Genus Megalotomus Fieber, 1860

Megalotomus Fieber, 1860: 58 . Type species by subsequent designation (Oshanin, 1912: 24): Alydus limbatus Herrich-Schaeffer, 1835 (= Cimex junceus Scopoli, 1763). Ghauri, 1972: 285–287; Hsiao, 1977: 276–277; Nonnaizab, et al., 1986: 305–313; Moulet, 1995: 272–273; Liu & Liu, 1998: 41–43; Dolling, 2006: 38.

Huphus Mulsant & Rey, 1870: 157–158 (Synonymized by Puton, 1872: 311). Type species by subsequent designation (Kerzhner, 2003: 103): Alydus sareptanus Baerensprung, 1859 (= Alydus ornaticeps Stål, 1858).

Diagnosis. Megalotomus differs from other genera of the family Alydidae by the combination of the following characters: body slender, small to large sized, body length range 10.0–17.0 mm, body colour from yellow to black; head almost triangular, slightly narrower than pronotum; antennal segment I longer than or equal length to segment II; posterior angles of pronotum prominent, slightly raised, always pointed; femur and tibiae straight with no curving, tibiae longer than femur, femora with 3–8 spines, inner surface with plectrum; genital capsule with a pair of surcapsular spines, never crossing over, parameres elongate, slender and curved; posterior margin of female abdominal sternite VII split longitudinally in middle [valid only if specimens of female Megalotomus quinquespinosus (Say, 1825) are examined and confirmed].

Distribution and diversity. This genus is distributed in the Palaearctic and Nearctic Regions, and according to the literature (Dolling 2006) and the results presented herein contains eight species: Megalotomus junceus (Scopoli, 1763); Megalotomus quinquespinosus (Say, 1825); Megalotomus ornaticeps (Stål, 1858); Megalotomus costalis Stål, 1873; Megalotomus castaneus Reuter, 1888; Megalotomus angulus (Hsiao, 1965); Megalotomus zaitzevi Kerzhner, 1972; Megalotomus acutulus Liu & Liu, 1998 . Among these, seven species occur in the Palaearctic Region, with only M. quinquespinosus (Say, 1825) recorded from the Nearctic Region. A new combination transferred from Alydus to Megalotomus and a new junior synonym are proposed below.