Dexia. 269 



abdomen unicolorous grey; three sternopleural bristles and 



three intraalar bristles (generally) 1. rustica. 



Male with middle stripe on abdomen narrower, incised or inter- 

 rupted at the incisures ; f ourth segment with. black hind margin ; 

 f emale with abdomen black with silver-grey front bands ; gener- 

 ally two sternopleural bristles, and only two intraalar bristles. . 2. vacua. 



1. D. rustica Fabr. 



1781. Fabr. Spec. Ins. II, 440, 26 et 1805. Syst. Antl. 296, 64 (Musca). — 

 1826. Meig. Syst. Beschr. V, 46, 22. — 1844. Zett. Dipt. Scand. III, 1264, 2 

 et 1849. VIII, 3263, 2. — 1862. Schin. F. A. I, 560. — 1889. B. B. Denkschr. 

 Akad. Wiss. Wien, LVI, 120. — 1896. Pand. Eev. Entom. XV, 160, 10. — 1907. 

 Kat. palåarkt. Dipt. III, 445. — 1921. Baer, Zeitschr. f. angew. Entom. VII, 

 380. — 1924. Stein, Arch. f. Naturgesch. 90, 6, 238, 1. 



Male. Frons narrow; head yellow pruinose, jowls partly red in 

 some views; frontal stripe brown. Orbits bare; jowls only with hairs 

 behind. Occiput yellow pruinose, with black hairs and yellow hairs 

 below, Antennæ yellow, third joint about twice to nearly thrice as 

 long as second. Palpi yellow. Thorax yellowish or greyish yellow 

 pruinose, with four dark brown stripes, the median narrow, abbre- 

 viated behind, the lateral interrupted at the suture into an anterior 

 smali and a posterior elongated spot. Scutellum more or less yellow on 

 apical part. Thorax black-haired; two anterior præ- and two posterior 

 postsutural acrostichals ; two to three posthumeral and three intraalar 

 bristles. Three sternopleural bristles. Abdomen yellow with a grey 

 middle stripe in the whole length, whitish or yellow pruinose all over; 

 it is black-haired, with discai and marginal bristles; second segment 

 without bristles, third with one, sometimes two pairs of discai and a 

 pair of marginal, and fourth likewise, but with a row of marginal. 

 Fifth sternite cleft to base. Genitalia somewhat small; upper forceps 

 claw-like, narrow, curved upwards; arms of lower forceps similar 

 but broader, of the same length. Legs yellow, tarsi brownish to 

 black. Wings yellowish brown tinged; veins brown; apical cross-vein 

 rather concave outwards. Squamulæ brownish yellow. H alteres 

 yellow. 



Female. Frons broad; jowls broader than in male, almost as 

 broad as the eye is high. Abdomen all grey and thus the female of a 

 darker aspect than the male; the discai bristles less developed or 

 quite wanting. Wings sometimes darker than in male. 



Length 7 — 12 mm. 



D. rustica is not rare in Denmark; Ordrup Mose, Dyrehaven, 



