Key to species of the Platypalpus hackmani group from North America

1 Katepisternum with large shining spot. Antenna with postpedicel about 2.5 times as long as wide..... P. arnaudi (Melander)

– Katepisternum entirely tomentose. Antenna with short postpedicel which is at most 1.5 times as long as wide........... 2

2 Dorsocentral bristles uniserial. Male: mid tibia with short, black, claw-like apical spur................ P. canus Melander

– Dorsocentral bristles at least anteriorly arranged in 2–3 (or more) irregular rows. Mid tibia without apical spur in both sexes... 3

3 Legs brown, only knees of fore pair somewhat paler........................................ P. syletor (Melander)

– Legs yellow, at most some tarsomeres brownish............................................................. 4

4 Antenna with scape and pedicel yellow, postpedicel brown. Palpus yellow. Male: right epandrial lamella cleft apically (Fig. 18)................................................................................ P. submicrophona sp. nov.

– Antenna brown. Palpus brown (except P. microphona). Male: right epandrial lamella more or less rounded apically....... 5

5 Scutum almost uniformly covered with very short setulae, acrostichals and dorsocentrals undifferentiated. Halter with pale yel- low stem and darkened knob. Male: left epandrial lamella pointed apically, with scattered, moderately long, marginal setae ventrally (Fig. 23).................................................................. P. tanbarkiensis sp. nov.

– Acrostichals separated from dorsocentrals by bare space. Halter uniformly pale yellow. Male: left epandrial lamella rounded apically, with numerous very long setae sitting fan-like on ventral tubercle (unknown in P. microphona)................ 6

6 Palpus yellow. Male unknown....................................................... P. microphona (Melander)

– Palpus brown........................................................................................ 7

7 Dorsocentrals arranged in 2–3 irregular rows. Fore tarsus yellow. Male: left epandrial lamella with finger-like projection apically (Fig. 17)....................................................................... P. layiaphilus sp. nov.

– Dorsocentrals more numerous, not arranged in regular rows and undifferentiated from supra-alar setulae. Fore tarsomeres 2–5 yellowish brown. Male: left epandrial lamella broadly rounded apically (Fig. 14).................. P. cummingi sp. nov.