Orcus Mulsant, 1850: 465. TS: Orcus janthinus Mulsant, 1850.
Orcus (Priasus) Mulsant, 1850: 467. TS: Coccinella bilunulata Boisduval, 1835.
Parapriasus Chapin, 1965: 254. TS: Coccinella australasiae Boisduval, 1835.
Orcus can be distinguished from Halmus by its pronotum with marginal line along base broadly separated from the posterior edge, elytral epipleuron almost always with deep foveae to receive femora, 9-segmented (rarely 8-segmented) antenna and well developed ovipositor with distinct styli.
Length 2.8-5.8 mm. Dorsum glabrous; elytra black to blue or green sometimes with metallic sheen often with colour pattern. Head transverse; eye distinctly emarginate; temple distinct, shorter than eye. Antenna 9-segmented (rarely 8-segmented), short; scape asymmetrical; terminal antennomere longer than penultimate one (except in O. citri,). Clypeus short, weakly emarginate medially and extending laterally into eyes; labrum partially exposed. Maxillary palp moderately long, last palpomere somewhat expanded apically with oblique apex. Pronotal base entirely bordered medially, the bordering line continuing interrupted or uninterrupted laterally but always remaining separate from fine marginal line; prosternum moderately long in front of procoxae; prosternal process narrow, without carinae; hypomeral fovea sometimes present near anterior angles of prosternum. All tibiae simple externally, without apical spurs; claw strongly appendiculate to almost simple. Elytral margin weakly reflexed usually without clear bead; epipleuron descending almost always with deep foveae. Abdomen with 6th ventrite usually visible in male; postcoxal lines separated or joined at middle, each running parallel to posterior margin of ventrite or recurving apically. Male terminalia. Parameres and phallobase symmetrical; penis guide symmetrical. Parameres articulated with phallobase. Penis stout, consisting of single sclerite; basal capsule distinct and T-shaped. Apodeme of male sternum 9 very narrow and rod-like. Female terminalia. Coxities distinctly elongate, triangular; styli strongly reduced and hardly visible; infundibulum horn-like, with sperm duct originating at its base; sperm duct divided into two regions of different diameter. Spermatheca globular without clear cornu; spermathecal accessory gland adjacent to sperm duct.
Distribution and Biology
Oriental and Australian Regions with most species in New Guinea and Australia. Species of this genus are known to be predators of various scale insects.
Chapin, E. A. 1965. The genera of the Chilocorini (Coleoptera, Coccinellidae). Bulletin of the Museum of Comparative Zoology, 133(4): 227-271.
Gordon, R D. 1985. The Coccinellidae (Coleoptera) of America north of Mexico. Journal of the New York Entomological Society, 93(1): 1-912.
Mulsant, M.E. 1850. Species des Coléoptères Trimères Sécuripalpes. Annales des Sciencies Physiques et Naturelles, d'Agriculture et d'Industrie, publiées par la Société nationale d'Agriculture, etc., de Lyon, Deuxième Série, 2: xv + 1-1104 pp (part 1 pp. 1-450; part 2 pp. 451-1104).
Slipinski, A. 2007. Australian Ladybird Beetles (Coleoptera: Coccinellidae) their biology and classification. ABRS, Canberra. 286 pp.
Slipinski, A, and J. A Giorgi. 2006. Revision of the Australian Coccinellidae (Coccinellidae). Part 6. Tribe Chilocorini. Annales Zoologici (Warszawa), 56, (2): 265-304.
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