The first new species of Australian butterfly to be discovered in eight years has finally been identified after it was first photographed in 2017.
The spotted trident-blue butterfly – or cyprotides maculosus – is normally found in high altitudes in southern ACT and adjacent areas of New South Wales, in the areas of Namadgi and Kosciuszko National Parks.
CSIRO National Insect Collection Associate Professor Michael Braby described the discovery as "significant".
He said it was not uncommon to find new variants of butterfly species or subspecies, but this was something different altogether.
"To turn up something completely new, that's quite rare. That doesn't happen too often," he said.
"The last one was eight years ago in 2015, so to have it on our doorstep of the ACT – just 50 kilometres from Canberra – is really quite remarkable."
He said discovering a new species like the spotted trident-blue highlighted how incomplete the knowledge of local biodiversity was.
"Butterflies, compared to other insects, they're pretty well known," he said.
"We estimate more than 90 per cent of the butterflies are described in the taxonomic inventory, it's pretty close to completion.
"The fact that we can find a new species just on our doorstep, that highlights that the inventory of our biodiversity hasn't been fully catalogued or studied."
'Why on earth has this thing been overlooked for so long?'
Associate Professor Braby said the first photo of the spotted trident-blue – which was taken in Namadgi National Park by a citizen scientist – left him "a bit suspicious" that what he was seeing might be a new species.
Then in 2019 the first specimen was collected at Kosciuszko National Park by one of his colleagues, Justin Armstrong.
"These individuals had very large spots, so that sort of rang some alarm bells, but there were some other differences too," he said.
"The underside colour was much paler – they had a lot more yellow on the underside of the forewing – and the other side is this brilliant coppery sort of bronze colour, whereas the other species is much more purpley-pink."
In 2020 and 2021, Associate Professor Braby went looking for the butterflies' breeding habitat and what their food source was, and found the answers to his questions in subalpine frost hollows.
"They live in these very specialised grassy frost hollows around the southern Namadgi and in the adjacent Kosciuszko National Park, and the altitude varies from about 1,100 metres up to 1,500 metres," he said.
"[Frost hollows are] these natural grassy plains. Cold air is denser than warm air, so it falls down the mountain and basically fills these valleys and keeps them very open and grassy."
Associate Professor Braby said the spotted trident-blue butterfly made its home in these frost hollows because they contained the plant they eat and lay eggs on, the hakea microcarpa.
He said during experiments he found the caterpillars were willing to eat plants that were related to hakea microcarpa when in captivity, but female butterflies would not lay their eggs on anything but that specific plant.
Associate Professor Braby said their strange habitat and unconventional flying schedule likely contributed to the spotted trident-blue butterfly not being discovered earlier.
"We were thinking 'why on earth has this thing been overlooked for so long? Why has it taken so long for people to discover this?' and we suspect it's a combination of the fact that it flies fairly early in the year and it's in this very specialised habitat," he said.
"It's not the sort of the place you'd really go to look for butterflies.
"They also fly quite early. It's around about springtime [around] October, November, when most insects in Namadgi don't really start flying until the summer months."
