Promecognathinae
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Promecognathus
Promecognathus is a genus of ground beetles comprising two described species, P. laevissimus and P. crassus. These beetles are specialist predators of cyanide-producing flat-backed millipedes in the family Xystodesmidae. They possess exceptional physiological tolerance to hydrogen cyanide, surviving doses 7–15 times greater than those lethal to other carabid beetles. This tolerance allows them to attack millipedes directly without behavioral avoidance of chemical defenses, representing the first documented case of cyanide tolerance in predatory insects.