Hydraena Kugelann, 1794

PERKINS, PHILIP D., 2007, A revision of the Australian species of the water beetle genus Hydraena Kugelann (Coleoptera: Hydraenidae), Zootaxa 1489 (1), pp. 1-207 : 12

Hydraena Kugelann, 1794

Hydraena Kugelann, 1794: 578 (type species Hydraena riparia Kugelann 1794: 579 ; by monotypy).

The speciose, cosmopolitan genus Hydraena is well defined by the following autapomorphic characteristics: 1) presence of a labral-mandibular interlocking device ( Perkins 1989), 2) mentum with an acute median projection anteriorly ( Perkins 1989), 3) various complex sensilla ( Perkins 1997), and 4) specialized features of the exocrine secretion delivery system ( Perkins 1997). There is general agreement among current workers that Hydraena is monophyletic, based on these characters (for example, Jäch et al. 2000). The Australian species meet these generic criteria.

The division of Hydraena into subgenera is currently a matter of uncertainty. Some groupings of species into large putative monophyletic groups is more certain, but the sister group relationships of these groups are less clear, and presently under study (Ignacio Ribera and colleagues, for example, are currently doing DNA analysis). The morphological cladistic analysis of Jäch et al. (2000) concluded that "the great phylogenetic alternative" to Hydraena (s. str.) had been found in Hydraena (Hydraenopsis) . The Australian species of Hydraena , with the possible exception of H. affirmata , are most probably related to species placed by Jäch et al. in Hydraena (Hydraenopsis) . However, I prefer not to formally assign species to subgenera until the results of a comprehensive DNA analysis are published, and it is shown that Hydraenopsis is not nested within what is now considered Hydraena (s. str.).