Omus audouini

Reiche, 1838

Audouin's Night-stalking Tiger Beetle

Omus audouini, commonly known as Audouin's Night-stalking , is a tiger beetle in the . It exhibits pronounced sexual size with females larger than males, and possesses that serve dual functions for capture and mating amplexus. The species shows partitioning with O. dejeanii through body size and mandible length differences following Hutchinsonian Ratios. It is of concern in Canada due to its extremely limited distribution.

Pronunciation

How to pronounce Omus audouini: /ˈoʊ.məs ɔːˈduː.ɪ.naɪ/

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Identification

Distinguished from O. dejeanii by body size (approximately 1.3x scaling ratio) and length (1.5x scaling ratio). The region of the mandibles (terebral ) shows -specific differences related to processing, while the region is sexually . In Canada, the only other Omus species is O. dejeanii, making identification relatively straightforward where ranges overlap. Presence can be indicated by Douglas aster (Symphyotrichum subspicatum) in upper salt marsh at Boundary Bay.

Habitat

Forest floor in forested areas; upper salt marsh habitat in southwestern British Columbia specifically associated with 15 m from flood-protection dikes dominated by Douglas aster (Symphyotrichum subspicatum). Habitat transitions from diverse near dikes to halophyte-dominated estuarine marsh at greater distances.

Distribution

West coast of North America; in the United States found along the west coast, while in Canada it is extremely limited to Boundary Bay and a small along the coast of Victoria Island in southwestern British Columbia. The Canadian represents a significant range disjunction and concern.

Seasonality

Nocturnally active as . Specific seasonal activity period not well documented in available sources, though night-stalking are typically active during warmer months.

Diet

captured and processed using ; the mandible region (terebral ) is specifically associated with prey processing. Specific prey items have not been identified in available literature.

Life Cycle

Larval biology presumably similar to other Omus , with creating burrows in soil. Detailed information including developmental duration and number not available in provided sources.

Behavior

with conspicuous role in terrestrial . Mating involves male-superior mounted position with notably extended duration averaging 10.6±1.8 hours—an of magnitude greater than other . Males use to grasp females and maintain amplexus during mating. Syn-copulatory courtship has been proposed as a female-choice mechanism. Time of initiation, food deprivation, and operational sex ratio do not significantly affect mating duration in laboratory conditions.

Ecological Role

within terrestrial . The ' activity pattern suggests it occupies a distinct temporal from .

Human Relevance

of concern in Canada due to extremely limited distribution. associations with Douglas aster (Symphyotrichum subspicatum) have been used to develop survey methods for locating previously unknown and mapping potential habitat. Subject of ecological research on partitioning and .

Similar Taxa

Omus dejeanii at Powell Butte Nature Park, Portland, Oregon; distinguished by body size (1.3x ratio) and length (1.5x ratio) following Hutchinsonian Ratios; mandible region differs in structure
Other Omus speciesApproximately 9-10 in Omus in western North America; O. audouini distinguished by geographic distribution and morphometric ratios where

More Details

Geometric Morphometrics

Geometric morphometric analysis has demonstrated that shape differs between sexes and in complex ways: the mandible region is sexually , while the region (terebral ) shows interspecific differences linked to processing.

Conservation Status

In Canada, the is considered at risk due to its extremely limited distribution restricted to upper salt marsh at Boundary Bay and a small area on Victoria Island. The strong association with Douglas aster (Symphyotrichum subspicatum) provides a tool for habitat mapping and surveys.

Mating System

The exceptionally long mating duration (10.6±1.8 hours average) distinguishes this from most other . The serve a secondary sexual function in addition to feeding, being used by males to grasp and maintain hold on females during amplexus.