Words: Georgia Beyer. Photos: Iain Stych.

As the last of the evening light faded from the sky above the tree canopy, red-tinted torches were switched on, casting an unreal glow around the forest. A small team led by Iain Stych from Envite was hopeful of a rare sighting of the southern pink underwing moth. Daytime surveys at the Eltham Big Scrub remnant had revealed over 70 of the moth’s caterpillars, and it’s likely there were many more hidden amongst the foliage. It was the perfect opportunity to see an adult moth. Or so it seemed.

The southern pink underwing moth (Phyllodes imperialis smithersi) is one of the many fascinating creatures that live in the Big Scrub rainforests. While the moth is quite large with a flash of bright pink on its lower wings, it’s only active at night and very hard to find in its dense rainforest habitat. It’s thought that the moths are shy of bright light making them harder to find. During the warmer months the caterpillars are more easily found than the adult moths by searching their host plant, the carronia vine (Carronia multisepalea).

Starting as tiny, almost transparent caterpillars a few millimetres long, they grow into large, 15cm, pinkish-orange caterpillars, often sitting on vine stems in the understorey. It must be a precarious existence being very slow to move and looking like a juicy feed for a bird, so it has some tricks to stay safe. The very young green caterpillars hide underneath leaves. As they grow, they become brown with darker markings to look like the dead leaves of their host vine plant. The larger caterpillars also have a spectacular warning display. When disturbed they curl their head down exposing a pattern on the back of their neck that looks like a scary face with teeth and large eyes.

When the southern pink underwing moth was first listed as nationally endangered in 2002, it was only known from five locations in southeast Queensland and northeast New South Wales. It’s now been found across many Big Scrub remnants and other areas of subtropical rainforest with a disjunct population near Bellingen. Recent studies have found that it’s more secure in the wild than earlier feared, which is great news. However, with its habitat restricted to subtropical rainforest and its larvae being reliant on only one species of host plant, we still need to look after this beautiful moth by protecting and restoring its rainforest habitat.

A current project by Envite Environment is assisting the recovery of the southern pink underwing moth through restoration of breeding habitat in critically endangered Big Scrub lowland rainforest remnants where weed invasion is a threat to the species. The project has enabled surveys for southern pink underwing moth larvae (caterpillars) which were carried out in Autumn earlier this year, finding over 200 caterpillars in 13 of the 19 remnants searched.

With such high numbers of caterpillars, the chance of seeing an adult moth at the Eltham site was too tempting to miss. So Iain and the team headed into the night with bags of rotten fruit, the moth’s favourite food, as lures that were hung in trees. Hours later, they had seen lots of caterpillars, some giant panda snails and a rainforest dragon by torch light, but no moths. A second night-time trip with more rotten fruit still couldn’t entice the elusive moths to show themselves. So where are all the adult moths? With so many caterpillars found, we know they are around. Have you seen any?

This project is supported through funding from the Australian Government.

Reference information:
Southern Pink Underwing Moth – NSW Threatened Species Profile: https://www.environment.nsw.gov.au/threatenedspeciesapp/profile.aspx?id=10625
Andren, M., Richards, P. G., & Sands, D. P. A. (2021). The Distribution and Ecology of the Southern Pink Underwing Moth Phyllodes Imperialis Smithersi Sands (Lepidoptera: Erebidae) in New South Wales. Australian Entomologist. 48. 133-148.