1. THEREVA 571 



on the sides and on the liindmargin ; second segment with a narrow but 

 obvious yellowish hindmarginal hem, and the third segment with a still 

 narrower and less obvious one ; on the following segments the extremely 

 narrow hems are hardly obvious ; on the second segment there is a greyish 

 white cross-band immediately before the hindmarginal hem which is excised 

 in an arch in the middle, so that it becomes quickly broader from the middle 

 outwards but then from the end of the arched incision extends to the side- 

 margin in considerable, but almost equal breadth ; the third segment has a 

 similar, but somewhat narrower band, on which the arched incision is not so 

 sharply defined towards the sides, as the band distinctly widens from its end 

 ou.t to the sidemargins. The same applies in an even greater extent to the 

 band on the fourth segment, which again is rather narrower than the one on 

 the third ; the fifth and sixth segments have a somewhat broader greyish 

 white cross-band, which is not very sharply defined anteriorly and is only 

 indistinctly excised on the middle, and not widened at the sides ; the seventh 

 and eighth segments are altogether shining black. Belly ashy grey; the 

 front segments rather paler than the hind ones ; the seconcl and third 

 segments have a quite distinct very dirty whitish, but the following segments 

 not clearly perceptible, hindmarginal hem ; also the pale band which lies 

 quite at the side of the abdomen, and which connects the hindmarginal hems 

 with each other is at least on the anterior segments very distinct. The 

 pubescence is whitish on the upper side of the basal segment, on the sides 

 and on the cross-band of the second and third segments, and also on the 

 underside of the three basal segments, but black and depressed on the black 

 marking of the second and third segments, on the fourth and all subsequent 

 segments it consists of short, erect black hairs on the sides. The femora are 

 black with short whitish pubescence ; the tibiae are more rusty yellow than 

 rusty brownish, and the tip of the front pair to a small extent, of the middle 

 and hind pairs scarcely blackened ; tarsi black, the basal half of the first 

 joint of the_ front pair, and the greater part of the first joint and the base of 

 the second joint of the middle and hind pairs brown. Halteres dark brown, 

 with the middle of the stem paler. Wings hyaline with a brownish tinge, 

 veins dark brown, more rusty brown at the base and f oremargin ; stigma 

 brown. 



Length about 11-5 mm. 



This species is not very generally known though probably dis- 

 tributed over a wide area, and but few students have known it in both 

 sexes. The male may be distinguished from T. pleieia by its larger size 

 and more universally black pubescence, while the female should be dis- 

 tinguished by its much smaller frontal callus. 



T. circumscripta has not previously been recorded as British, but 

 Colonel Yerbury took a male at Lyndhurst on June 16, 1897, and since 

 I distinguished that specimen I have seen another male in the Entomological 

 Club collection mixed up with specimens of T. nohilitata, and I think the 

 fragments of a male taken by Colonel Yerbury at Nairn on June 4, 1905, 

 belong to this species but the pale pubescence on all parts of the thorax 

 is whitish grey while that on the head is grey rather than brownish 

 yellow. If T. circumscripta and T. ttrsina are synonyms this species is 

 recorded from Lapland to South France and from Central Europe. 



Synonymy. — This species was probably first described by Schummel in 1838 under 

 the name of T. frontalis^ but his description is very uncertain and there was 

 already a T. frontalis of Say. Loew in 1846 described the female under the name 

 of T. circumscripta and Wahlberg in 1854 probably described both sexes under the 

 n&m.Q oiT.tirsina. Kowarz in 1883 called attention to T. ^lrsina being the male 

 of T. circumscripta., but Bezzi in Kertesz's Katalog retains the two as distinct 

 species; if they should be distinct we must adopt the name of T. ursina for 

 the British species. Wahlberg's diagnosis of the female of T. ursina is as follows : 

 " cinerascens opaca brevius et remotius hirsuta supra grisea pilis nigris intermixtis 



