Omus

Omus species are distinguished from other tiger beetle genera by their flightless condition, uniformly dark coloration, and nocturnal activity pattern. Adults lack functional hind wings. Larvae possess three pairs of hooks on the 5th abdominal segment (outer, middle, and inner hooks), whereas all other North American tiger beetle genera have lost the outer pair and retain only two pairs. Larval burrows are smaller than those of Amblycheila and lack the distinctive engineering modifications seen in some Cicindela species.

Forest floor habitats, upper salt marshes, and coastal areas along the west coast of North America. Omus audouini shows strong association with upper salt marsh plant communities dominated by Douglas aster (Symphyotrichum subspicatum) approximately 15 m from flood-protection dikes. Other species occupy forested areas and rain shadow zones on west slopes of the Sierra Nevada, Cascades, and Coast Ranges.

Restricted to the west coast of North America, from southwestern British Columbia, Canada, south through Washington, Oregon, and California. Species occur on the west slopes of the Sierra Nevada and Cascade ranges, the Coast Ranges, and coastal plain habitats.

Adults active primarily from May through September, with peak activity varying by species and locality. Some populations may be encountered as early as April at lower elevations. Larvae present year-round in burrows.

Larvae construct burrows in soil and are known to plug burrow entrances for extended periods. Development from 2nd instar to adult emergence has been documented to require nearly four years in related tiger beetles, suggesting potentially prolonged larval development in Omus. Pupation occurs within the burrow.

Strictly nocturnal, actively foraging at night. Adults are capable of rapid running but cannot fly. Mating behavior involves male-superior mounted amplexus with exceptionally prolonged copulation durations: 10.6±1.8 hours in O. audouini and 29.4±5.6 hours in O. dejeanii. Syn-copulatory courtship has been proposed as a female-choice reproductive mechanism. Niche partitioning through morphological character displacement occurs between sympatric species.

Conspicuous predators within terrestrial arthropod communities, occupying predatory roles in forest floor and salt marsh food webs.

Subject to conservation concern in Canada; Omus audouini is listed as a species at risk with limited distribution in southwestern British Columbia. Habitat mapping using indicator plant species (Douglas aster) has been developed to locate unknown populations and assess potential habitat.

• AmblycheilaBoth genera are flightless, nocturnal, and have large body size, but Amblycheila larvae have only two pairs of abdominal hooks with distinctly separated middle and inner hooks, and adults are significantly larger with reddish elytral coloration
• CicindelaSympatric tiger beetles that are primarily diurnal, possess functional wings for flight, and have larvae with only two pairs of abdominal hooks; larval burrows often show distinctive engineering modifications absent in Omus
• TetrachaNocturnal tiger beetles with similar activity period, but possess functional wings and larvae have two pairs of abdominal hooks with middle and inner hooks touching at the base rather than separated

• flightless
• nocturnal
• west coast endemic
• tiger beetle
• salt marsh
• forest floor
• prolonged copulation
• conservation concern
• Canada species at risk
• morphological character displacement
• Amblycheilini
• Cicindelinae
• Carabidae
• Coleoptera
• larval burrows
• Douglas aster indicator species
• niche partitioning
• male mandible dimorphism
• syn-copulatory courtship
• rain shadow habitat
• Sierra Nevada
• Cascade Range
• Coast Range
• British Columbia
• Oregon
• California
• Washington

• BugGuide
• Wikipedia
• GBIF taxonomy match
• iNaturalist taxon
• NCBI Taxonomy
• Catalogue of Life
• A rare opportunity to do fall insect collecting in western North America | Beetles In The Bush
• Amblycheila cylindriformis on white | Beetles In The Bush
• Diversity in Tiger Beetle Larval Burrows | Beetles In The Bush
• How to collect larvae of Amblycheila cylindriformis | Beetles In The Bush
• The Coleopterists Bulletin | Beetles In The Bush
• Distribution and Conservation Status ofOmus submetallicusG. Horn and Its Confusion withOmus californicus leconteiG. Horn (Coleoptera: Carabidae)
• Ecomorphology and Mating Behavior of Two Species of Night-stalking Tiger Beetles, Omus audouini and O. dejeanii
• Plant communities associated with a species at risk: Omus audouini (Coleoptera: Cicindelidae) in upper salt marsh habitat at Boundary Bay, British Columbia