Melanostoma. 231 



tinged, most on the anterior part. Squamulæ dirty whitish, with 

 a whitish or yellowish fringe. Halteres with the knob more or less 

 darl^ened. 



Female. Vertex and frons broad, bluish or somewhat purplish, 

 shining, the latter with small side dust spots. Epistoma greyish 

 pruinose and more densely than in the male. Vertex with black, 

 frons with yellow hairs; epistoma with short, pale hairs. Antennæ 

 longer than in the male, especially the third joint longer. Thorax 

 shining, with short hairs. Abdomen not similar to that in the male; 

 it is dull black, with ciirious, dark purplish, shining, but not very con- 

 spicuous markings; the markings consist of a pair of large spots on 

 second segment close to the front margin; on third and fourth seg- 

 ments the spots are similar but united to a band from which a nar- 

 row prolongation goes to the hind margin; the hind margin of the 

 fourth segment and the fifth and foUowing segments are quite shining; 

 abdomen may accordingly also be described as dark purplish, shining, 

 with a middle line and hind margin on second segment dull black, 

 and with dull black, transverse spots at or near the hind margins of 

 third and fourth segments. Legs much paler than in the male, the 

 anterior quite pale with only the apical part of tibiæ and the tarsi 

 more or less darkened ; hind femora with a broad, black ring and the 

 tibiæ with the base yellow. The legs are short-haired, and the hairs 

 all pale. 



Length 6,5 to about 7,5 mm, the female the larger. 



The above description of the male is made from specimens from 

 Greenland; in Danish specimens probably the legs would be some- 

 what paler. (I may here note, that M. ambiguum from Greenland is 

 doubtful in so far as the female of it differs a little from European 

 ambiguum, see Stæger 1. c. and Lundbeck 1. c). 



This species is at once known from the other two Danish species ; 

 it is no doubt the species which (together with duhium and fimhriatum) 

 on account of its specially haired anterior legs in the male, the broader 

 head with the antennæ placed rather high, and the larger fifth ab- 

 dominal segment in the male stands nearest to Platychirus. 



M. ambiguum seems to be very rare in Denmark, we have only 

 two specimens, both females, taken in Hillerød in a garden in this 

 year (1915) on ^^/s. It is a spring species, and it will probably be found 

 more common, when sought for in spring. 



Geographical distribution: — Northern and middle Europe down, 

 into Gorsica; towards the north to middle Sweden; further it occurs 

 in Greenland, and according to Verrall also in North America. 



