Rhopaea Erichson, 1847

Sub family: Melolonthinae / Tribe: Melolonthini / Genus: Rhopaea

Medium to large beetles, body length 19-30mm. Body colouration typically yellowish brown to dark brown. Body covered in short setae, densely covering metasternal areas. Scales never present. Anterior and posterior borders of pronotum bearing long fringes of setae, overlapping onto frons and scutellum. Antennae 10 segmented with a 5-8 segmented lammelate club that are significantly longer in males. Anterior face of the clyeus pushed back, allowing labrum to commonly be viewed from above, covered in setal bearing punctations over its entire surface. Clypeal apex appearing subquadrate with rounded edges, sometimes slightly emarginate. Abdominal ventrites with sutural lines diffused medially. Tarsal claws with a median tooth.

There are 10 described species of Rhopaea. A key to species is provided by Britton (1978).

It is placed within the tribe Melolonthini which share the following features:

Abdominal sternites at least partially fused, sutural lines present between sternites, even when fused. Meso and metatibia with 2 spurs placed below the tarsal articulation. Tarsal claws usually equal and toothed. Antennae 9 or 10 segmented (rarely 8), Antennal lamellae 3-7 segmented. Labrum located below clypeus, distinct. 5th abdominal sternite and propygidium separated by a suture. Protibia with apical spurs.

An updated key to the Australian genera of Melolonthini is provided by Weir et.al. (2019).

Key distinguishing features are the antennal clubs of 5-8 segments (much longer in males), presence of setae over entire body (never scales), and the anterior face of the clypeus being quite flattened and covered in setose punctations. The long hairs on the anterior and posterior pronotal margins are also useful Genera defining characters.

Larvae of some Rhopaea species, particularly R. magnicornis, are root feeding pests of pastures, sugarcane, peanut, pineapple, wheat, glycine and hoop pine (Araucaria cunninghamii). Sugarcane damage can also spread into the base of the stalks.

Adult beetles do not feed. Females usually remain at their place of emergence and emit pheromones to attract the males. Females are hence much less commonly collected.

Rhopaea are only known from Australia, ranging from Queensland to South Australia.

Rhopaea magnicornis PaDIL image sets: http://www.padil.gov.au/pests-and-diseases/pest/main/135694

Britton, E.B. 1978. A revision of the Australian chafers (Coleoptera: Scarabaeidae: Melolonthinae) Vol. 2. Tribe Melolonthini. Australian Journal of Zoology, Supplementary Series 60, 1–150.

Chadwick, C.E. 1970. Some aspects of the life history and ecology of Rhopaea magnicornis (Coleoptera: Scarabaeidae). Proceedings of the Linnean Society of New South Wales 95, 11–25.

Miller, L., Allsopp, P. 2000. Identification of Australian canegrubs (Coleoptera: Scarabaeidae: Melolonthini). Invertebrate Taxonomy Vol 14: 377-409.