Helophilus. 463 



9. H. transfugus L. 



1758. Linn. Syst. Nat. X, 594 et 1767. XII, % 987, 52 et 1761. Fn. 

 Suec. 1818 {Musca). — 1822. Meig. Syst. Beschr. III, 371,13 Tab. XXXII, 

 Fig. 8. — 1843. Zett. Dipt. Scand. II, 682, 6 et 1849. VIII, 3123, 6. - 

 1862. Schin. F. A. I, 342. — 1901. Verr. Brit. Fl. VIII, 542, 7, figs. 374- 

 375. — 1907. Kat. palåarkt. Dipt. III, 112. — 1910. Beck. Bed. ent. Zeitschr. 

 LV, 229. 



Male. Vertex and frons considerably narrower than in lunulatus; 

 vertex brownish yellow pruinose, blackish about the ocelli; between 

 vertex and frons a narrow, blackish brown, slightly angular line; frons 

 a little paler pruinose ; epistoma whitish yellow pruinose, without bare 

 spot or stripe, the lower lateral parts black and shining but grey 

 pruinose downwards ; jowls grey pruinose. Vertex black-haired, yellow- 

 haired posteriorly; the hairs on frons mixed black and yellow to quite 

 yellow; epistoma with long, yellow hairs. The epistoma shaped as in 

 lunulatus but narrower and more widening downwards. Occiput grey 

 pruinose, yellowish above and here with a dark spot or streak at each 

 side behind the eye-margin; the hairs whitish below, yellow above, 

 and no black hairs at the eye-margin. Antennæ with the basal joints 

 brownish to blackish, third joint yellowish brown or reddish brown, 

 arista darker. Thorax brownish black, dull, with two narrow, yellow 

 or brownish yellow stripes and with the side margins rather indefmitely 

 brownish ; the middle stripes widen inwardly behind, in front of scutel- 

 lum and are here often confluent to a somewhat greyish space ; along 

 the middle of the disc is a very fine, more or less distinct and com- 

 plete line. Thorax is clothed with longish, yellow hairs. Scutellum 

 yellowish brown, darker at the base and the basal corners, with long, 

 yellow hairs and more or fewer black hairs on the disc. Pleura 

 greyish or brownish grey pruinose, with yellow hairs. Abdomen nar- 

 row, much narrower than in lunulatus, dull black, a little shining at 

 the hind margins of second and third segments; first segment a little 

 greyish in the middle; second greyish or yellowish at the sides from 

 the base to the middle and here sending a whitish grey, deeply curved 

 lunule inwards and forwards ; third segment marked in the same way 

 but the pale colour at the sides produced to the hind margin and 

 forming small spots at the hind corners; the lunules on the segments 

 are widely separated in the middle and sometimes they are almost 

 separated from the sides; both the segments have a more or less 

 distinct, greyish or glaucous triangle in the middle on the shining hind 

 margin; the fourth segment has similar but more shallow lunules and 

 all the side margins and the hind margin greyish yellow, at the hind 



