Trissodon

Trissodon australasiae, copyright Matthew Connors.

Belongs within: Dynastinae.

Trissodon is an Australian genus of dynastine beetles characterised by an apically contracted clypeus, broadly exposed mandibles, a transverse clypeofrontal ridge, and males with an anteromedian tubercle and small depression on the pronotum.

Characters (from Carne 1957): Small to medium sized (9-16 mm) dark reddish brown to black species. Mentum not compressed, disc setose, ligula weakly bilobed; maxillae with galeae 2–4-dentate, palps small. Antennae 9-, rarely 8- or 10-segmented, club shorter than shaft, the first 2 segments setose. Mandibles with simple ovate outline, strongly produced beyond clypeus; sometimes with an inner very short truncate tooth not visible externally. Clypeus abruptly truncate, often subapically constricted, lateral margins usually concave (viewed dorsally). Labrum often visible as a transparent ledge below apical truncated face of clypeus. Clypeofrontal ridge transverse (rarely posteriorly arcuate and giving rise to a small median tubercle); ocular canthi setose. Pronotum with basal ridge obsolete; scutellum rarely punctate but often with a weak longitudinal striole. Elytra with sutural striae never punctate; epipleurae with sparse lateral setae. Fore tibiae acutely tridentate; tarsi with fifth slightly longer than first segment, claws simple. Hind legs slender: femora sometimes with 2 sulci; tibiae unicarinate; tarsi occasionally, but not usually, with first segment asymmetrically dilated. Postcoxal process of prosternum inconspicuous, apex rounded or tapering, densely setose. Propygidium without stridulating ridges; pygidium usually glabrous, disc shining, apical ridge glabrous. Male with pronotum usually with anteromedian tubercle and small subcircular impression (except in those forms with cephalic tubercle); pygidium strongly convex. Genitalia of complex type. Female with pronotum evenly convex or with slight trace of an anteromedian swelling; pygidium slightly convex, or flat.

<==Trissodon Burmeister 1847 [=Isodon Hope 1837 non Say 1822] CW92
    |--*T. australasiae (Hope 1837) [=*Isodon australasiae; incl. I. terraereginae Blackburn 1896] CW92
    |--T. bryanti Carne 1957 CW92
    |--T. curtus (Burmeister 1847) [=Isodon curtus] CW92
    |--T. glaber Arrow 1914 CW92
    |--T. kiwanus Carne 1957 CW92
    |--T. laevigatus (Burmeister 1847) [=Isodon laevigatus] CW92
    |--T. laticollis (Burmeister 1847) [=Isodon laticollis] CW92
    |--T. nasutus (Blackburn 1896) [=Isodon nasutus] CW92
    |--T. setosus Carne 1957 CW92
    |--T. subopacus Arrow 1914 CW92
    |--T. tibialis Carne 1957 CW92
    `--T. tudor Carne 1957 CW92

*Type species of generic name indicated

REFERENCES

Carne, P. B. 1957. A Systematic Revision of the Australian Dynastinae (Coleoptera: Scarabaeidae). Division of Entomology, Commonwealth Scientific and Industrial Research Organization, Australia: Melbourne.

[CW92] Cassis, G., & T. A. Weir. 1992. Dynastinae. In: Houston, W. W. K. (ed.) Zoological Catalogue of Australia vol. 9. Coleoptera: Scarabaeoidea pp. 383–425. AGPS Press: Canberra.