Researchers following the trail of an endangered carnivorous butterfly are hopeful ants' nests in the Goldfields and Wheatbelt regions of Western Australia will lead them to new colonies.

The arid bronze azure butterfly, Ogyris subterrestris petrina, recently had its conservation status upgraded to critically endangered by the federal Threatened Species Scientific Committee.

The elusive butterfly is so rare its only known living colony in the world is found at Mukinbudin, in the north eastern Wheatbelt.

Scientists from the Department of Parks and Wildlife are actively searching for the creature, which shares an extraordinary relationship with sugar ants.

Senior research scientist Matthew Williams said the butterfly lays its eggs beside the ants' nests, which caterpillars surreptitiously invade.

Dr Williams said it was among 1 per cent of butterflies worldwide that are carnivorous, as it feeds off the ants within the nest as it grows.

"It is a very unusual lifestyle for a butterfly," he said.

"There are few butterflies in the world that do it and it's a situation that's evolved.

"Caterpillars like to eat plants as their main food, but there are some caterpillars that have built up a relationship with ants, and the ants look after the caterpillars and the caterpillars produce a special excretion called honey dew, which the ants like.

"This butterfly has gone one step further - it has stopped eating plants and now just eats the ants themselves, or rather the ants' babies."

Ant nest data used to find new colonies

The arid bronze azure was first discovered in the 1980s near Lake Douglas, which is 12 kilometres south of Kalgoorlie.

In 1993 the butterfly colony disappeared, leaving scientists baffled, until a butterfly enthusiast saw a number of the bronze azures near Mukinbudin and collected a sample for testing.

Dr Williams said researchers were using existing data on ants' nests to try and uncover new butterfly colonies.

"What we really want to do is find more colonies of the butterfly," he said.

"With only one colony we don't know what will happen to it if there's a big fire for example, or if for some reason the ants, like they did at Lake Douglas, just disappear.

"So when we go and do our monitoring out at Mukinbudin we count how many butterflies we see in a fixed time period, but we also map the extent of the ant colonies.

"The ant itself is not particularly rare, but trying to find big colonies of it is quite hard."