Key to species of Ptilocerembia (adult males)

1. Median area of inner side of 10 RP with a microspiculate promontory near a projecting hook; LC1 short, distally large echinulate nodule expanded and lobed; LC2 shorter, subconical, fused to LC1; 10LP gradually arched leftward, evenly tapering to apex; MF with a sharp hook................................... Ptilocerembia catherinae sp. n.

- Media area of inner side of 10 RP without a microspiculate promontory near a projecting hook........................ 2

2. LC1 subcylindrical....................................................................................... 3

- LC1 clavate.............................................................................................. 4

3. LC1 basally subcylindrical, distally expanded and lobed; LC2 long, subconical; 10LP broad, medially constricted then distally expanded; MF with a short sharp hook.............................................................. P. roepkei

- LC1 excavated on inner side of basal half, dilated terminally; LC2 short, subconical; 10LP medially slightly expanded, terminally subacute; MF with a dorsal hook curving forward.......................................... P. thaidina sp. n.

4. MF with a long sickle-shaped hook, elevated nodule; 10LP slender constricted basally then tapered distally; Basal portion of left cercus tubular, elongated, half t h e length of the cercus, its echinulate lobe rather small, its caudal width gradually constricting to equal that of atrophied base of LC2.......................................... P. ro s s i sp. n.

- MF with a short sickle-shaped hook, elevated nodule; 10LP slender, apex abruptly pointed; basal portion of left cercus subcylindral, gradually lobed distally, entire inner face coarsely echinulated; LC2 shorter, subconical.............................................................................................................. P. senathami sp. n.