Empididae. 277 



on the shore, slipping along very swiftly in it. These differences 

 were, to be sure, not absolute, but however very marked. Most species 

 seem to be widely distributed, down into iSorth Africa. The species 

 are certainly strong robbers, which is indicated by their very power- 

 ful mouth parts. 



Of the genus 8 species are known from the palæarctic region ; 5 

 are found in Denmark, but of these one species is here described as 

 new, the total number of species thus increasing to 9. 



Tahle of Species. 



1. Colour light gvey; wings miik-white 5. incana. 



— Colour dark grey or blackish; wings not milk-white 2. 



2. Wings small, not longer than abdomen 4. arenaria. 



— Wings of ordinary size, longer than abdomen 3. 



3. Halteres more or less pale; hind femora with bristles; largest 



species (3 — 4 mm.) 1 . hirta. 



— Halteres dark ; hind femora without bristles (except the apical 



one); smaller species (1,8 — 2,4 mm.) 4. 



4. Legs somewhat greyish pruinose, middle tibiæ without bristles; 

 radial vein terminating mucli nearer to the apex of the 



subcostal than to the apex of the cubital vein 2. cursitans. 



— Legs somewhat shining, middle tibiæ with some bristles; 

 radial vein terminating in the middle between the apex of 



the subcostal and cubital vein 3. difficilis. 



1. Ch. hirta Waik. 



1836. Walk. Entom. Mag. III, 180 {Tachypeza). — 1903. Kat. palaarkt. 

 Dipt. II, 278. 



Male. Frons and vertex greyish black; seen from in front the 

 frons is grey; epistoma blackish grey; palpi black with black bristles. 

 Occiput black, a little greyish, with four long bristles above, and 

 otherwise with short, black bristles. Antennæ black. Thorax black, 

 slightly greyish pruinose and slightly shining. There are short, biserial 

 acrostichal bristles, separated by a bare interstice from the somewhat 

 long, uniserial dorsocentral bristles; outwards to these latter the disc 

 is clothed with short hairs, and the dorsocentral bristles can only be 

 discerned from these by their length. A humeral bristle, a post- 

 humeral, some notopleural, a supraalar and a postalar bristle present; 

 all hairs and bristles black. Scutellum with two black marginal bristles. 

 Pleura black, somewhat greyish pruinose, above the middle coxæ a 

 slrongly shining, polished black spot. Abdomen black, a little greyish 

 pruinose and slightly shining; it has short, black hairs, which are a 

 little longer at the hind margin of the eighth segment. Venter coloured 

 and haired in the same way. Exterior genitalia large, the ventral 



