Acanthocnema Becker, 1894

Sinclair, Bradley J., 2025, Revision of the Nearctic species of Acanthocnema Becker, 1894 (Diptera: Scathophagidae), European Journal of Taxonomy 1026, pp. 304-337 : 334-335

Key to Nearctic species of Acanthocnema Becker, 1894

1. Anterior orbital seta proclinate, posterior 2 orbital setae more or less lateroclinate ( Fig. 43); yellowish to pale greyish species; at least base of postpedicel yellow ( Figs 4, 21, 29, 35, 41) ........................ 2

– All 3 orbital setae lateroclinate ( Figs 14, 50); dark greyish species, with dark postpedicel ( Figs 16, 49) ..................................................................................................................................................... 7

2. Proepimeral seta absent ( Fig. 42) .............................................................. A. ruficauda Curran, 1929

– Proepimeral seta present ( Fig. 6) ...................................................................................................... 3

3. Fore femur without spine-like posteroventral setae on basal half ( Figs 4, 21); wing with clouding about crossveins ( Figs 7, 22) ............................................................................................................ 4

– Fore femur with 3 long, black spine-like posteroventral setae on basal half ( Figs 30, 36); wing often with discal crossband ( Figs 31, 37) .................................................................................................. 5

4. Male and female postpedicel with base narrowly yellow ( Fig. 4); wing with infuscation around R 2+3 distal to cell dm ( Fig. 7); lateral margin of scutum paler than medially ............................................. ................................................................................................................... A. albibarba ( Loew, 1869)

– Male postpedicel entirely yellow ( Figs 21, 23); female postpedicel with base narrowly yellow; wing without infuscation around R 2+3 distally ( Figs 22–23); scutum not paler laterally ............................. ......................................................................................................... A. nigrimana ( Zetterstedt, 1846)

5. Wing without discal crossband; fore tibia with long, strong posteroventral seta on apical third, length twice width of tibia [male unknown] ................................................................ Acanthocnema sp. A

– Wing with discal crossband ( Figs 31, 37); fore tibia without long, strong posteroventral seta on apical third ( Figs 30, 36) ............................................................................................................................. 6

6. Fore femur with 3 long spine-like posteroventral setae, without distal row of strong posteroventral setae ( Fig. 30); crossvein dm-m oblique, aligned with apex of M 4 ( Fig. 31) A. pulchripennis sp. nov.

– Fore femur with four long spine-like posteroventral setae and distal row of strong posteroventral setae ( Fig. 36); crossvein dm-m not aligned with apex of M 4 ( Fig. 37) ........ A. rainierensis sp. nov.

7. Male palpus yellow ( Fig. 13), dark in female; male sternite 5 divided into pair of divergent lobes ( Fig. 18); fore tibia usually with 1 posteroventral seta near mid-length, 1 preapical posteroventral seta, slender, as long as basal width of fore femur and row of short, strong, black anteroventral setae proximal to ventral spur ............................................................................. A. capillata ( Loew, 1872)

– Palpus pale to dark brown in both sexes ( Figs 49–50); male sternite 5 not divided into pair of divergent lobes ( Fig. 52); fore tibia with 0–1 posteroventral setae near mid-length, similar to ventral spur, without row of short, black anteroventral setae .................................... A. torrenticola sp. nov.