Hydronomus Schoenherr, 1825

ROBERTO CALDARA, CHARLES W. O’BRIEN & MASSIMO MEREGALLI, 2017, A phylogenetic analysis of the aquatic weevil tribe Bagoini (Coleoptera: Curculionidae) based on morphological characters of adults, Zootaxa 4287 (1), pp. 1-63 : 33

Genus Hydronomus Schoenherr, 1825 resurrected name

Hydronomus Schoenherr, 1825 : c.583 (type species: Curculio alismatis Marsham, 1802 ). Tournier 1874: 103. Schilsky 1907: D. Sharp 1917a: 31. Solari 1930: 46. Hustache 1930: 236. Klima 1934: 127. Hoffmann 1954: 711, 713. Dieckmann 1983: 351, 373. Caldara & O'Brien 1998: 137. Alonso-Zarazaga & Lyal 1999: 88. Caldara 2013: 172.

Diagnosis. Scales subgranulate to granulate, moderately pitted except for ventrites 3–5 (char. 2.1). Rostrum with very few lateral and dorsal apical setae (char. 11.0). Scrobe not reaching eye (char. 17.1) and squamose (char. 14.1). Forehead between eyes not sulcate nor foveate (char. 24.0). Postocular lobe ventrally indistinct, not raised, not forming discontinuity with anterior prosternal margin (char. 30.0). Prosternal canal absent (char. 31.0). Elytra lacking declivital calli (char. 36.0). Tibiae arcuate at apical outer margin (char. 48.1); inner margin of tibiae lacking denticles. Penis with long apodemes (char. 110.0). Endophallus with basal sclerite complex formed by overlapped plates (char. 90.3).

Remarks. In the all-species analysis the genus is sister to all the other Bagoini with a strong support in BI (91% pp), and a lower support in ML and MP (respectively, 76% bs and 57% sr). In the type-species analysis the genus was not supported as sister to the remaining taxa of the tribe (BI: 50% pp, ML and MP lower than 50%). This incongruence was probably determined by the fact that Hydronomus is monotypic, whereas the other genera have a large number of species, sharing the character states differentiating them from Hydronomus . In the all-species analysis this resulted in a much stronger support for the clade encompassing the other genera of the tribe. Hydronomus shares with the other Bagoini several characters, such as the pitted scales, shape of the body, legs, and male and female genitalia. It differs from them by the absence of a prosternal canal and of pitted scales on some ventrites. Four unequivocal character states characterize Hydronomus (char. 11.0, 14.1, 17.1, 90.3) in respect to the other Bagoini: scrobe not reaching eyes and squamose (an apparently plesiomorphic state), rostrum with very few lateral and dorsal apical setae, endophallus with basal sclerite complex formed by overlapped plates.

This genus is presently composed only of the type species. However, we have an undescribed Chinese taxon belonging to this genus and differing from H. alismatis by the shape of the body of the penis and the basal sclerites.

Species included. PAL: * Hydronomus alismatis (Marsham, 1802) .