Hygrotus Stephens, 1828

Fery, Hans, 2017, A new classification of the tribe Hygrotini Portevin, 1929 (Coleoptera: Dytiscidae: Hydroporinae), Zootaxa 4317 (3), pp. 499-529 : 518

Genus Hygrotus Stephens, 1828

Type species: Dytiscus inaequalis Fabricius, 1777: 239 , by subsequent designation of Curtis (1835: pl. 531).

The genus Hygrotus as here defined includes 129 described species (two of them bitypic) distributed in the Nearctic (including the north of MeXico), Palaearctic, Afrotropical and Oriental zoogeographical regions ( Fig. 2 and Table 1). One Nearctic species was introduced to Hawaii (see below), which belongs to the Pacific region .

Diagnosis. In the new classification Hygrotus is the second of two genera of the tribe Hygrotini . As in Clemnius n. gen. all species of the genus have two carinae in each antennal cavity (see Figs 4–6 ).

According to the two main clades in the phylogeny of Hygrotini and several morphological characters, the genus (which corresponds to Clade B in Fig. 1 ) is subdivided into four clades corresponding to the following four subgenera: clade B1 = subgenus Coelambus , clade B2 = subgenus Hyphoporus , clade B3 = subgenus Hygrotus s. str. and clade B4 = Leptolambus n. subgen.

Figures

FIGURE 1. Phylogeny of Hygrotini, modified from Villastrigo et al. (in press). Numbers above nodes are bootstrap support values. Note that here the former generic and subgeneric names are still used.

FIGURE 2. Dendrogram showing the new classification of Hygrotini. A number of species without molecular data (no voucher number) have been inserted near morphologically similar species with molecular data. Acronyms refer to biogeographical regions.

FIGURES 3 – 4. Antennal cavities of: (3) Hydroporus dorsalis (Hydroporini) and (4) Hygrotus (Leptolambus) lagari (Fery, 1992) (a: carina delimiting capsule for scape; b: fronto-lateral border of clypeus; c: second carina).

FIGURES 5 – 6. SEM micrographs with details of head and antennal cavities of: (5) Hygrotus (Leptolambus) impressopunctatus (frontal view) and (6) Hygrotus (s. str.) inaequalis (oblique ventral view) (a, b and c as in Figs 3 – 4; d: clypeal stripe; e: labrum).