28 F. W. EDWARDS. 



1. Simulium ornatum, Mg. (figs. 1, 2, 3 and 4). 



Length, 2 -5-4 -5 mm. 



Male. — Antennae all black, as in every other British species. Thorax velvet- 

 black (as in all the species of this group), clothed uniformly and fairly densely with 

 a short, close-lying golden pubescence ; in front with a pair of shimmering silvery 

 spots, narrowly or broadly separated in the middle ; about half only of these spots 

 reflects light at one time ; in certain lights the side and hind margins of the mesonotum 

 are also silvery. Pleurae with a patch of soft hairs between the prothoracic spiracle 

 and the base of the wing, on the area called by Malloch the " membranous patch." 

 These hairs, though very easily rubbed off, provide an important specific character, 

 as there are only two other British species which possess them. Abdomen velvet- 

 black, with the silvery lateral spots on segments 2, 6 and 7 as usual in this group. 

 The long hair on the "basal scale " varies in colour from yellow to black ; long hair 

 is also present along the sides. Genitalia (fig. 1, a) : basal lobe of side-pieces short, the 

 claspers long, strap-shaped, slightly curved, of even width throughout, with a single 

 short spine near the tip on the inner edge. Adminiculum broad, thumb-like. Little 

 or no variation appears to occur in the genitalia of this species ; about 15 specimens 

 were carefully mounted and compared. Legs : front pair black, the tibiae silvery 

 on the outside ; femora clothed rather densely with long black hair, and a few rather 

 long hairs at the tips of the tarsal joints, which are moderately flattened and expanded. 

 Middle and hind legs dark brown to blackish, the basal quarter of the femora, basal 

 third or half of the tibiae, base of the mid metatarsi and basal half or three-fifths of 

 the hind metatarsi, brownish yellow. Hind metatarsus (fig. 4, a) nearly as broad 

 as the tibia. 



Female. — Head entirely dull silvery-grey ; antennae black, the two basal joints 

 usually, but not always reddish. Thorax dull greenish black, with fine golden 

 pubescence as in the male ; in front with large silvery grey lateral patches, which are 

 only narrowly interrupted by ground-colour in the middle, and include a dull black 

 transverse stripe, which when viewed from behind becomes silvery, while the silvery 

 parts become blackish. Pleurae with the same patch of soft hair as in the male. 

 Abdomen with the long hair on the basal segment yellowish ; second segment black 

 above, silvery grey at the sides ; segments 3-5 dull black in the middle, with whitish 

 patches posteriorly on the membranous sides, bare ; segments 6-8 shining, with 

 rather sparse fine yellowish hair. Legs much as in the male, but the enlargement 

 of the front tarsi (fig. 3, a) is rather more noticeable, the hind metatarsi are much less 

 thickened, the front femora are scarcely hairy, and the pale markings, especially of 

 the middle and hind tibiae, are more extensive ; the ground colour of the front 

 tibiae dark ; occasionally the front and middle femora are largely pale, though 

 they are always darkened at least at the tips. All the coxae dark. Claws (fig. 2, a) 

 with a distinct tooth near the base. 



Time of appearance. — The dates of capture of the specimens I have examined range 

 more or less continuously from 13th March to 20th August, though the great majority 

 were taken during April and May. Stray specimens have also been taken in October, 

 and even (in the Channel Islands) at Christmas. 



Distribution. — S. ornatum is probably common everywhere, wherever running 

 water is available, though apparently it is less common towards the north. I have 



