Why are there so many moths? Bogong moths swarm Sydney, Illawarra and Central Coast

Anyone who has stepped outside in parts of NSW over the past few days may have noticed there are suddenly moths everywhere.

The insects are appearing in huge numbers across the State, with residents reporting them invading homes and cars, hiding in washing and swarming around outdoor lights.

Social media is now being flooded with videos showing just how many have descended on parts of NSW.

“I’ve never been so overwhelmed in my life this is terrifying they are huge,” one TikTok user said as she filmed about 100 moths clinging to her glass sliding door.

Others have shared videos of the insects covering windows, gathering around lights and flying through homes.

But the sudden influx is not a household pest infestation.

The insects being spotted across much of NSW are Bogong moths embarking on one of Australia’s great annual migrations.

Each spring, a new generation of Bogong moths leaves breeding grounds across southern Queensland, NSW and western Victoria and begins an extraordinary journey towards the Australian Alps.

The endangered moths can travel up to 1000km during the migration and are known to pass through major cities including Sydney, Canberra and Melbourne on their way to the mountains.

Zoos Victoria’s Moth Tracker program says the migration occurs from September to December, meaning the current influx has arrived right on cue.

And this year, the moths are certainly making their presence known.

Social media has been flooded with reports from NSW residents finding large numbers of the brown insects around their homes.

“They are everywhere!” one person wrote on an Illawarra radio station’s Facebook page.

“We had three in the house and two in Dad’s car today!” another said.

A video from Wildflower Nursery at Erina on the Central Coast explained the large amounts of moths.

“Noticed the millions of bogon moths around? They’ve been blown off course on their annual migration to the Australian Alps. We can help them get back on track by switching off outdoor night lights! They are endangered and essential nocturnal pollinators so they need our help!!”

One woman said she had escorted about six moths out of her house in a single night and had “no idea” how they were getting inside.

Another reported finding the insects tucked inside clothes that had been hanging outside to dry.

“They settled inside all my clothes that I had hung out to dry,” he wrote.

“I had to turn everything inside out and shake them off.”

Others reported seeing huge numbers gathering around flowering bottlebrushes, verandas and vehicles, while one bus passenger claimed there appeared to be about 1000 moths on a window.

The mass appearance may look alarming, but the return of Bogong moths in large numbers is significant after the species suffered an estimated 99.5 per cent population collapse.

The moth was added to the IUCN Red List as endangered in December 2021, according to Zoos Victoria.

Research has found Bogong moth numbers can fluctuate significantly between years, with prolonged drought in their breeding grounds linked to major declines in migrating adults.

A 2025 study involving Western Sydney University researchers also found prevailing wind patterns play an important role in the moths’ extraordinary migration.

Research published in Biological Conservation in 2025 found wind patterns could help explain the moths’ enormous journeys, with modelling suggesting some can travel between breeding grounds and alpine areas in as little as a single night.

Large numbers have also previously been pushed towards the NSW coast during their migration by strong westerly winds.

Bright lights can create another problem.

Bogong moths travel predominantly at night and artificial lights in towns and cities can lure them away from their journey, which is why they can suddenly appear in enormous numbers around homes and buildings.

Zoos Victoria recommends turning off unnecessary outdoor lights during the spring migration and closing blinds or curtains where possible.

Residents are also being encouraged not to kill the unexpected visitors.

Bogong moths are an important part of Australia’s alpine ecosystem and provide a crucial spring food source for the critically endangered Mountain Pygmy-possum.

The tiny marsupials emerge from months of winter hibernation just as the moths begin arriving in the mountains.

Bogong moths also feed on flower nectar as they travel, helping pollinate plants along their route.

The sight of large numbers therefore has some NSW residents celebrating rather than reaching for the insect spray.

“Awesome news!” one woman wrote. “They are endangered and a key food source at this time of year for the equally endangered Mountain Pygmy Possum.”

Another said she was “really pleased” to see the insects returning in such numbers.

“We need these pollinators,” she wrote.

For those less thrilled about sharing their homes with them, the good news is they are only passing through.

The moths are heading towards cool caves and rocky crevices in the Australian Alps, where they spend the warmer months before making their return migration towards their breeding grounds.

Anyone who spots one is being encouraged to photograph it and submit the sighting to Zoos Victoria’s Moth Tracker, which scientists use to monitor when, where and in what numbers the endangered insects are travelling.

And for the next few weeks, NSW residents may want to give the washing an extra shake before bringing it inside.