma r k e d
s t ructural differences as indicated in the key.
Th e occur rence of this species in Br i tain requires conf i rmat ion. Th e only
record at present is the original one of l a rva e t aken " f rom s toma ch of t rout ,
E n g l a n d , " the locality and collector be ing unknown.
5 . tredechnatum ha s been found in No rwa y by Ol s t ad.
Simulium subexcisum Edwa r d s
Anothe r bl a cki sh species with pa le pubescence, superficially r e s embl ing the
last two, but differing in s t ructural details.
5 . subexcisum, though nowhere common, is widely di s t r ibuted in Br i t a in,
having been recorded f rom Hant s , Sus s e x , Devon, He r e ford, Middl e s e x
Her t s . , Ar r an, Invernes s , Na i rn, Suthe r l and. It ha s also been found in C a n a d a
{Twinri).
The r e are no records of the f e eding habi t s of this species. Adul t s a p p e a r
in Apr i l and Ma y . L a r v a e occur in sma l l t empor a ry rills ; owing to the na tur e
of the br e eding places there can only be a s ingle annua l generat ion.
Simulium yerburyi Edwards
Thi s is very s imi lar to 5 . subexcisum, of which it ma y be no more than a
variety.
T h e few known spec imens were t aken in He r t s . (Knebwor th) , Invernes s
(Ne thy Br idg e ) and Na i rn.
L i f e history s imi lar to that of S. subexcisum.
Simulium costatum Friederichs
E x c e p t for the more br a s sy tint of the pubes cence of the thor ax, this l a r g e
Simulium mi ght easily pa s s on a superficial examina t ion for hirtipes,
though its s t ructural features are quite different.
At present 5 . costatum ha s been found in only three places in Br i tain :
Ba r ton, near To r q u a y ; Ba r ton, north-eas t of L u t on ; and Ditchley, Ox on.
It ha s al so been found in Ge rmany and Denma r k , in Cent ral and Ea s t e rn
Siber i a , and ( surpr i s ingly) in the Pa t a g oni an Ande s (Edwa rds , 193 0 ; Pres
uma bl y it will eventually be found to occur acros s the width of Eu r o p e and
As i a and throughout the length of Ame r i c a .
Th e species is at present so little known that there are no records of its
f e eding habi t s in Br i tain, but the l a rva e have been found on stones and leaves
* This species may perhaps be synonymous with pallipes Fries, as suggested by Dorogostaisky,
Rubzov and Vlasenko (1935).
NEMA TOC E R A—S IMUL I I DA E 59
in smal l and fairiy r apid s t r e ams . In Ea s t e rn Sibe r i a it is recorded by Do r o g o -
s tai sky, Ru b z o v and Vl a s enk o as " very widely di s t r ibuted c ommon species .
In s t r e ams and rivers of mode r a t e swi f tnes s . Fr equent ly in g r e a t numbe r s
Severe bl o odsucke r . "
Simulium latipes Meigen
T h o u g h r e s embl ing the five species jus t cons idered in its da r k thor a x and
legs, the f ema l e of 5 . latipes is readi ly di s t ingui shable in life by the pinki sh
colour of the abdomen, which even in per fect spe c imens is only very scant i ly
clothed with fine pa le hai r ; the fine pube s c enc e of the thor a x is br a s sy ins t ead
of whitish.
latipes is a c ommon species throughout E n g l a n d and S cot l and, and is
also recorded f rom I reland, as well as f rom Ca n a d a ; the adul t s are found
chiefly in Apr i l and Ma y .
In spite of its abundanc e , the records of bi t ing by latipes are so few tha t
it cannot be r e g a rded as a pest . It is pos s ible that it bites chiefly bi rds , as do
some nearly related species.
The norma l breeding places of latipes are smal l s t r e ams and rills with
gravel ly bot toms which are l iable to dry up dur ing the s umme r ; only except
ional ly are the l a rva e found in l a rger s t r e ams . The r e is usua l ly only one
brood, though a second brood ma y be ha t ched in Au g u s t if the s t r e ams a r e
still running. Us s i n g records that in De nma r k the e g g s are laid under s tones
in the bed of the s t r e am ; they can wi ths t and drying, though even when the
s t r e am fails in s umme r there is usua l ly some dampne s s unde r the s tones .
Simulium aureum Fries
F ema l e s of this species in per fect condition are resplendent object s , the
ba c k of the thor ax and the whole of the a bdomen be ing densely clothed with
br ight golden scaly pube s c enc e ; when seen in flight they a p p e a r like little
golden balls. The legs are conspi cuous ly par t i -coloured, bl a ck and yellow.
5 . aureum occurs throughout Br i tain and is not at all unc ommon though
easily over iooked ; it is also wide spr e ad in No r th Ame r i c a where it ha s been
known as 5 . bracteatum Coq.
The r e are no records of bloodsucking by this species in Br i t ain, but Be -
qua e r t (1938) s tates that in Nor th Ame r i c a it bites gosHngs ; in Af r i c a a very
s imi lar species ha s been found clus ter ing on the r ump s of fowl s .
Th e life-history of aureum is s imi lar to that of latipes, the l a rva e
occur r ing chiefly in smal l s t r e ams and rills, especial ly those with a s tony or
gravel ly bot tom. The r e ma y be two genera t ions in the year .
Simulium angustitarsis Lundstrom
The r e s embl anc e between this and 5 . atireum is rather close, and the f ema l e s
of the two have been confus ed ; the mos t obvious difference is the pr e s enc e in
this species, and the abs enc e in aureum, of a da rk ring near the ba s e of ea ch
t ibia.