Guide To The Aquatic Heteroptera Of Singapore And Peninsular Malaysia: Vii. Family Helotrephidae Author Zettel, Herbert Author ek, Miroslav Papá Author Kovac, Damir text Raffles Bulletin of Zoology 2011 2011-08-31 59 2 171 179 journal article 10.5281/zenodo.10107176 2345-7600 10107176 Key to the species of Helotrephes 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