Mandible-dimorphism
Guides
Omus audouini
Audouin's Night-stalking Tiger Beetle
Omus audouini, commonly known as Audouin's Night-stalking Tiger Beetle, is a nocturnal tiger beetle species in the family Cicindelidae. It exhibits pronounced sexual size dimorphism with females larger than males, and possesses mandibles that serve dual functions for prey capture and mating amplexus. The species shows niche partitioning with sympatric O. dejeanii through body size and mandible length differences following Hutchinsonian Ratios. It is of conservation concern in Canada due to its extremely limited distribution.
Omus dejeanii
Greater Night-stalking Tiger Beetle
Omus dejeanii is a flightless tiger beetle and the largest species in its genus, measuring 15–20 mm. It inhabits dense coastal forests from British Columbia to northern California. The species is nocturnal and exhibits exceptionally long mating durations averaging 29.4 hours, far exceeding most other tiger beetles. Males possess enlarged mandibles used both for prey capture and for grasping females during prolonged amplexus.