Reason behind 'interesting' backyard discovery baffling Aussies: 'Noticed this lately'

Some Aussies have witnessed swarms of flies gravitating towards their clotheslines recently and wondered why it might be happening.

Swarm of blowflies sitting on a clothesline in an Australian backyard.
Aussies are baffled after witnessing a swarm of flies gravitate towards a clotheslines. Source: Reddit/GraciesMumma22

You'd be hard pressed to see an Aussie backyard without a pesky fly buzzing around, especially as we approach the summer months. But an observation made by one local this week had witnesses baffled.

"What’s with the flies lately? These are on our clothesline," said the resident online sharing a photo of their clothesline. It was covered by a swarm of blowflies perched effortlessly on the wires — and they're not the only one who's witnessed it.

Others admitted they've also "noticed this lately". "We’ve been getting enormous flies round here," said another. While someone else joked they're likely "line dancing".

And while it's not necessarily common blowfly behaviour, there are several reasons why it might be happening, a handful of experts told Yahoo News Australia.

Entomology researcher Dr Lucas Hearn agreed it's "definitely an interesting behaviour". "I wouldn't necessarily say flies are attracted to clotheslines in particular, but more so the clotheslines' positions," he said.

Often, they're located in the centre of a backyard away from obstructions like trees or the house itself. "It probably provides a nice, high spot to observe a wide area for food and also any potential predators," he added.

Swarm of flies sitting on clothesline in an Australian backyard.
There are several reasons why the flies might be doing this, experts said. Source: Reddit/GraciesMumma22

And while Dr Keith Bayless from the CSIRO agrees it's likely "a good vantage point to see predators coming and avoid them" entomologist Bryan Lessard, known as The Fly Guy, argued, generally, "flies aren't that smart".

"Flies usually get picked off by birds because they're not really scanning out for birds," he explained. "It could be a really good vantage point for the flies to look out for other flies". By that, he means females in search of males to mate with.

Lessard suggests another possible reason for the unusual behaviour, noting that flies like lizards, are cold-blooded and enjoy the sun.

"They might be hanging on the clotheslines like they would on a tree trunk to bask in the sun," he explained. "They can't regulate their body temperatures, so they do a lot of sunbaking to become warmer and more active. The clothesline could be the perfect perch for them to sunbake".

Finally, while it's not seen in the photo, if darker clothes are hanging from the line, the flies may be attracted to them. Lessard explained that it's true the pesky insects are attracted to black and blues as they tend to heat up more than other colours.

Love Australia's weird and wonderful environment? 🐊🦘😳 Get our new newsletter showcasing the week’s best stories.