Parhydraenini, Perkins, 1997

Perkins, Philip D., 2009, Revisions of the genera Parhydraena Orchymont, Protozantaena Perkins, Decarthrocerus Orchymont, and Parhydraenopsis nomen novum, aquatic and humicolous beetles from Africa and Madagascar, and comparative morphology of the tribe Parhydraenini (Coleoptera: Hydraenidae), Zootaxa 2038, pp. 1-119 : 11

Key to genera of Parhydraenini

1 Anterior extreme of wet-hypomeron enclosing part of antennal pocket; pronotum anterior margin with distinct postocular emarginations; antenna with 11 articles (six + club) ( Fig. 9); aquatic species; South Africa...................... ......................................................................................................................................................... Pneuminion Perkins

- Wet-hypomeron not enclosing antennal pocket ( Figs. 2, 3); pronotum anterior margin lacking postocular emarginations; antenna with 10 articles (five + club) ( Figs. 4–8) ............................................................................... 2

2 Hypomeral antennal pocket bordered posteriorly with sparse, indistinct, flexible setae that lie on cuticle in dry specimens ( Fig. 3); pronotum explanate, widest slightly behind middle, then markedly attenuate to posterolateral angles, each of which is produced in small acute point; explanate margin of elytron very wide (except in D. sequentia ), in habitus view concealing tibiofemoral articulation; maxillary palpi and tarsi very short ( Fig. 1); humicolous species; aedeagus with parameres very short; South Africa, Lesotho........................................................ .................................................................................................................... Discozantaena Perkins & Balfour-Browne

- Hypomeral antennal pocket bordered posteriorly, and sometimes laterally also, with long, stiff, arcuate setae (e.g., Figs. 2, 3); pronotum widest near midlength, posterolaterally subrectangulate; elytra not markedly explanate; maxillary palpi and tarsi of various lengths; aedeagus with or without parameres ..................................................... 3

3 Hypomeral carina present, separating wet- and bubble-hypomeron (e.g., Figs. 2, 88); aedeagus with large, multisetose parameres, or parameres absent (e.g., Figs. 40, 41, 86, 87)...................................................................... 4

- Hypomeron without carina, or at most with short carina in posterior only (e.g., Figs. 3, 71, 78); aedeagus with very small parameres, each with two setae, or only the two setae present, remainder of paramere lost (e.g., Figs. 69, 70, 80, 81) .......................................................................................................................................................................... 5

4 Pronotum cordate; head wide and short; elytra markedly attenuate and peaked posteriorly; dorsum with strong arcuate setae (e.g., Figs. 18, 85); antennal grooves on venter of head very wide; hypomeral antennal pocket setae originating in hydrofuge area (none along the lateral margins of the pocket), elongate, and group together at their tips (in dry specimens); aedeagus without parameres; humicolous species; Kenya, Congo, Rwanda, Tanzania................. ............................................................................................................................................ Decarthrocerus Orchymont

- Pronotum not cordate; head not markedly wide and short; elytra not markedly attenuate and not peaked posteriorly; dorsum with much shorter, less erect setae (e.g., Figs. 1, 13); antennal grooves on venter of head narrow; hypomeral antennal pocket setae in a close set row along posterior and lateral margin of antennal pocket; aedeagus with large parameres bearing setae; aquatic and humicolous species; southern Africa, Sudan, Kenya.......................................... ................................................................................................................................................. Parhydraena Orchymont

5 Size very small, ca. 1.30–1.70 mm (e.g., Fig. 1); hypomeral carina absent; hypomeral antennal pocket setae contiguous or nearly so, forming strong cup (e.g., Figs. 3, 71); aedeagus with flagelliform distal piece (e.g., Figs. 69, 73; humicolous and aquatic species; Namibia, Tanzania, and Madagascar................................ Protozantaena Perkins

- Size larger, ca. 2.12–2.38 mm (e.g., Figs. 1, 79, 82); hypomeral carina absent or only present in posterior part of hypomeron only (one species); antennal pocket setae less closely spaced; aedeagus with distal piece various, not simply flagelliform ( Fig. 80, 81,83); aquatic species; Ethiopia.................................. Parhydraenopsis nomen novum