Key to male Helicopsyche of Laos

1 Maxillary palp 5-segmented ............................................................................ Helicopsyche angusta Ulmer

- Maxillary palp 2-segmented ........................................................................................................................ 2

2 In genitalia, gonocoxite with long secondary branch clearly exceeding primary branch margin .............. 3

- In genitalia, gonocoxite with short secondary branch exceeding primary branch margin for a short distance, or secondary branch absent ............................................................................................................. 4

3 In genitalia, segment X with lateral processes forming a ridge on segment X, separated from segment X only at distal part; gonocoxite primary branch at most 2x broader at mid-length than proximally .............. ................................................................................................... Helicopsyche pathoumthongi, new species

- In genitalia, segment X with lateral process separated from segment X along its length; gonocoxite primary branch about 3x broader at mid-length than proximally .......... Helicopsyche antikleia Malicky, 1997

4 In forewing, fork 3 about as long as its stalk; in genitalia, segment IX nearly triangular; segment X deeply incised in dorsal view, without lateral processes, slightly curved dorsally; gonocoxite parallel-sided in lateral view ...................................................................................... Helicopsyche vongsombathi, new species

- In forewing, fork 3 nearly twice as long as its stalk; in genitalia, segment IX nearly rectangular, not incised in dorsal view, with free lateral processes, nearly straight; gonocoxite club-shaped in lateral view. .............................................................................................................. Helicopsyche laoensis, new species