Key to species of Acnephalomyia

The following key is useful only for male specimens, and, because it makes use of male genital characters, it may be necessary to excise and macerate terminalia. If this is impractical, identifications may be achieved by comparing visible structures of the hypandrium with illustrations provided in this paper.

1 Small flies with wing length (from humeral crossvein to tip) less than 3.5 mm; ♂ genitalia as in Figs 41–43 ........................................................................ iota sp. n.

– Bigger flies with wings greater than 4 mm in length.............................................2

2 Hypandrium (Figs 24, 25) in ventral view more or less triangular in shape, and not markedly constricted at midlength; medial lobe broadly rounded........................... ............................................................................ andrenoides (Wiedemann, 1828)

– Hypandrium in ventral view not triangular in shape, markedly constricted at or before midlength; medial lobe finger­like with narrowly rounded or slightly clavate tip...........................................................................................................................3

3 Distal ends of inner lobes of gonocoxites (Figs 45, 46) broadly expanded in dorsal view.................................................................................................. leukoros sp. n.

– Distal ends of inner lobes of gonocoxites narrow with moderately rounded distal end in dorsal view..................................................................................................4

4 Epandrium well-developed, about as long as broad; distal end of outer lobe of gonocoxite fairly broad and somewhat truncate (Figs 38–40) .......... eremia sp. n.

– Epandrium reduced, shorter than broad; distal tip of outer lobe of gonocoxite fairly acutely pointed .......................................................................................................5

5 Hypandrium very long, with greatest length:greatest breadth ratio>1.5; base of hypandrium with dorsal plate­like flange dorsally (Figs 50, 51) ............................. ......................................................................................................... probolos sp. n.

– Hypandrium long, but greatest length:greatest breadth ratio <1.5; base of hypandrium without dorsal plate­like flange dorsally .....................................................6

6 Scape and pedicel usually yellowish, contrasting with dark red-brown postpedicel; male abdomen with fine silky white setae laterally; hypandrium suddenly becoming constricted at about midlength (Figs 36, 37)................. dorsalis (Macquart, 1838)

– Antennae uniformly dark red-brown postpedicel; male abdomen with course white recumbent setae laterally; hypandrium gradually becoming constricted at about midlength (Figs 48, 49)................................................. platygaster (Loew, 1858)