Carabidae, Coleoptera, Insecta, Arthropoda, Animalia
Additional images: face view (click here), ventral view (click here).
Range:
British Columbia, Oregon and Washington.
Identification:
The genus Omus is part of the "tiger beetles," a group that used to be in their own family (Cicindellidae) but are now considered a part of the Carabidae. Tiger beetles are sharp-jawed insects, with distinct, sicklelike, toothed mandibles. The labrum is short. Long hairs are located near the inner edge of the eyes. The eyes are as wide or slightly wider than the pronotum. The antennae arise from the front of the head above the mandibles and are slender, with most segments much longer than wide. The antennae are filiform. The clypeus is produced laterally beyond the bases of the antennae. The elytra are punctate, with the edges sometimes faintly toothed. The legs are long. The metasternum has a transverse suture just in front of the hind coxae. The first visible abdominal segment is divided by the hind coxae. The hind trochanters are with large lobes. The tarsal structure is 5-5-5 (Borror, et al. 1989). In the males, 7 abdominal segments are visible, and 6 in the female (Comstock, 1920). The larvae are "S" shaped, with a hump bearing curved hooks on the 5th abdominal segment.
Natural History:
Tiger beetles in general are heliophilic. The habitat consists typically of open, sunny locations. They can be found on sandy beaches and trails, scattered vegetation, lake shores and stream banks. Some can be found on forest edges, in clay soils, and in rotten stumps. The larvae are found in vertical tunnels, often 0.3 meters underground in sandy and dry localities (Borror, et al. 1989). The larva's head protrudes slightly from the hole opening, the jaws wide apart, ready to capture insects passing by. The hooks on the 5th abdominal sternum are used as anchors to the burrow, to aid the larva's success when battling larger prey. When the prey is captured and subdued, it is then dragged down into the bottom of the underground cavity (Bland, 1978). The adults and larvae are both voracious predators, as their name suggests, feeding on a variety of small insects. They sometimes bite when handled. They are swift runners and their speed on the ground aids their predation ability. They are also rapid flyers, frequently flying close to the ground. They are difficult to approach due to their wariness, taking flight quickly.
Members of the genus Omus are nocturnal, while most Cicindela are diurnal (Comstock, 1920).
Literature Cited:
Bland, R. G. 1978. How to Know the Insects, 3rd Edition. Dubuque, Iowa, Wm. C. Brown Company Publishers.
Borror, D. J., Triplehorn, C. A., and Johnson, N. F. 1989. An Introduction to the Study of Insects, 6th Edition. New York, Saunders College Publishing.
Comstock, J. H. 1920. An Introduction to Entomology. Binghamton, New York, Vail-Ballou Press.
