Key to males of the Microphorella acroptera species group

1 Wing with vein CuA+CuP modified as a spot (Fig. 89); face and clypeus silvery (Fig. 87), face narrow at middle, clypeus projecting to lower eye level with rounded ventral margin; antennal postpedicel with elongate narrow apex (Fig. 87); lower postocular setae and coxal setae white (Figs 87, 86).......................................... M. maculata sp. nov.

- Wing without spot-like CuA+CuP vein (Fig. 95); face and clypeus brown or blackish, clypeus not projecting to lower eye level with truncate ventral margin; antennal postpedicel without elongate narrow apex (e.g., Figs 4, 6, 58, 72); body with all setae dark (e.g., Figs 64–66, 92).............................................................................. 2

2 Abdominal sternite 6 with narrow projecting process (Fig. 96); hind trochanter with tubercle large and rounded or disc-shaped (Figs 93, 94); hypandrium with knob-like or dome-like posterior protrusion (Figs 97, 98); cercus digitiform and curved medially, with long setae (Fig. 99)................................................................................ 3

- Abdominal sternite 6 without narrow process; hind trochanter with tubercle cylindrical, clavate or rounded (Figs 8, 9, 18, 21, 66); hypandrium without posterior protrusion (e.g., Figs 11, 12, 29, 30, 67, 68, 78–80); cerci not as above (e.g., Figs 31, 38, 43, 55, 69, 82)........................................................................................... 4

3 Hind tibia with dorsal row of about 5 long setae, shortening distally (Figs 92, 93); abdominal sternite 8 with greatly elongated setae on posterior margin (Figs 92, 96); hypandrium with narrow knob-like posterior protrusion (Figs 97, 98)............................................................................................ M. trochanterata sp. nov.

- Hind tibia without row of long setae; abdominal sternite 8 with setae on posterior margin not greatly elongated; hypandrium longer with broad dome-like posterior protrusion............................................ Microphorella sp. A

4 Antennal postpedicel long and triangular, longer than stylus (Fig. 58); hind basitarsus with short, spur-like basiventral seta (Fig. 59)............................................................................... M. triangulata sp. nov.

- Antennal postpedicel bulb-shaped, usually distinctly shorter than stylus (e.g., Figs 4, 34, 56, 65, 71, 72); hind basitarsus with or without spur-like basiventral seta....................................................................... 5

5 Halter pale yellow (Figs 23, 32, 34, 35); hind basitarsus without spur-like basiventral seta............................ 6

- Halter brown to blackish (e.g., Figs 4, 6, 56, 63, 72); hind basitarsus with or without spur-like basiventral seta............ 7

6 Hypopygium large compared to rest of abdomen (Figs 34, 35); hypandrium large and ovoid with anterior end broadly rounded (Figs 41, 42); phallus slightly inflated in middle portion, with U-shaped curve protruding posteriorly (Figs 41, 42, 44, 45)..................................................................................... M. serpentina sp. nov.

- Hypopygium smaller (Figs 32, 33); hypandrium with anterior end tapered and broadly conical (Figs 36, 37); phallus greatly inflated in middle portion (Figs 39, 40), without protruding U-shaped curve (Figs 36, 37)......... M. paracroptera sp. nov.

7 Hind trochanter with large clavate tubercle bearing blunt-tipped spine-like seta (Fig. 66); hypopygium distinctive (Figs 61, 66) with projecting posterior components prominent and pale yellow (i.e., surstyli, postgonites, phallus); cercus large with pale yellow base and dark subtriangular apical lobe (Figs 60, 61, 66–69); face narrowing below to width of anterior ocellus, dark coppery brown (Fig. 63)............................................................... M. tubifera Melander

- Hind trochanter with tubercle smaller, shorter and usually cylindrical (Figs 8, 9, 21, 24, 48, 51, 73, 77, although sometimes clavate in M. bifida sp. nov., Fig. 18); hypopygium with cercus and most other projecting posterior components brownish; cercus structure and colouration not as above; face broader than width of anterior ocellus............................ 8

8 Hind basitarsus with very small, stout, basiventral spur-like seta (Figs 22, 57)..................................... 9

- Hind basitarsus without basiventral spur-like seta........................................................... 10

9 Hind trochanter tubercle rounded, globular with small spine-like seta (Fig. 21); cercus with narrow, dorsally-projecting lobe (Figs 29–31); dorsal lobe of surstylus with 3–4 prensisetae (Figs 29, 30) on right and left sides of hypopygium; apical portion of phallus (distal to inflated part) elongate, with U-shaped curve protruding posteriorly (Figs 29, 30).. M. convoluta sp. nov.

