Bush fly population explodes in Central Australia as hot, humid weather creates perfect breeding conditions

It’s not hard to spot the flies around Alice Springs at the moment. (Supplied: Charlie Cowan)

Hot, wet conditions to the north and east of Central Australia have provided the perfect breeding conditions for bush flies in the red centre.

Theo Evans, associate professor of applied entomology at the University of Western Australia, says the flies are very mobile.

“They can beat their own wings and their own muscle power and fly perhaps 10 kilometres a day,” Dr Evans says.

“But they can also fly quite high, hundreds of metres up into the air. And there’s strong winds at that height.”

He says according to recent CSIRO research, the flies can also be blown more than 300km a day.

“That is normal,” he says.

Dr Evans says it is too cold for the flies in the southern half of the continent in winter.

“Flies can’t survive below 15 degrees.”

But they can survive in the warmer climates in the northern half of Australia.

High-quality poo

Dr Evans says flies lay their larvae in animal dung but not all manure is suitable.

“Poo comes in different levels of quality,” he says.

High-quality poo comes from cattle, sheep, goats or horses, Dr Evans says.

“They lay their eggs lovingly into animal dung because their larvae eat poo.”

But conditions can get too wet for the flies to survive.

“The maggots can actually drown in their delicious poo,” he says.

The warmer it is, the faster flies develop.

“These flies grow really well at any temperature above 28,” Dr Evans says.

“From egg to adult can happen in six or seven days.”

Dr Evans says flies typically live up to three weeks.

“But the hotter it gets, usually the shorter their life.

“They don’t actually need to eat a lot of food because they did most of their eating of food when they were babies.”

However they are always on the hunt for water and salt.

“That’s why they come to us and other animals,” Dr Evans says.

“You’ll see livestock, camels and so forth getting pestered by flies and when do they come, they normally go to your eyes and nose and your mouth.”

Sensitive to temperature

Flies are sensitive to extreme heat, Dr Evans says.

“They just think it’s too hot and find a little crawly, hidey-hole space where it’s a bit cooler.

“They’ll avoid that really hot part of the middle of the day, and then they’ll come back out again and disappear by the evening.”

But a cold snap will “do more harm” than a hot spell, Dr Evans says.