August 2006. The larva of this beetle was found feeding on Ludwigia spp. (Ludwigia spp. belongs to the Primrose Family – a common perennial weed in wetlands) at Koronivia Research Station, Fiji. The impact on the weed is quite substantial: the larvae defoliated the plant. The insect’s larval stage seems to have more than three instars with the largest about 7-8 mm in length. The adult is black and about 5 mm in length. The yellow/orange eggs are laid in clusters.

Members said that it was Altica corusca (Erichson). It is already reported from Fiji, in Hinckley’s list of Fiji pests on Jussiaea – a former name for Ludwigia. Others it might be Lema (perhaps L moribunda) or another Criocerine (Chrysomelidae).

A note from the Australian Museum, Sydney: it might be ‘corusca‘, but difficult to tell without examining male genitalia. There is a lot of confusion about correct names in this genus – corusca could be a synonym of one of the widespread southeast Asian species e.g., cyanea as there is a suspicious non-overlap of distribution, but the same host plant. Corusca is regarded as the correct name for the Pacific island populations, because of Samuelson’s revision for the Pacific region (1973), but it was originally described from Tasmania, and the Australian species have never been revised.