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 ; 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- 

 banidae, 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 lias 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. 



