572 THEREVID.E 



subtus albida, vertice flavo-griseo callis 2 parvis nigris nitidis parum elevatis 

 in lineam transversam dispositis, thorace cinereo-albido-bivittato, segmentis 

 abdominis basi anguste subnitidis nigris, apice fascia albida opaca ad latera latiori 

 antice medio retusa, 2 ultimis totis nigris nitidis, tibiis rufis, alis hyalinis fusco- 

 nervosis. — Femina callis yerticis parvis in lineam transversam positis, nee callo 

 magno obcordato. Tarsi antici in utroque sexu nigri, vix summa basi rufe- 

 scentes."^ From this it would appear that the frontal callus of his female was 



separated into two spots, and the tarsi in both sexes were more extensively black 



than in my description. 



6. T. bipunctata Meigen. Male with mainly whitish (not briUiant 

 white) pubescence. Female with the frontal callus divided into a pair of 

 spots. Wing-veins very strongly defined when viewed from the wing-tip, 



A rather small species with the pubescence of the male 

 more whitish than in any other British species except T. 

 annulata and T. lunulata but not silvery white as in them, 

 and the frontal callus of the female distinctly divided. 



$ . Face and f rons entirely covered with pale dust ; f rons yellowish grey with its 

 margin darkened in some lights, bearing long moderately dense black 

 pubescence but that on the fore part and all round the base of the antennse 

 composed of rather shorter thinner pale hairs which are slightly bent 

 forwards ; face light grey, with an almost whitish shimmer near the lowest 

 angle of the eyes and on the lower part of the back of the head near the eyes, 

 clothed with dense long rather drooping yellowish white hairs on the middle 

 part but with more or less abundant more erect black hairs near the eye- 

 margins, aiid these black hairs usually forming lateral fringes irregularly three 

 or four hairs wide which extend from the black hairs on the frons to almost 

 the bottom ot the eyes and are followed after a short interval by a small sparse 

 clump of similar black hairs below the eyes, but these fringes of black hairs 

 may extend only about half-way down the face or on the other hand may be 

 five, six, or even seven hairs wide and be practically continued to the sub- 

 ocular black hairs, and sometimes scattered black hairs intermingle with the 

 yellowish white hairs though not to the middle of the face ; under part of the 

 head with long dense dull yellowish white pubescence which amalgamates 

 with similar pubescence on the front coxa3 and becomes conspicuous ; lower 

 part of the back of the head inflated, greyish yellow (except where shimmer- 

 ing white), and bearing moderately long greyish yellow pubescence with a 

 single inconspicuous row of scattered black hairs near the eyes ; upper half 

 of the back of the head hardly inflated and bearing less abundant shorter 

 greyish yellow pubescence, while the postocular black hairs become longer, 

 more numerous (about fifteen), and more conspicuous ; the usual few black 

 bristles on quite the back of the head are almost hidden in the pubescence ; 

 vertex dusted yellowish and bearing moderate black pubescence. Eyes bare, 

 touching for about a quarter the distance between the occiput and the 

 antennte ; facets all practically equal in size. Antennae Avith the two basal 

 joints rather light grey, but the third joint greyish black -brown and some- 

 times a little ferruginous at the base ; first and third joints almost equal in 

 length,_second joint short, and style short ; first joint bearing pale pubescence 

 about its base but stiif black bristles near its end; second joint with very 

 short black bristles ; third joint bare. 



Thorax dull dark greyish brown, often with three or five inconspicuous 

 dark lines down the disc of which the two outside the middle one are more 

 conspicuous than the others and seem by contrast to leave greyish lines inside 

 them ; pubescence on the disc fairly dense but only slightly obscuring the ground 

 colour, composed of mixed black and pale yellowish hairs of which the black 

 hairs are long and erect while the pale hairs are short and depressed ; when 

 viewed from in front the pale hairs become conspicuous but when viewed 

 from behind the black hairs seem to predominate ; towards the sides the pale 

 hairs become longer, denser, and less recumbent and consequently more 