- Hind trochanter tubercle cylindrical with large spine-like seta (as in Fig. 8); cercus without narrow, dorsally-projecting lobe (similar to Figs 11, 12); dorsal lobe of surstylus with 1 well-developed prensiseta on right side only (Fig. 16); apical portion of phallus (distal to inflated part) shorter, without protruding U-shaped curve (as in Figs 11–15)...... M. subacroptera sp. nov.

10 Thorax with acrostichal setae sparse and irregular, or absent; ventral epandrial process with hook-like tip (Fig. 11); right dorsal surstylar lobe thumb-like, bearing blade-like prensiseta laterally (Fig. 12)....................... M. acroptera Melander

- Thorax with acrostichal setae well-developed and biserial; ventral epandrial process with variable tip (Figs 25, 51, 52, 54, 78, 79, 81, 84, 85); right dorsal surstylar lobe broad and truncate, bearing 2 prominent prensisetae (Figs 26, 53), or short and broad, bearing 4 setae (Figs 80, 83)............................................................................ 11

11 Thorax dull, dark bronze pruinose in dorsal view; hypopygium large with prominent, bulbous hypandrium (Figs 18, 25, 26, 51–53); cercus elongate (Figs 28, 55); left dorsal surstylus short and broad (Figs 25, 52)............................ 12

- Thorax blackish with blue tinge in dorsal view; hypopygium more compact with smaller, narrower hypandrium (Figs 74–81, 83, 85); cercus small and short (Figs 78–85); left dorsal surstylus elongate and narrow (Figs 78, 79, 81, 84, 85).......... 13

12 Cercus with bifid lateral lobe (Fig. 28)....................................................... M. bifida sp. nov.

- Cercus with undivided, digitiform lateral lobe (Fig. 55)........................................ M. sinuosa sp. nov.

13 Phallus greatly elongated and C-shaped with broadened apex (Figs 83, 84)........................ M. elongata sp. nov.

- Phallus shorter and J-shaped with narrow apex (Figs 78, 79, 81, 85)............................................ 14

14 Ventral epandrial process gradually tapered apically to narrow pointed tip (Fig. 78); left postgonite with long, thick apical projection (Fig. 78); phallus well-sclerotized with long ventral process arising basally and extending to full length of phallus (Fig. 78)........................................................................... M. acuminata sp. nov.

- Ventral epandrial process not gradually tapered apically (Figs 79, 81, 85); left postgonite with apical projection short and narrow, or long and narrow (Figs 79, 81, 85); phallus robust or delicately sclerotized, with process shorter and arising near middle or preapically (Figs 79, 81, 85)................................................................... 15

15 Left postgonite with short apical projection (Fig. 85); phallus with short, narrow, pointed process arising preapically and extending nearly to tip of phallus (Fig. 85)................................................... M. tenuis sp. nov.

- Left postgonite with long apical projection (Figs 79, 81); phallus robust with short, thick process arising near mid-length that ends well before tip (Fig. 79), or thin and delicately sclerotized, with narrow pointed process extending nearly to phallic tip (Fig. 81)........................................................................................... 16

16 Phallus thin and delicately sclerotized, with narrow pointed process arising preapically and extending nearly to phallic tip (Fig. 81); tip of ventral epandrial process with digitiform dorsoapical process (Fig. 81); right postgonite not protruding below ventral lobe of surstylus and even with posterior epandrial margin..................................... M. compacta sp. nov.

- Phallus robust with short, thick process arising near mid-length that ends well before tip (Fig. 79); tip of ventral epandrial process emarginate, without digitiform dorsoapical process (Fig. 79); right postgonite protruding below ventral lobe of surstylus and extending beyond posterior epandrial margin (Fig. 80)..................................... M. cornuta sp. nov.