D3222: An outline of genus Sphaeroderus taxonomy and an updated identification key

The Carabid snail-eating beetles of genus Sphaeroderus are endemic to eastern North America and flightless, which makes their evolutionary history complex. This paper aims to review of the taxonomy of genus Sphaeroderus and presents an updated, pictorial identification key. The study investigates the six previously accepted species within the genus, using public genetic data and an examination of both external and internal morphological characteristics. As a result of this investigation, I propose the elevation of the subspecies S. stenostomus stenostomus and S. stenostomus lecontei to full species status. Furthermore, I draw attention to a genetically distinct cluster currently named as a part of S. stenostomus lecontei and provide a summary of the current taxonomic understanding of this species complex, acknowledging the remaining unresolved aspects. In addition, I propose that S. nitidicollis nitidicollis does not warrant its subspecies designation within S. nitidicollis. This work contributes to the ongoing efforts to clarify the taxonomy of the Sphaeroderus genus.