Unexplained-physiology
Guides
Metrius
Metrius is a genus of ground beetles (Carabidae) comprising two described species: Metrius contractus and Metrius explodens. The genus is notable for exhibiting exceptional tolerance to hydrogen cyanide, a trait shared with the millipede-specialist genus Promecognathus. Unlike Promecognathus, however, there is no documented evidence of millipede predation in Metrius, and the ecological basis for this cyanide tolerance remains unexplained.