226 



Tachinidae. 



second antennal joint and bending horizontally oiitwards; outwards 

 to the upper frontals there are about three reclinate bristles. Orbits 

 with black hairs only on upper half; cheeks distinctly hairy above 

 besides the row of bristles. Antennæ as in campestris but third joint 

 still longer. Palpi black. Thorax coloured and haired 

 as in campestris but no distinct acrostichals present. 

 Abdomen likewise coloured as in campestris but the 

 side spots larger so that three longitudinal lines are 

 formed connected at the black hind margins; third 

 segment with only two bristles and fourth with the row 

 more or less incomplete. Legs black; middle tibiæ with- 

 out ventral bristle; front tarsi at apex of first joint 

 and the three next on posterior side with a little longish, 

 somewhat curled hairs, but this formation also often 

 wanting, so that here a peculiar dimorphism is present. 

 Wings as in campestris. Squamulæ dirty whitish with a 

 yellow margin. H alteres dark yellow or brownish 

 yellow. 



Female. Similar but the frons not specially distin- 

 guished; orbits greyish, downwards more silvery, the 

 frontal bristles normally developed. Orbits broad, 

 the frontal stripe about as broad as the orbits. Fourth 

 abdominal segment with only two marginal bristles. 

 Middle tibiæ as in male without ventral bristle. 

 Length 5 — 7,5 mm. 



M. leucocephala is very common in Denmark all over 

 the country on suitable localities, such as sandy piaces in woods as well 

 as outside, often near shores; the males, w^hen swarming, form a 

 pretty sight with their glistening silvery fore-head. The dates are 

 ^"/g to the first days of August. I have taken it in copula on ^Jq and 

 ^^Z,. The species is recorded from nests of Bembex rostrata, Halictus 

 sexcinctus and Philantus triangulum. 



Geographical distribution: — Europe; towards the north to 

 northern Scandinavia, in Lapland and Finland. It also occurs in North 

 America, where it is recorded from Halictus pruinosus. 



Remarks: The species is no doubt identical with Musca labiata 

 Fabr. and should bear this name. The description leaves scarcely any 

 doubt, and in the collection of Tonder Lund and Sehested there is a 

 male specimen, and as this collection is determined by Fabricius, 

 the specimen may be considered a co-type; as the specimen is not 



Fig. 66. 

 M. leuco- 

 cephala ^ , 

 right front 

 tarsus from 

 above ; from 

 a specimen 



with 

 ornamented 

 front tarsi. 



