Acomoptera Vockeroth

Kerr, Peter H., 2011, Six new species of Acomoptera from North America (Diptera, Mycetophilidae), ZooKeys 137, pp. 41-76 : 42-44

Acomoptera Vockeroth

Acomoptera Vockeroth, 1980: 534

Type species.

Eudicrana plexipus Garrett, 1925: 4, by subsequent designation.

Diagnosis.

This genus may be distinguished from most mycetophilid genera by the following combination of wing characters: Sc ending in C, sc-r present near middle of Sc, and R4 present and displaced from Rs by more than 2.5 × its own length. Acomoptera may be distinguished from Paratinia by having wing membrane bare and from Drepanocercus by having the cubital fork near the level or distad of sc-r. Acomoptera is distinguished from Phoenikiella Chandler by having a setose Sc, with sc-r positioned near the middle of this vein.

Description.

Body length 4.5 to 7.1 mm. Ocelli three, subequal or median ocellus reduced, lateral ocellus separated from eye margin by approximately its own diameter or clearly less. Eye with a broad distinct emargination above antennal base, with microsetae usually scattered and short, but sometimes more numerous and longer. Frons bare between ocelli and antennal bases. Frontal tubercle present. Antenna two to four times as long as thorax, 2/3rds to approximately same length as abdomen; antennal bases nearly touching, separated only by narrow tip of frontal tubercle; all flagellomeres densely setulose, elongate, flagellomere length decreases gradually toward tip. Palpus with five palpomeres; palpomere 1 short, as wide as long, remaining palpomeres longer than wide (except sometimes palpomere 2 as wide as long); palpomere 2 clearly shorter than or subequal to palpomere 3; palpomere 4 three to six times longer than wide; palpomere 5 thinner than others, six to eleven times longer than wide, usually subequal to combined length of palpomeres 3 and 4. Scutum with short appressed acrostichal and dorsocentral setae and longer and more erect sublateral setae, the intervening areas bare. Scutellum with three or four irregular rows of short to long setae, sometimes bare medially. Paratergite present; antepronotum with setae on posterior half, proepisternum bare; mesopleuron, metapleuron, and prosternum bare; metanotum with one to three erect setae laterad of base of halter; mediotergite and laterotergite bare; phragma not well developed. Wing unmarked, with dense microtrichia, without macrotrichia. Costal vein extends beyond R5, between approx. 0.25 × and 0.33 × distance between R5 and M1; sc-r crossvein present, slightly distad of middle of Sc, proximal of Rs; R4 present (when missing, teratogenic), located approx. 3 × its own length from Rs, forming an elongate radial cell; medial fork approx. 3 × longer than stem; cubital fork arises near level or distad of sc-r and proximad of medial fork, cubital stem shorter than CuA1 and approx. equal in length to or longer than CuA2; all cross veins bare on upper surface, all longitudinal veins setose on upper surface, except CuP and the first two sections of M bare (as an exception, Acomoptera crispa sp. n. may have a few setae on M1+2); wing veins R1, R5, M1, and sometimes M2 with at least some setae on lower surface. Hind coxa with a single vertical row of setae on at least proximal half (sometimes weak). Tibial bristles short but distinct, the longest between half and full tibial diameter in length. Anteroapical depressed area of fore tibia ovate and well developed. Tibial spur pairs of equal length, hind tibial spurs usually longer than mid tibial spurs, but sometimes mid and hind spurs subequal in length. Tarsal claws each with one or two small ventral teeth. Empodia small. Sternite 1 bare. Sternites 2 to 7 each with a pair of broad, poorly defined, submedian to sub lateral fold-lines. Terminalia not rotated. Epandrium (tergite 9) between three times as wide as long to slightly wider than long. Hypandrium (sternite 9) fused with gonocoxites, the synsclerite with or without a narrow transverse membranous area across ventral surface, with or without a ventral preapical hook-like process directed posteriorly. Gonostylus variously formed, often divided into two or three lobes. Posterodorsal process attached to the median dorsal angles of the gonocoxites variously shaped, sometimes arising as a distinctive bilobed wing-like structure whose posterior margins are darkened and toothed. Cerci broad, flat, broadly rounded apically, with fine setae. Hypoproct broad, semicircular, weakened anteromedially.

Female sternite 8 deeply emarginate posteriorly, the rest of the median area membranous or lightly sclerotized. Sternite 9 with two weakly sclerotized anterolateral areas and two slender, more heavily sclerotized submedian processes projecting posteriorly. Tergite 10 short, setose, fused on either side with sternite 10. Sternite 10 well developed, membranous medially, tapering on posterior half, posterior margin extending to apex of first segment of cercus. Cercus 2-segmented, first segment almost twice as long as wide, second segment oval.

Key to the Acomoptera of the world (males)