Paropsisterna cloelia adults in eucalypt planting in Marlborough, New Zealand

The Eucalyptus variegated beetle, Paropsisterna cloelia (Stål) (Coleoptera: Chrysomelidae), a paropsine leaf beetle from Australia, is invasive in New Zealand and was first detected in 2016. The species’ colour polymorphism has historically caused uncertainty about its taxonomy. Over two consecutive growth seasons, adults of Pst. cloelia were collected off eucalypt trees at a field site in Marlborough, counted, and the elytra colour and rigidity recorded. The aim of the study was to find out whether true colour morphs exist in this species or whether elytral colour is due to age/maturity of the beetles. We found that the abundance of adults with different elytral colouration and rigidity was temporally restricted during the season. This strongly suggests that the colour and rigidity of elytra change as beetles maturate, starting with soft red, over hard red, hard green, and finally turning brown. However, this should be confirmed in a laboratory trial where development of individual beetles can be observed.