Like moths to a flame

Published 07 Dec 2017 

As the temperature dropped in the early hours of a May morning on Scottsdale Reserve, NSW, Glenn Cocking’s white sheet – wet with dew – began to freeze.

The sheet was suspended vertically between two metal rods, with a bright light shining on it to attract moths.

Hippotion scrofa moth. Photo Suzi Bond.
Hippotion scrofa moth. Photo Suzi Bond.
Glenn, a volunteer curator at the CSIRO’s National Insect Collection and self-taught moth expert, was carrying out Scottsdale’s first ever moth survey.

The value of moths in nature is often undervalued, if not completely overlooked. But this incredibly diverse insect order, known as Lepidoptera, underpins many food chains and ecosystems.

From birds to bats, lizards and small mammals, moths and their larvae are important food sources for many species, and they also help pollinate some native plants.

On that first night of surveying, Glenn recorded 99 different moth species, which he calls a relatively “small number” (there are thought to be about 22,000 species of moths and butterflies in Australia). When he returned to Scottsdale this year on a warmer night, he recorded 268 species.

“There are one or two species of moths that will fly around in the frost, but not many, so the difference in numbers is mostly because of differences in season and temperature,” says Glenn.

The moth survey setup. Photo Suzi Bond.
The moth survey setup. Photo Suzi Bond.
Scottsdale Reserve Manager Phil Palmer says the moth population on Scottsdale is likely supporting the region’s woodland birds, as well as reptiles like the recently reintroduced Striped Legless Lizard, small mammals like the Stripe-faced Dunnart, and bats.

“Scottsdale is increasingly being recognised as quite significant, both locally and regionally, for its very high reptile and mammal diversity in particular,” says Phil. “A lot of that diversity is probably underpinned by Scottsdale’s insect diversity, because insects are a food source for them.”

Scottsdale is restoration ecology in practice. Formerly cropped and grazed, Bush Heritage is now returning the 1328 hectare reserve, south of Canberra, to good health from the ground up. As more trees are planted and the landscape slowly transforms, Phil must think about how the ecosystem is functioning on every level.

“What we're trying to create is a rich and resilient reserve that can support many different animals,” says Phil. “It is one thing to give those animals habitat to return to, but you also need to make sure they have a food source.”

Take the woodland birds as an example, he says. There aren’t a lot of flowering plants on the Monaro high plains where Scottsdale is located, which means most of the birdlife in the region is insectivorous. In other words, without moths and other insects, those birds would starve.

“Moths are just one piece of the ecological puzzle,” says Phil. “But every piece is important.”

Thank you to Glenn Cocking and Suzi Bond, who assisted Glenn and took photographs, for volunteering their time and expertise to conduct these surveys.