Metatrogus Britton 1978

Transfer to Metatrogus Britton, 1978 Matsumoto (2008) examined the type series of H. burmeisteri, as well as additional specimens from Babelthuap, and transferred the species to the genus Metatrogus Britton, 1978. Metatrogus comprises four other species (Britton 1978; Allsopp 1999; Weir et al. 2019), all from eastern Queensland, Australia and 3200–4300 km south of Palau. Matsumoto (2008) based his transfer to the Melolonthina (now Melolonthini) mainly on the wing venation of H. burmeisteri and, presumably, on superficial similarities in the shape of the aedeagi but made no mention of examining any Metatrogus specimens. He curiously added “Britton’s definition of Metatrogus applies very well to this species [burmeisteri] except for the following points: (1) ‘hypopleuron’ of pronotum, abdomen, pygidium and propygidium without any adpressed white hairs; (2) anterior margin of pronotum rimmed throughout”. Comparison of the type series of H. burmeisteri and specimens of the four Australian species of Metatrogus (M. castaneus Britton, 1978, M. lukei Allsopp, 1999, M. praeceps Britton, 1978, M. septuosus Britton, 1978; specimens in QM) shows that this transfer was incorrect. Amongst other characters, H. burmeisteri has: unmodified, elongate setae (Fig. 9) on the venter, whereas Metatrogus have flattened, white, adpressed setae (Fig. 11); the labrum deeply indented and forming two lobes (Fig. 8), whereas Metatrogus has the labrum indented to less than half length and the indentation is broadly rounded (Fig. 10); the antennal club is of three lamellae, whereas it is of three, five or six lamellae in Metatrogus; the metepisternum narrow (ratio 5:1 to 6:1) and metepimeron small (Fig. 9), whereas the metepisternum is rhomboid and the metepimeron is larger in Metatrogus (Fig. 11); parameres where the apices do not cross over and without a basal backward projection on each (Fig. 19), whereas three of the Metatrogus spp. have the apices of the parameres crossing over, and all have a basal backward projection on each paramere (Britton 1978, figs. 74–82; Allsopp 1999, fig. 3). In essence, H. burmeisteri clearly keys to the Rhizotrogini, whereas Metatrogus falls within the Melolonthini (Lacroix 2010, pp. 19–20). No endemic Rhizotrogini are known from Australia (Weir et al. 2019).