Helotrephes Stal 1860

1 Pronotum at hind margin without tubercles. Pronotal plate near eye with very deep, roundish incision (Fig. 42). Subgenital plate of female with broad medial lobe (Fig. 44). Apex of aedeagus narrow, hook-shaped (Fig. 48). Helotrephes australis species group.................................................... Helotrephes australis

– Pronotum at hind margin with distinct tubercles (Figs. 3, 9). Pronotal plate near eye with small incision (Figs. 43). Subgenital plate of female with narrow medial process (Figs. 45–47). Apex of aedeagus broad, not hook-shaped (Figs. 51, 54, 57). Helotrephes otoeis species group.......................................... 2

2 Cephalonotum yellowish with numerous brown speckles. Medial process of subgenital plate of female large, with weakly narrowed “neck” (Fig. 45). Aedeagus of male with broad apical lamella (Fig. 51). Southern Thailand..... [Helotrephes affinis]

– Cephalonotum almost totally bright yellow. Medial process of subgenital plate of female narrow, with distinct “neck” (Figs. 46, 47). Aedeagus of male with small, completely delimited apical plate (Figs. 54, 57)..................................................... 3

3 Subgenital plate of female moderately asymmetrical at base (Figs. 46). Aedeagus of male with wide, posteriorly sharply delimited apex (Fig. 54)...................... Helotrephes flaviceps

– Subgenital plate of female strongly asymmetrical at base (Figs. 47). Aedeagus of male with narrow, posteriorly curved apex (Fig. 57)......................................... Helotrephes rompinensis