Detail of right rear and middle tarsi. The tarsal claws have a little tooth, sometimes a characteristic of Cantharis, according to the Dillons (1), but that key does not include several recent splits of the genus, I believe. Arnett et al. (2) give some technical characters for Rhaxonycha in a key to genera of this family:

• mandibles simple, not toothed
• both claws of all tarsi with an elongate basal tooth, so that claws appear to be broadly cleft