On the authorship of Canthon rutilans cyanescens ‘Harold, 1868’ (Coleoptera, Scarabaeidae, Scarabaeinae, Deltochilini): the treatment of varieties and nomina nuda by a 19th-century zoologist

Ever since Schmidt’s (1922) review of Canthon, the authorship of the species-group name Canthon rutilans cyanescens (Coleoptera, Scarabaeidae) has been almost unanimously attributed to Harold (1868). Here, we argue that this is mistaken. This species-group name first entered the literature as a nomen nudum in Lacordaire’s 1830 memoirs of his South American beetle explorations, and there its authorship was credited to Dejean. Later, it was listed in Harold’s (1868) Canthon revision as an unavailable name referring to what he considered to be a blue variety of Canthon rutilans Castelnau, 1840. In keeping with his usual nomenclatural treatment of nomina nuda as unavailable and with his procedure of not naming infraspecific taxa, Harold did not consider ‘cyanescens Dejean’ as the valid name of that ‘blue variety’ of C. rutilans. His citation, therefore, does not make the name available by not complying with Article 11.5 of the Code. The first author to fulfil all the availability requirements of the Code was Schmidt (1922), who both treated the name as valid for a taxon and accompanied it with an indication—more specifically, an indication to Harold’s description of the blue variety of C. rutilans. It is to Schmidt (1922) that the authorship of cyanescens must, thereby, be credited. One of the specimens used by Harold to produce the description indicated by Schmidt was found by us in the Paris Museum and it is here designated as the lectotype of Canthon rutilans cyanescens.