Differences in foraging behaviour between Wiseana copularis (Meyrick) and W. cervinata (Walker) (Lepidoptera: Hepialidae) in exotic pastures

Abstract

ABSTRACT Porina (Wiseana spp.) are endemic to New Zealand with some species adapting to exotic pastures, where they cause significant damage. Porina larvae cannot be identified to species level in the field so the relative impact of each porina species is not known. Greater knowledge of foraging behaviour by different porina species will help to determine species-specific impacts. The nocturnal foraging behaviours of W. cervinata and W. copularis larvae were investigated in the laboratory using videos recorded under infrared conditions. Foraging behaviours were characterised, and videos analysed using BORIS software found species differences in the number of burrows constructed and in foraging choices. Behavioural sequences were similar for both porina species, with W. cervinata larvae foraging exclusively on white clover while W. copularis foraged on white clover and ryegrass. W. cervinata larvae constructed one horizontal burrow whereas W. copularis constructed 2–3 horizontal burrows to reach their food plants. By constructing several horizontal burrows, W. copularis larvae have access to more plants without exposing themselves above ground to adverse weather conditions or predators. This may be an advantageous strategy for W. copularis larvae, particularly at high population densities when food becomes scarce, and may increase the degree of pasture damage caused by this species relative to other Wiseana spp. Porina management should target the most damaging species within the complex and this study provides further evidence that W. copularis is more likely to cause pasture damage.