Dolichopodidae. 303 



row of few bristles and one on the anterior side near the base. Wings 

 almost hyaline ; veins black, discai vein parallel with the cubital vein, 

 but with a small curve about in the niiddle of its last part. Squaniulæ 

 yellow, with a yellow fringe. Halteres pale yellow. 



Fig. 95. Antenna of S. leucxirus 9- X 85. From a dried object. 



Female. Epistoma broad, coloured as in the male, and bluish 

 and shining below. Antennæ shorter than in the male, the third 

 joint pointed oval, arista a little longer than the antennæ. 



Length 2,5 to about 3 mm. 



S. leiicurus is rare in Denmark, we have only three specimens, 

 two males and a female, which I bred from a hollow beech at Ørholm. 

 In the beech were larvæ of Xylomyia maculata and on the Vt 1908 I 

 took home a portion of tlie quite loamy decaying wood; in the fol- 

 lowing week came the Si/stenus, but I did not detect the pupæ. 



Geographical distribution: — Northern and middle Europa down 

 into Germany ; it occurs in England, but is not known north of Den- 

 mark. The species is only known from bred specimens. 



IV. Hydrophorinae. 

 19. Acltalciis Loew. 



Species of very sniall size and of not or only slightly melallic, 

 blackish, greyish or yellowish colour. Head about as broad as or 

 a little broader than thorax, somewhat semiglobular. There are 

 ocellar, outer vertical and postvertical bristles, and a pair of small 

 bristles on the posterior side of the ocellar tubercle. The eyes are 

 slightly and short-hairy, almost microscopically; they are separated in 

 both sexes; the epistoma is narrow in both sexes, and only slightly 

 broader in the female than in the male. The postocular bristles form 

 a single row. The antennæ placed near to each other, somewhat 

 above the middle; they are not long, a little longer in the male than 

 in the female; the first joint short, the second small and simple, the 

 third somewhat pointed oval, a little longer in the male than in the 

 female, and in this latter sex less pointed; it has a characteristic 

 shape as the upper margin is convex, the lower straight or nearly so. 



