Fauna of New Zealand, No 82: Declana and Ipana (Insecta: Lepidoptera: Geometridae: Ennominae)

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Language: English with bilingual summary in English and Maori

Looper moths (family Geometridae) get their name from the characteristic 'looping' mode of locomotion of their caterpillars, which alternately bend their bodies in a semicircle and stretch themselves out straight as they progress. Loopers are a huge family of moths distributed worldwide, with more than 23,000 species; there are over 280 species known from New Zealand, almost all of them endemic to this country.

This volume covers one small group of New Zealand looper moths, but possibly the most spectacular in terms of size and wing patterns. The 'zebra moths' and their allies belonging to the genera Declana and Ipana are medium-sized to large, robust moths with densely 'furry' bodies. There are 15 species, 4 of which are described as new in this book. The North Island and South Island Zebra Moths (Ipana atronivea and I. egregia) are amongst New Zealand's most famous moths, with their striking black and white wing patterns, which nevertheless provide excellent camouflage against lichen-covered tree trunks. The South Island Zebra Moth is even featured on the New Zealand $100 note. Both these moths have extraordinary caterpillars, which mimic fungus-covered twigs of their host plant, Pseudopanax (five-finger and relatives). Another spectacular species is Ipana glacialis, the only truly alpine member of this group. It has strongly patterned reddish brown and white forewings and bright orange hindwings; males fly by day and are often conspicuous on sunny days above the treeline in their South Island habitats. Other species, such as Declana floccosa and I. leptomera, are amongst our commonest forest moths, occurring throughout the country. Declana floccosa is particularly interesting because of the extreme variability in its wing pattern: some specimens are almost unicolorous greyish, while others have dark spots or speckles, various lines and sometimes bright orange markings closely resembling lichens.

Some species of Declana and Ipana are very specific in their choice of host plant; for example, caterpillars of Ipana glacialis will only feed on species of Dracophyllum and those of I. griseata only on mistletoes (family Loranthaceae). On the other hand, caterpillars of Declana floccosa, Ipana junctilinea and I. leptomera are highly polyphagous, and will feed on plants in many different families.

Two species are of special concern from a conservation perspective. Declana nigrosparsa occurs only in the diminishing areas where its host plants, small-leaved species of tree-daisy (Olearia) are common. Much rarer still, Ipana perdita is currently only known from a single tiny area of forest in the far north of Northland at Te Paki. Its host plant is unknown, but may be the rare conifer Halocarpus kirkii.

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