154 Orthorrhapha brachycera. 



and this no doubt holds good also for the other species, the larvæ 

 living in the sand at the horders of lalces and at the shore. 



The species of J'achytrechus occur exclusively at the horders of 

 lakes, and at the shore, and they are seen running on the sand quite 

 near to the water, and flying low, often in great numbers. I have 

 seen them fly upon other flies as in attack, but I have never seen 

 any specimen with prey. 



Of the genus 15 species are known from the palæarctic region; 

 3 have hitherto been found in Denmark. No doubt two species more, 

 consobrinus Walk. and ripicola Loew, will be found in our country. 



Tahle of Species. 



1. Front metatarsi in the male about as long as the four 

 following joints ; middle femora in both sexes short-haired 

 below, or with long hairs on the basal part ; all tibiæ with 



the apex black 2. 



— Front metatarsi in the male twice as long as the four 

 following joints ; middle femora in both sexes with longish 

 hairs below in the whole length; anterior tibiæ quite 



yellow 3. insignis. 



2. Middle femora yellow for the greatest part, with long hairs 

 below on the basal half; hind tarsi pale at the base; 

 posterior cross-vein curved, discai bend not nearer to it 

 than to the apex; in the male the outer lamellæ of the 

 hypopygium much longer than broad 1. ammohates. 



— Middle femora with only the apex yellow, without long 

 hairs below; hind tarsi quite black; posterior cross-vein 

 straight, discai bend nearer to it than to the apex; in 



the male the outer lamellæ short, not longer than broad 2, notatiis. 



1. T. ammobates Walk. 



1851. Walk. Insect. Brit. I, 173, 40. (Dolichopus). — 1862. Schin. 

 F. A. I, 204.— 1903. Kat. palåarkt. Dipt. II, 306. — Dolichopus plumipes 

 Fall. (nec Scop.) 1823. Dipt. Suec. Dol. 14, 13. — 1843. Zett. Dipt. Scand. 

 II, 619, 107, et 1859. XIII, 5070, 107. — Ammobates plumipes 1831. 

 Stann. Isis 1831, 268, 1. — 1842. Stæg. Krøyer's Tidsskr. IV, 9, 1. 



Male. Vertex and frons brown pruinose. Epistoma white, some- 

 v^hat silvery. Palpi dark, light grey pruinose. Occiput æneous, a 

 little pruinose ; postocular bristles yellov^ below, black above. Antennæ 

 a little elongated, about as long as the head, third joint longer than 

 broad, very convex below, more straight above, the point truncate or 

 rounded, lying dorsally but very slightly marked, the whole apex 

 being nearly rounded; the antennæ are black, the basal joint yellow 

 below or quite yellow. Thorax olive, somewhat æneous or a little 



