Hydraena (Hydraenopsis) dilutipes

Perkins, Philip D., 2017, Hydraenidae of Madagascar (Insecta: Coleoptera), Zootaxa 4342 (1), pp. 1-264: 109

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Hydraena (Hydraenopsis) dilutipes


Hydraena (Hydraenopsis) dilutipes  species group

Seven species are included in this group: H. dilutipes  , H. dilutipoides  , H. pilotumida  , H pilobova  , H. divisa  , H. longiloba  , and H. renalisa  .

Members of this group are moderately large to large (ca. 1.53–2.10 mm), dark brown, with coarse and dense dorsal punctation. Males have distinctive metatibial brushes. The plaques vary in size and position according to the species.

The aedeagi have a similar general plan: the distal piece is very elongate and lobate, at the base of which is a complex multilobed structure that bears the gonopore; the basal orifice has a characteristic shape and orientation. All species have a large right paramere, but there is variation in the size of the left paramere, which is sometimes absent (only a pore in that location). In the holotype of H. dilutipes  the left paramere is long, but exceedingly thin and appears to be flexible and slightly twisted ( Fig. 100); in other specimens of this species it appears that the paramere has been broken, and only the basal "stub" is present ( Fig. 101View FIGURES 101 – 102). Males in the group have thick musculature surrounding the aedeagus, and it is likely that a very thin and fragile paramere, with an especially weak point near the base, could be broken during dissection. In two other species of this group the remnant of the left paramere tapers to a very fine point, perhaps indicating that it has not been broken during dissection (e.g., Fig. 102View FIGURES 101 – 102). H. renalisa  has a long left paramere, whereas H. dilutipoides  and H. longiloba  have a very short, sharply pointed "paramere", and in H. divisa  , H. pilotumida  , and H. pilobova  only a pore appears to be present in the appropriate location.

Even though some of these species have only one functional paramere (the right), they are placed in the subgenus Hydraenopsis  because of the following characters: 1) the genae do not have a posterior ridge; 2) the metaventrite does not have an anteromedian carina; and 3) the mesotibiae of males do not have prominent spines on the medial margin.