Limnebius Leach 1815

Perkins, Philip D., 2017, Hydraenidae of Madagascar (Insecta: Coleoptera), Zootaxa 4342 (1), pp. 1-264 : 160-161

Limnebius Leach 1815 , subgenus Bilimneus Rey 1883

Previously unrecorded for Madagascar, ten new species of Limnebius are described herein. The species are, as is so common for the genus, very similar in external morphology; reliable determinations require examination of the aedeagi, in temporary slide mounts, with a compound microscope. Species vary in size from ca. 0.77 mm to 1.15 mm, and are very similar in color.

Limnebius in Madagascar have been collected in both streams and ponds. Specimens have been collected at localities from sea level up to 1470m. Some species have a wide altitudinal range; for example H nanostillus has been collected at six localities at elevations of 50, 71, 400, 545, 781, and 1470 meters. Other species appear to have a narrower range, for example L. bergsteni with a known range of 900–1100 m.

Based on the structure of the aedeagus the Malagasy species appear to be related to species from South Africa (see Perkins 2015) and Australia (Perkins 2004). The aedeagi have an internal capsule, which is located in various positions in the main piece, but always above the basal curve (i.e., not located in a basal bulb). In some Malagasy species the capsule occupies nearly the entire length of the main piece (e.g., Fig. 161) whereas in others (especially very long and slender aedeagi) the capsule is located in the distal 1/4 or 1/3 of the main piece (e.g., Fig. 156). Within the capsule, or with the tip slightly emerging subapically on the main piece, is the protrudable gonopore bearing duct; the duct varies in size among the species. The single species of Limnebius known from Australia and Papua New Guinea, L. acupunctus Perkins , also has this aedeagal type ( Perkins 2004c).

Rudoy et al. (2016) constructed a molecular phylogeny for the genus Limnebius and found that there are two main lineages: Limnebius sensu stricto and Limnebius (Bilimneus) ; consequently the subgenus Bilimneus was reerected. Their DNA sequencing included three species of interest for this study: L. endroedyi Perkins ( South Africa), L. nanostillus n. sp. (specimen " Madagascar AI549"), and L. acupunctus Perkins ( Australia, Papua New Guinea). All three of these species group within Bilimneus (Rudoy et al., 2016) . The aedeagi of all of the Malagasy species lack parameres, and the species are therefore considered members of the subgenus Bilimneus .