252 Syrphidae. 



The species of Didea are very beautiful flies; Schiner mentions 

 that they are more commonly seen on leaves somewhat high over 

 the ground, than on flowers, but I have taken nearly all my speci- 

 mens on humid meadows or in more dry districts in or near woods 

 on flowers of Umbeliiferæ and Gompositæ. The species are nowhere 

 common. 



Of the genus 3 species are known from the palæarctic region, 

 all 3 also occurring in Denmark. 



Tahle of Species. 



1 . Abdominal bands greenish and somewhat narrow ; the loop 

 of the cubital vein rather shallow; epistoma with a short, 

 black middle line ; scutellum nearly all black-haired ; ab- 



domen in the female without spots on fifth segment .... 1. alneti. 



— Abdominal bands yellow and rather broad ; the loop of the 

 cubital vein deep ; scutellum more or less yellow-haired ; 

 abdomen in the female with a band on fifth segment 2. 



2. Epistoma without black middle fine; balteres with the knob 

 yellow ; scutellum yellow-haired or with more or fewer black 

 hairs on the apical part; black middle line on the frons of 



the female reaching more or less distinctly to the antennæ 2. fasciata. 



— Epistoma with black middle line ; balteres blackish; scutellum 

 with black hairs on the apical part; black middie line on 



the frons of the female stopping well before the antennæ 3. intermedia. 



1. D. alneti Fall. 



1817. Fall. Dipt. Suec. Syrph. 38, 4 {Scaeva). — 1822. Meig. Syst. 

 Beschr. III, 310, 54 [Syrjjhus). — 1843. Zett. Dipt. Scand. II, 700, 2 et 1849. 

 VIII, 3131,2 (Scaeva). — 1862. Schin. F. A. I, 314. — 1901. Verr. Brit. 

 Fl. VIII, 326, 1, figs. 269-271. — 1907. Kat. palåarkt. Dipt. III, 54. — 

 Syrphus pellucidulus Meig. 1822. Syst. Beschr. III, 311, 55. 



Male. Frons yellow with a more or less distinet black or brownish 

 spot above each antenna. Epistoma yellow, slightly pruinose, the 

 mouth edge black and this colour extends up and includes the central 

 knob. Jowls grey. Vertex and frons black-haired, epistoma yellow- 

 haired. Occiput yellowish grey pruinose, with yellow hairs. Eyes 

 thinly and short-haired with pale hairs. Antennæ black. Thorax dark 

 æneous, shining; on the sides above the wing-root it is yellowish; it 

 is haired with erect, yellow hairs, among which more or fewer black 

 hairs, generally forming a band across the middle. Scutellum brownish, 

 somewhat translucent with bluish reflections, especially towards the 

 margin; it is black-haired but with some yellow hairs at the base. 

 Pleura with longish, pale yellow hairs. Abdomen velvet black, the 

 hind margin of third segment and the apex shining; there are three 



