Disguise master rarely seen

The South Island lichen moth, Ipana egregia (family Geometridae, subfamily Ennominae), is one of our most beautiful and iconic insects. Fittingly, it features on the New Zealand $100 note.

The female, slightly larger than the male, has a wingspan of about 63mm, while the male’s wings are about 55mm across. The caterpillar feeds on five finger (Neopanax arboreus) and related shrubs, as well as lancewood.

As the moth emerges very late at night, often after midnight, it is seldom seen — unlike most moths, which, emerging early in the evening, are readily visible to people when the moths are attracted to lights.

The cryptically coloured and shaped caterpillar resembles a bird dropping when young and a Pseudopanax fruit when older, likely as a defence against birds and lizards. Large, older larvae look like lichen-covered twigs and hold themselves out at an angle from the branch stem. The moth overwinters on the forest floor as a pupa, protected and disguised within a thin, dirt-covered cocoon.

The caterpillar of the South Island lichen moth can be readily seen in Woodhaugh Gardens, North Dunedin, where it occurs in this small but never-felled kahikatea swamp forest relict with a particularly large and valuable suite of native invertebrates, many in leaf-litter on the forest floor.

— Anthony Harris is a curator at Tūhura Otago Museum