390 Syrphidae. 



on 2/4, and larvæ and pupæ in Holte at the foot of a Poplar with 

 Cossws-larvæ on ^^Is, they developed in the midst of April (Kryger); 

 finally larvæ were taken in Hillerød in a Poplar in the holes of a 

 Cossus-larva in August, the date of developraent not noted (Godskesen). 

 Geographical distribution: — Europe down into Italy; towards 

 the north to northern Sweden, and in Finland. 



2. B. dorsata Zett. 



1838. Zett. Ins. Lapp. 597,3 et 1843. Dipt. Scand. II, 689,4. — 1862. 

 Schin. F. A. I, 327. — 1907. Kat. palaarkt. Dipt. III, 88. 



Male, This species resembles hicolor but thorax is ferruginous at 

 all events on the pleura, and abdomen has dark markings. Head as 

 in bicolor. Thorax varying from ferruginous to almost quite cinereous, 

 dull, with four darker strlpes, iwo approximated in the middle, a 

 little diverging behind and abbreviated, and two lateral, abbreviated, 

 in front and a little interrupted at the transverse furrow ; when thorax 

 is grey the stripes are blackish, but when thorax is ferruginous the 

 stripes, at all events the lateral, are only somewhat darker. Scutellum 

 ferruginous. The hairs on thorax quite short, ferruginous or brown, 

 and there are the same bristly hairs on thorax and at the margin of 

 scutellum as in hicolor. Pleura ferruginous, sometimes the sterna 

 blackish below; the hairs are longish, yellow, the upper hind corner 

 of mesopleura with a couple of black, bristly hairs. Abdomen reddish 

 yellow, generally with the first segment and the hind margins of the 

 foUowing segments blackish, and with a blackish middle stripe on 

 second segment, stretching more or less in on the third. The hairs 

 short, yellow or mainly yellow. Venter yellow. Legs as in bicolor, 

 reddish, the last joints of tarsi blackish, front and hind tarsi quite 

 darkened ; the legs are haired quite as in bicolor, hind femora likewise 

 black setulose below. Wings yellowish or a little brownish tinged, 

 the venation as in bicolor. Squamulæ whitish with a yellow fringe. 

 Halteres yellow. 



Female. Vertex and frons yellow, dull, above the antennæ a 

 shining space; the hairs short, pale. Occiput almost quite reddish, 

 only a little grey above. Tarsi paler on the basal part than in the 

 male; hind femora below only haired, not setulose. 



Length 6—6,5 mm. 



B. dorsata is very rare in Denmark, we have only two specimens, 

 a male and a female, taken on Falster in earlier time. 



Geographical distribution : — Northern and middle Europe down 

 into Austria and Hungaria; towards the north to northern Sweden, 

 and in Finland. 



