S. Mahunka szerk.: Folia Entomologica Hungarica 57. (Budapest, 1996)

mann, 1919) (type species: Dytiscus elegáns Panzer, 1794, fixed by Guignot, 1941, by subsequent designation). The genus Scarodytes Des Gozis, 1914 originally included three species (Dytiscus halensis Fabricius, 1787; D. lineatus Fabricius, 1775 and Hydroporus meridionalis Aubé, 1838). Most writers have used this generic name for Dytiscus halensis, implying that this is the species that the genus is based on. J. Balfour-Browne (1944) was the first who designated Dytiscus lineatus as the type. His action is valid and acceptable in every respect. Nevertheless, Guignot (1946) and Nilsson et al. (1989) have accepted Dytiscus halensis as the type, and Zimmermann's (1933) statement ("Errichtung eines eigenen subgenus") as the fixation of the type. As this statement is not accepted here as an unambiguous designation of the type, therefore, a new generic name is established for Dytiscus halensis (see below). The objective synonymy of the names Scarodytes and Porhydrus Guignot, 1945 makes it necessary to suppress Porhydrus, which is younger. Rhiacodytes gen. n. Type species: Dytiscus halensis Fabricius, 1787 (present designation) — Body elongate-oval, somewhat flattened dorsally. Colouring yellowish; head and pronotum with dark marks; elytra with a dark colour pattern fasciate, variegate, fairly well delimited. Clypeus truncate, barely emarginate and not bordered anteriorly. Eyes well developed. Last segment of labial palpi truncate apically, barely emarginate at tip. Pronotum without either submarginal or latero-basal stria. Lateral border of pronotum distinct. Pronoto-elytral angle insignificant. Scutellum hidden. Elytra without impressed discal striae and without distinct preapical indentation. Elytral punctuation fine and dense; surface with more or less distinct pubescence. Elytral margin (in lateral view) barely arched at shoulder. Epipleura broad at base, abruptly narrowed at the middle, hence narrow to apex, without a distinct basal cavity and without a diagonal carina crossing near base. Ventral side simply punctuated; surface, in a major part, smooth and glossy, vaguely reticulated near sides. Metacoxal processes distinctly separated from each other at apex by an angular median emargination. Pro- and mesotarsi pseudotetramerous, with segment IV smaller than III, and even locked (concealed) between apical lobes of segment III, so that segment V appears to be the IV. Posterior (apical) margin of first four segments of metatarsi transversely straight, without natatory hairs. There is a great confusion about the type designation of the genus Hydroporus Clairville, 1806. This genus originally included the following seven species: Dytiscus bicarinatus Latreille, 1804; Hydroporus fuscatus Clairville, 1806 (a nomen nudum); Dytiscus fusculus Schrank, 1781, D. gibbus Fabricius, 1776; D. ovalis Thunberg, 1784; D. parvulus Fabricius, 1792 (a doubtfully included species) and D. sexpustulatus Fabricius, 1776. Dytiscus depressus Fabricius, 1775 was designated as the type by Curtis (1831); D. duodecimpustulatus Fabricius, 1792 by Westwood (1838); D. palustris Linnaeus, 1761 by Thomson (1859); D. parvulus Fabricius, 1792 by Crotch (1870); Hyphydrus pubescens Gyllenhal, 1808 by Guignot (1946) and Dytiscus erytrocephalus Linnaeus, 1758 by Zaitzev (1953). Only one nominal species of these, Dytiscus parvulus was originally included in Hydroporus. However, this is excluded from the consideration in determining the type, therefore, just as the other type fixations, Crotch's designation is also invalid.