The identity of Canthydrus testaceus (Boheman, 1858) and a new faunistic record of Sternocanthus indicus (Wehncke, 1876) (Coleoptera: Noteridae)

During the recent revision of the Asian species of the genus Canthydrus Sharp, 1882 (Toledo & Negri 2024) it was not possible to ascertain the identity of Hydrocanthus testaceus Boheman, 1858 described from “China”, because the insect collection of the Swedish Museum of Natural History in Stockholm, where the type material of this taxon is housed, was temporarily inaccessible. Accessibility to the collections has now been restored, and the examination of what is presumably the only available syntype of Hydrocanthus testaceus reveals that it is a female of a small, uniformly pale Canthydrus. To ensure taxonomic stability, the syntype is here designated as the lectotype of Hydrocanthus testaceus Boheman, 1858. Although no male genitals are available for a more precise diagnosis, the external morphology clearly shows that it belongs to the species currently named Canthydrus ritsemae (Régimbart, 1880), which has already been recorded for southern China (Toledo & Negri 2024). The synonymy of these two species-names was already hypothesized by Toledo (2003). According to the ICZN (1999: Article 23), the species-name testaceus Boheman, 1858 has priority over ritsemae Régimbart, 1880. Therefore, Hydrocanthus ritsemae Régimbart, 1880 syn. nov. becomes a junior subjective synonym of Hydrocanthus testaceus Boheman, 1858. Consequently, Canthydrus javanus Wehncke, 1883 and C. pseudoflavus Rocchi, 1986, so far junior synonyms of C. ritsemae, now also become synonyms of C. testaceus. For full bibliography of all concerned species, see Nilsson (2011) and Toledo & Negri (2024).