458 Descriptions of British Diptera. 
bands ; antennae black, the base of the terminal joint sometimes 
yellowish, the two lower joints not very hairy, and varying some- 
what in their relative proportions : * palpi and hypostome light ash- 
grey, the latter with black points at the sides, and four remote black 
spots towards the middle, two of them deeply impressed, and placed 
at the lower end of the vertical line ; forehead grey, with a smooth 
shining-black space just over the antennae, two velvety-black round- 
ed spots behind it, and a smaller one in the middle ; the latter 
sometimes obsolete : thorax blackish-brown, with greyish- white lon- 
gitudinal lines, some of them having a whitish spot near the mid- 
dle ; sides of the breast ash-grey, hairy : abdomen dark brown, the 
hinder margin of the segments, a dorsal line, and a series of faint 
spots on each side, light grey j on each segment, beside the lateral 
spots, there is a short oblique line of small impressed points : un- 
der side brownish-grey ; thighs grey ; tibiae black, reddish-yellow 
at the base in the anterior legs, and encircled with two broad rings 
of that colour in the others ; tarsi black, the radical joint reddish- 
yellow at the base, except in the fore-legs : halteres yellowish - 
white, the knob with a brown spot : wings greyish-brown, with a 
dark stigmatic spot, the surface variegated with numerous whitish 
spots and undulating lines, many of them circular, and one of them 
forming a short transverse band near the apex. (Fig. 3.) 
Male : eyes greyish-green, the lower part purplish-brown, with 
undulating yellowish lines : forehead consisting of a small triangu- 
lar space, on which there is a callosity, and a grey dot : thorax and 
abdomen with similar markings to those of the female, the three 
first segments of the abdomen spotted at the outer side with tawny 
yellow. 
This insect occurs in great plenty throughout Britain and Ire- 
land. In Scotland it is called the Cleg, or Gleg, a term derived from 
the Danish word klaeg. It is by far the most troublesome of the Ta- 
banidse, both on account of its numbers, and its persevering and 
incessant attacks. The great variations in the proportions of the 
joints of the antennae, have been thought to indicate distinction of 
species, and several have accordingly been established. But this 
circumstance alone is obviously insufficient, in this instance, to be 
assumed as a satisfactory proof of specific difference, for the varia- 
tions seem to be almost without end. Thus, the H. equorum of 
* The radical joint has frequently a constriction towards the apex, sometimes 
so strongly marked as to present the appearance of a separate articulation. It 
was no doubt this circumstance that deceived Reaumur, and led him to represent 
the antennae as 4-jointed. See Vol. iv. pi. 18, fig. 2. 
