Generic epithet from Greek χενός ώψ meaning "strange-faced" or "face of a stranger." Zeller explains that it is hollow-faced (inanis facies), further stating it has a "face profoundly excavated (frons profunde excavata)."
Pohl, et al. (2016) list 16 species, all included here.(1) This guide should be used only as a first step in identification; some species can't be confidently separated from photos.
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