Othnonius batesii Olliff, 1890

Allsopp, Peter G., 2022, Australian Melolonthini (Coleoptera: Scarabaeidae: Melolonthinae): reclassification of eight species to Antitrogus Burmeister, 1855 and Barryfilius new genus, Zootaxa 5213 (5), pp. 513-545 : 515

Placement of Othnonius batesii Olliff, 1890

Olliff (1890) described O. batesii listing four localities in inland New South Wales. Apart from reports of its larvae as a pest on the Darling Downs of southern Queensland and in inland New South Wales in the late 1960s ( Turner & Shaw 1969; Turner & Roubicek 1970; Goodyer 1977), the species remained largely forgotten until Britton’s (1978) revision of the Australian Melolonthini . Blackburn (1911, 1912) did mention that Olliff had described it, but, although he had specimens, he did not include it in his 1911 key to the genera of Melolonthini . Britton (1978) retained it as a valid but monotypic genus and added that larvae are serious pests “of pasture and a variety of crops in the black-soil country of inland New South Wales ”. This generic arrangement was continued by Houston & Weir (1992) and Weir et al. (2019).

Antitrogus Burmeister, 1855 is Australia’s second-most speciose genus of Melolonthini with 23 known species ( Allsopp 2003 ; Weir et al. 2019). The genus occurs only in eastern Australia ( Allsopp 2003 ) and is characterised by having an antennal club of 3–7 lamellate antennomeres in males; and the head, pronotum, elytra, and abdomen clothed with short setae, bare, or with minute setae that lie largely within their punctures, or with long, sparse, irregularly distributed setae, rarely with a few, larger, flattened setae in a group either side of a midlongitudinal line on the posterior half of the pronotum (never with scales or other flattened, adpressed setae) ( Britton 1978; Allsopp 2003 ). Antitrogus species also have symmetrical or near-symmetrical parameres.

Britton’s (1978) characterisations of Othnonius and Antitrogus show considerable overlap: absence of scales or flattened, adpressed setae; dorsal surface bare or with minute setae contained within punctures (sometimes sparse longer setae in Antitrogus ); antennal club in males long, 6 lamellate in Othnonius and 3–7 lamellate in Antitrogus ; antennal club in females short; anterior face of clypeus deep, ratio of greatest width to mid length 3.3–4.8: 1 in Antitrogus and <4.5 in Othnonius ; the shape of the male aedeagus (compare Fig. 8 with Britton’s (1978: figs. 23–73)). The only character that Britton (1978) used to separate the two genera appears to be that in Othnonius “the sutures between the abdominal sternites are not partly obliterated in the middle”, whereas in sternites 3–5 of Antitrogus they are “fainter in the middle than at the sides”. The colour pattern of O. batesii is similar to that of A. carnei Britton, 1978 , and Allsopp & Lambkin’s (2006) strict consensus of the two most parsimonious trees from an analysis of combined adult, larval and ecological characters of 22 Australian pest Melolonthini places O. batesii within a cluster of four Antitrogus species.

Given this overlap in distribution, overlap in generic characters and the absence of a clear distinguishing feature, I consider that O. batesii does not warrant a separate genus.

Figures

FIGURES 7–8. Antitrogus batesii (Olliff, 1890), male. 7, Dorsal view; 8, aedeagus, ventral, dorsal and lateral views. Fig. 7 reproduced from Weir et al. (2019) (CSIRO, used with permission). Fig. 8 reproduced from Britton (1978) (CSIRO, used with permission).