Cyanide-tolerance
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.
Phengodidae
glowworm beetles, glow-worms, railroad-worms, trenecitos, bigotudos
Phengodidae is a family of bioluminescent beetles commonly known as glowworm beetles. The family contains over 250 described species distributed throughout the New World from southern Canada to Chile, with additional diversity in Western Asia through the subfamily Cydistinae. Females and larvae possess bioluminescent organs that emit yellow, green, or red light; the Brazilian railroad worm Phrixothrix hirtus is the only terrestrial organism known to produce true red light. Females are larviform and typically much larger than males, which are winged, short-lived, and often attracted to lights. The family was formerly considered to include the Old World Rhagophthalmidae, now recognized as a separate family.
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.
Promecognathus crassus
Straight-jawed Pedunculate Ground Beetle
Promecognathus crassus is a specialist predatory ground beetle endemic to the Pacific coast of North America. It exhibits exceptional physiological tolerance to hydrogen cyanide and benzaldehyde, enabling it to prey on cyanogenic millipedes that are chemically defended against most predators. The species has been documented to withstand cyanide exposures 7–15 times greater than doses that incapacitate other carabid beetles, with individuals remaining active after two hours of high-concentration exposure. This tolerance appears to be a specific adaptation supporting its obligate millipede diet, as the beetles do not employ behavioral avoidance of their prey's chemical defenses.
Promecognissimus laevissimus
smooth millipede hunter
Promecognathus laevissimus is a ground beetle specializing in predation on cyanide-producing millipedes. It possesses exceptional physiological tolerance to hydrogen cyanide and benzaldehyde, toxins that incapacitate most other predators. The species exhibits unique prey-handling behaviors and has been extensively studied for its biochemical resistance mechanisms, which may have potential applications in human medicine for cyanide poisoning treatment.