• WU Team
  • 3 May 2024
  • 8:24 am
  • 0 comments

The butterfly and the ant - a wild relationship


Wildlife Unlimited staff have been searching the grasslands and open woodlands of northwest Victoria to find the elusive Mallee Bronze Azure butterfly (Ogyris subterrestris) and its host Sugar Ant (Camponotus terebrans).


There are only three populations of this endangered butterfly known in the world, one in Victoria’s far northwest near the Hattah Kulkyne National Park and adjoining private land; the other two in South Australia.

Captions (l to r): The Mallee Bronze Azure butterfly is ranked seventh on the list of Australian butterflies most likely to go extinct. This is a female . The host Sugar Ant with fresh butterfly eggs. The butterfly eggs are tiny! Much smaller than a matchhead. These eggs have hatched. All photos with thanks to Current Line Productions.

A butterfly that eats ants

It is not just rarity that draws us to this butterfly. Its lifecycle is crazy interesting. The butterfly is myrmecophagous – in other words, it eats ants! The Mallee Bronze Azure lays its eggs at the entrance to a nest within a huge Sugar Ant colony; possibly covering square kilometers! When the caterpillars hatch, they emit a chemical or pheromone that smells good to the host ants. The ants then take the caterpillar deep into their nest where it stays, safe from predators. But the ants are being tricked because the caterpillar is secretly eating the ant babies!

The caterpillar remains underground until spring when it emerges as a beautiful butterfly, which is about as big as the end of your thumb. When in flight, the butterflies appear black with the occasional flash of the brightest blue from the upper wings. When they land you can see the intricate patterning on the underside of the wings that provides their camouflage.

Impacts of the 2022 floods


Both the Victorian and South Australian populations of the butterfly were heavily impacted by the Murray River flood in late 2022. Flooding drowns colonies of host ants, butterfly eggs and caterpillars.


In early 2024, Wildlife Unlimited (WUL) was engaged to revisit the Victorian sites where the butterfly is known to lay eggs. One of our staff, Dr Fiona Murdoch (left), has been studying the butterfly for several years and first raised the alarm about potential impacts of flooding on this threatened species.

We found approximately 50% of these sites had been impacted by flooding, which is terrible news. Fortunately, we also found evidence that the host Sugar Ant has bounced back and appears to be recolonising the fringes of some previously flooded areas. We even found butterflies and fresh eggs in some locations, so all is not lost. Most excitingly, the keen eyes of WUL’s Jacinta Richardson discovered butterfly eggs in locations that weren’t previously recorded as breeding sites.


The ant-butterfly relationship


The Mallee Bronze Azure butterfly is totally dependent on its host Sugar Ant to raise the caterpillars. So, to look after the butterfly we need to look after the ant. But we don’t know much about it.


The Sugar Ant is widespread across southern Australia, from Western Australia to Tasmania. However, preliminary genetic analyses suggests that, across Australia, there might be more than one species of ant currently classified as Campotonotus terebrans, although they all superficially look the same. That could explain why the ant appears widespread, but there are so few locations where the ant hosts the butterfly. In other words, it is possible the host ant is much rarer than previously thought.


WUL was also engaged to collect samples of ants from northwest Victoria for CO1 barcoding. This technique provides a genetic fingerprint that helps reveal hidden diversity within taxa such as ants. Stay tuned as we try to unravel the true identity of the ant that hosts this very rare butterfly!

Captions: Top – Dr Fiona Murdoch on site. Middle - Female Mallee Bronze Azure butterfly showing a flash of the bronze and azure on the inner wing that it is named for. These butterflies always sit with their wings closed so it is difficult to share their full magnificence! Bottom Jacinta Richardson searching for eggs in new sites.

Thank you, butterfly-lovers


Research into the Mallee Bronze Azure butterfly has been jointly funded by the Australian and Victorian governments under Disaster Recovery Funding Arrangements. And a shout-out to the extraordinary Current Line Productions for providing their photography and videography services at a vastly discounted rate because they “reckon the butterfly is pretty cool”.