Amphistomus primonactus description

Dung
Beetles
of eastern NSW

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Amphistomus primonactus

Distribution
Comboyne-Glen Innes area, New South Wales, in closed forest and Nothophagus forest, at elevations of 850-1200m.

Description
Total length 4-6mm. Colour dark brown.

Head: Dorsal parts of eyes very small.

Prothorax: Surface alutaceous, covered with large shallow punctures. Tubercles very prominent.

Elytra: Foreshortened. Tubercles along 1st elytral interval very small, mostly tufts. Intervals 3, 5 and 7 with very prominent tubercles. Pseudepipleura generally with 6 small tubercles. Lateral edges strongly serrate. Surface alutaceous. Striae fine to broad, superficial, with very large, closely spaced, shallow punctures.

Hind wings: Absent.

Sterna: Mesosternum with a strong median keel, usually long (about 3 times as wide as long). Mesometasternal suture fine and indistinct. Middle of metasternum strongly impressed, with a short keel behind mid coxa. Ventral surfaces densely covered with very large annular punctures.

Legs: Hind trochanter with a strong blunt tooth. Hind edge of middle femur strongly serrate. Hind femora with strong tooth two-thirds of way towards apex and a basal projection of hind edge near trochanter. Hind tarsal segments about as wide as long; 1st segment slightly shorter than 2nd and 3rd combined.

Abdomen: Sternites without tubercles. Pygidium with 1 very prominent tubercle at apex of disc and 2 in a transverse row medially.

Sexual dimorphism
Female: Clypeal teeth more prominent. Hind legs unmodified.

References
Matthews, E.G. (1974) A revision of the Scarabaeine dung beetles of Australia. II. Tribe Scarabaeini. Aust. J. Zool. Suppl. Ser. 24: 1-211. Williams, G. A. & Williams, T. (1983a) A survey of the Aphodiinae, Hybosorinae and Scarabaeinae (Coleoptera: Scarabaeidae) from small wet forests of coastal New South Wales. Part 2: Barrington Tops to the Comboyne Plateau. Vict. Nat. 100: 25-30.