Genus Stenosternus (Scarabaeidae, Orphninae)

Orphninae, Stenosternus costatus Karsch, 1881

Genus Stenosternus Karsch, 1881


Type species: Stenosternus costatus Karsch, 1881, by monotypy.


Body mid-sized (length 16.1 mm, pronotum width 7.3 mm, elytra width 7.6 mm), uniformly dark-brown with slight bronze and greenish tint. Mandibles subsymmetrical. Clypeus emarginate anteriorly, with crenate margin, without tubercles. Pronotum trapezoidal, elongated, with distinct longitudinal middle depression from base to almost anterior margin. Propleurae with fine carinae separating anterolateral areas from basal area adjacent to bases of elytra. Scutellum 1/20 length of elytra, narrow, rounded apically. Elytra somewhat oblong, 1.2 times longer than width, without striae but each elytron with low longitudinal ridge from base to about 5/6 its length. Wings vestigial, about 1/2 length of elytra. Metepisternon narrow, almost parallel-sided, with rounded distal part which somewhat overlaps epipleuron. Anterior tibiae relatively slender, almost parallel-sided, with 3 short outer teeth; protarsi absent. Middle and hind legs reduced to spur-like basal tarsomere. Phallobase symmetrical, with sclerotized ventral plate separated by weakly sclerotized membranous areas. Apices of parameres with tooth-like rounded processes directed anterolaterally and relatively long and dense pale setae. Lateral sides of parameres with short, sparse, mostly abraded setae. Medial sides of each paramere without membrane in apical 2/3 but with dense, scale-like teeth directed apically. Endophallus with about 15 small, tooth-like spinules, without larger sclerites.

Species composition. Only one species is known.


Endemic to São Tomé island in the Guinea Gulf.


Karsch, F. (1881) Uber von Herrn Professor R.Greeff auf den Guinea-Inseln gesammelte Coleopteren. Sitzungsberichte der Gesellschaft naturforschender Freunde zu Berlin, 55-62.

Karsch, F. (1887) Altes und Neues über Koleopteren. Berliner Entomologische Zeitschrift, 31, 1-8.

Frolov, A. (2013) Stenosternus Karsch, a possible link between Neotropical and Afrotropical Orphninae (Coleoptera, Scarabaeidae). ZooKeys, 335: 33–46.

Frolov, A. V. & Akhmetova, L. A. 2015. Rediscovery of the enigmatic Stenosternus costatus Karsch (Coleoptera: Scarabaeidae: Orphninae) from São Tomé island. Zootaxa, 4007, 440–444.