Omorgus suberosus

Beneficial

Common name(s)

none known

Taxonomy

Family: Trogidae Subfamily: Troginae Genus: Omorgus Species: Omorgus suberosus (Fabricius, 1775)

Adult diagnosis

Total body length 11.1–14.1 mm (0.44–0.56 in). Body shape oval; surface rough and warty, often dirt encrusted. Venter flat, dorsum convex in lateral view. Color dark grey-brown. Pronotum with base scalloped, basal angle obtuse. Scutellum hastate, never rounded. Elytra with dense patches of tomentose greyish hairs. Middle tibia lacking numerous fine teeth along outer margin.

Larval diagnosis

Undescribed. For Omorgus spp. (Ritcher, 1966): Grub C-shaped, not hump-backed, cylindrical, whitish. Maxilla with galea and lacinia distinctly separated. Antennae with 3 segments, lacking distal sensory cone on second segment. Distal segment of antennae much reduced in size. Epipharynx with tormae united mesally. Legs 4-segmented, never with stridulatory organ. Spiracles cribriform.

Native range

The Americas and Oceania. This species is found through much of the Americas, from Canada to South America. In the contiguous U.S., it is absent only from New England and the Pacific Northwest (Ratcliffe and Paulsen, 2008). It is also widespread throughout Australia and the Pacific Islands (Zidek, 2013).

Plant host(s)

None. Both adults and larvae of this species feed on late stage carrion and other dry animal remains, thus posing no threat to crops or ornamental plants.

Life history

Poorly known. This species is known to feed on late stage carrion (Ratcliffe and Paulsen, 2008). In Hawaii, it has been found feeding on discarded chicken remains at poultry farms on Oahu (Toyama and Ikeda, 1976). In temperate areas, this species overwinters as an adult. Adults can be collected at lights at night and are likely nocturnal. In Nebraska, adults have been collected from April until October (Ratcliffe and Paulsen, 2008). Reports of this species feeding on grasshopper eggs (Schistocerca spp.) are likely erroneous (Hawaiian Entomological Society, 1977).

Pest potential

None. This species recycles carrion and poses no threat to crops or ornamental plants.

Status in Hawaii

Established. While it is not clear when this species first arrived to the state, the first specimen was found in 1970 on Oahu (Hawaiian Entomological Society, 1977). Specimens have since been taken at Kahuli on Maui in 1986 (Hawaiian Entomological Society, 1989) and at Moloa'a Bay on Kauai (Asquith and Messing, 1993).

Status in Guam

Established. This species is established on Guam, where it is the only recorded hide beetle (Bourquin, 2002). How or when it came to the island is unknown.

Potential distribution and dispersal pathway

It is unclear how this species arrived in Hawaii or Guam. This scarab is attracted to lights at night, thus it is possible that adult beetles fly to well-lit ports or airports where they hitchhike on cargo. Indeed, in 1972, a specimen was taken at a light trap at Pearl Harbor Hickam Air Force Base, possibly suggesting aircraft-mediated dispersal (Hawaiian Entomological Society, 1974).

Similar species

Omorgus suberosus is one of three hide beetles (Trogidae) known from Hawaii and Guam. The other two species are Trox scaber and Omorgus procerus. These species are separated by size (both Omorgus species are over 10.0 mm [0.39 in] versus Trox scaber at 5–7 mm [0.19–0.28] and examining the pronotum (O. suberosus with a scalloped base and obtuse basal angle versus T. scaber with a weakly sinuate base and quadrate basal angle), scutellum (O. suberosus with scutellum hastate versus T. scaber with scutellum rounded), and middle tibia (O. suberosus with middle tibia lacking numerous fine teeth along lateral margin versus O. procerus with numerous, fine teeth).

Other names (synonyms)

Omorgus punctatus LeConte, Omorgus triestinae Pittino, Trox alternatus Say, Trox crenatus Olivier, Trox denticulatus Palisot de Beauvois, Trox gibbus Olivier, Trox ovatus Palisot de Beauvois, Trox manilensis Schultze, Trox nobilis Wollaston, Trox novaecaledoniae Balthasar, Trox suberosus Fabricius, Trox torressalai Baguena, Trox tricolor Blackburn, Trox tuberosus Laporte (Comte de Castelau)

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Omorgus suberosus; photo by E.L. Engasser

Omorgus suberosus; photo by E.L. Engasser

Omorgus suberosus; photo by E.L. Engasser

Omorgus suberosus; photo by E.L. Engasser

distribution map for Omorgus suberosus

distribution map for Omorgus suberosus