Therevidae. 145 



the black, not marked abdomen in the male, and by the spots on 

 the abdomen in the female. 



T. arcuata is very rare in Denmark, I detected it first in 1907 

 when I caught 6 specimens at Copenhagen on the wall at Christians- 

 havn, on the SS""^ and 29^^ August; the specimens were taken on 

 Urtica. 



Geographical distribution: — Europe down to southern Italy; it 

 seems to have its northern limit in Denmark. 



4. T. piebeja L. 



1761. Linn. Fn. Suec. 1779 [Musca). — 1842. Zett. Dipt. Scand. I, 

 204, 2 et 1849. VIII, 2983, 2. — 1862. Schin. F. A. I, 166. - 1903. 

 Kat. palåarkt. Dipt. II, 210. — T. lugens, 1847. Loew, Dipt. Beitr. II, 15,9. 



Male. Frons and face brownish yellow pruinose; the hairs on 

 ihe frons and to a great extent down the cheeks black, towards the 

 mouth aperture yellow or greyish yellow to whitish. Occiput yellowish 

 with yellow or dark greyish hairs; occipito-orbital bristles black; the 

 hairs on the vertex brownish black. Antennæ blackish, the first joint 

 somewhat greyish, the first two joints with black and some yellowish 

 hairs. Thorax black, sometimes slightly brownish ; two slightly lighter 

 stripes are generally just visible as very faint traces, in the middle 

 there is as a rule a narrow stripe of a very deep black colour. The 

 disc densely clothed with erect, black hairs and less densely with 

 somewhat decumbent hairs of a dirty yellowish or more greyish colour, 

 the clothing of the disc thus on the whole of a dark appearance; 

 more rarely the decumbent hairs are bright yellow. I always found 

 two dorsocentral bristles. Sterna and pleura g^*ey with yellow hairs, 

 or the hairs are blackish yellow above, paler or whitish below. 

 Abdomen black, the second and following segments at the hind 

 margin with a narrow, ashgrey, transverse band which is broadened 

 towards the sides and thus almost forms a transverse triangle at 

 each side meeting in the middle. The hind margins of the segments 

 bright yellowish white or nearly white, especially with the light from 

 behind. Abdomen on the dorsal side clothed with chiefly blackish 

 hairs, only towards the sides and at the hind margin of the first 

 segment the hairs may be more or less yellow, but they are often 

 all black. Venter dark grey with broad, pale yellow hind margins 

 to the segments; it is somewhat sparingly clothed with long hairs 

 which are more or less deep yellow to greyish white or whitish. 

 Genitalia chiefly black with ferrugineous hairs at the apex. Legs with 

 the femora blackish, tibia yellow with brownish black tips, tarsi yellow, 

 brownish black towards the end. Goxæ, anterior femora and the 



Diptera Danica. II. 10 



