ON THE BRITISH SPECIES OF SIMULIUM. 



31 



those of *S. ornatum, being somewhat narrowed towards the tip ; external part of 

 adminiculum much longer and narrower, and its internal appendages of different 

 form. Legs black, with the following exceptions : front tibiae with the usual silvery- 

 grey patch ; middle tibiae yellowish on the basal half, with a silvery sheen, especially 

 on the outer side ; hind tibiae pale on the extreme base ; hind metatarsi brownish 

 on the basal half or two-thirds. Front tarsi considerably expanded, more so than in 

 jS. variegatum ; hind metatarsi (fig. 4, c) only slightly enlarged, their diameter being 

 considerably less than that of the tibiae. Front femora not so hairy as those of 

 S. ornatum. 



Fig. 4. Hind tarsi or metatarsal joints of Simulium, X 40 :— a, 8. ornatum^ (^ ; 

 b, S. tuberosum, (^ ; c, 8. reptans, (^ ; d, 8. argyreatum, (J ; e, 8. equinum, 

 (^ or ^ ; f, 8. latipeSf (^ ; g, 8. latipes, $ ; h, S. angustipes, (^ from Nairn ; 



i, 8. Jiirtipes. 



Female. — Head : face with silvery-grey dusting, frons and vertex polished black. 

 Antennae black, the two basal joints often indistinctly reddish. Thorax dull greenish 

 black with large patches of silvery-grey dusting on the shoulders, more conspicuous 

 in certain lights ; these patches however are not distinctly divided by transverse 

 stripes as they are in S. ornatmn ; the whole mesonotum clothed with fine hair-like 

 golden pubescence, more densely so than in the male. Pleurae lacking the patch 

 of soft hairs. Abdomen : hair on basal segment yellow ; second segment more or 

 less yellowish, silvery-grey at the sides ; segments 3-5 dull black, bare ; segments 

 6-8 shining blackish, with fine yellow^ish hair. Legs : front pair with the coxae clear 

 yellow ; femora almost entirely blackish brown ; tibiae yellow, black on the apical 

 fourth, the usual patch of silvery-grey dusting present, but less conspicuous on 

 account of the yellow ground-colour ; tarsi (fig. 3, c) black, very much expanded, con- 

 siderably more so than in the male. Middle and hind legs : coxae black ; femora 

 blackish, except at the extreme base ; tibiae clear yellow on the basal half or 

 two-thirds, black at the apex ; tarsi blackish, base of mid metatarsus yellowish- 

 brown, hind metatarsus clear yellow on the basal half or two- thirds. All the 

 <claws simple, though with well-marked basal enlargement. 



