Hydraena (Monomadraena) impressicollis

Perkins, Philip D., 2017, Hydraenidae of Madagascar (Insecta: Coleoptera), Zootaxa 4342 (1), pp. 1-264 : 38

Hydraena (Monomadraena) impressicollis species group

Four species are included in this group: H. impressicollis , H. furcula , H. bergsteni , and H. oscillata . The dorsal habitus is similar to that of the H. dilutipes group; however, members of that group do not have an anteromedian carina of the metaventrite, a structure that is present and strong in members of the H. impressicollis group. The anteromedian carina joins the anterior extremes of the plaques, together forming an inverted Y-shape. The genae are raised, rugulose or shining, and have a distinct posterior ridge, interrupted in the midline. The mesotibiae of males have prominent sharp spines, usually 5–6, on the medial margin, with the margin notched between the spines. The metatibiae of males may be slightly arcuate, but do not have prominent brushes of setae, which are present in members of the H. dilutipes group.

The aedeagi (e.g., Figs. 31–32 ) are unusual in the position and shape of the single (right) paramere: the paramere originates distally on the main piece, not near the basal orifice, and is short and lobate, therefore differing markedly from that of members of the H. dilutipes group. Likewise, the aedeagus is very dissimilar to the aedeagi of members of the H. epipleurata group, which are usually very broad species that have the metaventrite with an anteromedian carina. The four species in this group appear to be isolated from the other groups.

Figures

FIGURES 31 – 32. Hydraena, aedeagi of H. impressicollis (lectotype) and H. bergsteni (holotype).