Why Victoria’s sky is full of white butterflies, or cabbage moths

We call them cabbage moths but Victorians with a moth aversion will be relieved to know the white fluttering creatures in their backyards are actually butterflies. This is why there’s so many.

We call them cabbage moths but Victorians with a moth aversion will be relieved to know the thousands of white fluttering creatures filling the state’s skies right now are actually butterflies.

A mild winter and recent wet, humid conditions have delivered ideal breeding conditions for cabbage moths to flourish, and they are being reported in huge numbers across Melbourne, Ballarat, Gippsland and beyond.

Deakin University Associate Professor in zoology Philip Barton told News Corp “cabbage white” were like most butterflies and held their wings upright, together, when resting.

A resting white butterfly (cabbage moth). Picture: Shaun Viljoen

A cabbage moth comes in to land. Picture: Shaun Viljoen

A species introduced from Europe, when conditions were optimal they reached high numbers.

While the butterflies were harmless, in their green caterpillar form they could be a pest, eating and damaging some types of vegetables, including broccoli, lettuce, kale, and — of course — cabbage, he said.

“Only the caterpillars are a pest,” Prof Barton said.

The recent rise in numbers was mostly due to the Victorian weather.

Warmer conditions over winter and spring had increased the survival of pupae, and encouraged the emergence of adult butterflies, he said.

“Continued warm weather means the eggs hatch and caterpillars grow very quickly before they pupate and turn into yet more adults,” Prof Barton said.

“The warmth makes things a little faster and that means their populations can grow rapidly.”

A cabbage moth’s whole life cycle was usually completed in just three weeks, with each female moth able to lay about 150 eggs in her short lifetime.

Recent wet, humid conditions have delivered ideal breeding conditions. Picture: Alan Barber

The butterflies shouldn’t be a problem, but the caterpillars they emerge from may be. Picture: Shaun Viljoen

What to do about them?

“Nothing,” according to Prof Barton.

“This is a natural phenomenon and it will simply take its course,” he said.

“A few more weeks and the numbers will drop again, once it gets cooler.”

But if the caterpillars the moths are emerging from are proving a problem in the garden, experts appear to agree a few chooks in the backyard could be the best weapon.

Manually plucking the caterpillars off leaves and chucking them to the chooks — or letting them free range to do the work themselves — could reduce the number of hungry caterpillars.

Meanwhile, Victorians can simply enjoy the pretty sight of fluttering butterflies.

Commenting on Reddit about the huge numbers of cabbage moths, Victorians said they were across the state.

One person said they were at Chelsea beach “and there were so many butterflies they looked like snow”, while another said “my cat has been having the time of her life chasing, jumping up like an AFL ruck and trying to catch these butterflies. Sometimes she has success and the outcome is pretty brutal”.

Yet another person commented in Melbourne’s eastern suburbs, there were so many it was “almost like a plague”.

“Some of the roads near my house are littered with dead butterflies. Around 8am we probably had 50+ just in our backyard then I looked down the street and I could see hundreds,” he said.

“In Ireland, white butterflies were believed to be the souls of lost children,” said another.

But perhaps best summing up Victoria’s white butterfly invasion was this person:

“I think they look awesome, they are everywhere!”

Originally published as Why Victoria’s sky is full of white butterflies, or cabbage moths