Thirty-three new species of water beetles in the genus Hydraena Kugelann from Cameroon (Coleoptera: Hydraenidae) Author Perkins, Philip D. text Zootaxa 2022 2022-11-03 5203 1 1 66 http://dx.doi.org/10.11646/zootaxa.5203.1.1 journal article 181704 10.11646/zootaxa.5203.1.1 b6f94c7b-7033-4952-96a7-3db5fb6ad879 1175-5326 7284841 85C20298-5DF9-44DF-8485-3C64CF40CD08 Hydraena cameropetila , new species Figs. 3 , 18 (habitus), 18 (aedeagus), 43 (map) Type Material. Holotype (male): Cameroon : Northwest Province . “ BRITISH CAMEROONS . / Mamfe, 7-11.i.1949 / B. Malkin coll. // Rain forest; clear stream / Gravel and sand” ( UKNHM ) . Paratypes : Same data as holotype (2 UKNHM ) . Differential Diagnosis. Differentiated from other members of the genus in Cameroon by the combination of absence of metaventral plaques, the very narrow P2, and the aedeagus ( Fig. 18 ). For characters differentiating the two species refer to the diagnosis of H. camerosetosa . Although H. cameropetila is smaller than H. camerosetosa in body length (ca. 1.20 vs. 1.33 mm ), the width of the mesocoxae are the same in the two species, making the ratio of P2 width/mesocoxa width approximately 0.12 for H. cameropetila and 0.40 H. camerosetosa . Also refer to the diagnoses of H. millenaria and H. camerocrebrata . Description . Size: holotype (length/width, mm): body (length to elytral apices) 1.20/0.50; head width 0.30; pronotum 0.29/0.42, PA 0.32, PB 0.36; elytra 0.74/0.50. Habitus as illustrated ( Fig. 18 ). Dorsum dark brown to black, pronotum without macula, palpi brown. Dorsum of head and pronotum moderately coarsely, very densely punctulate, interstices shining; punctures of frons disc and pronotal disc ca. 2–3xef, interstices ca. 1xpd or less; punctures of clypeus moderately fine, dense. Labrum apicomedially excised, free margins rounded, weakly upturned. Pronotum with anterior margin weakly emarginate over middle 1/2; anterolateral, posterolateral and posterosubmedial foveae moderately deep, anteromedian fovea shallow. Elytra with summit of posterior declivity at about posterior 1/3; lateral explanate margins wide; on basal 1/3 punctures ca. 2xpd of largest pronotal punctures, punctures becoming gradually smaller toward posterior. Intervals not raised, width ca. 0.5xpd or less, as are interstices between punctures of a row. Apices in dorsal aspect very slightly separately rounded, in posterior aspect margins forming weak angle with one another. Venter: Mentum and postmentum densely finely punctulate, dull. Genae raised, dull, without posterior ridge. Metaventral plaques absent. P1 laminate; median carina sinuate in profile. P2 very narrow, l/w ca. 4/1, sides parallel, blunt apex raised slightly above mesoventral intercoxal process.. Metaventrite with very short longitudinal ridge on each side, extended posteriorly from margin of each mesocoxal cavity. AIS width at straight posterior margin ca. 4x P2. All tibiae slender, protibia very slightly arcuate, meso- and metatibiae straight. Abdominal apex with very small indistinct apicomedian notch. Distribution. Currently known only from the type locality ( Fig. 43 ). Etymology. Named in reference to the distribution and the very narrow mesoventral intercoxal process (P2).