Swarms of hungry dragonflies have descended on Adelaide after a "perfect storm" of mild and wet conditions caused the population to boom.
And the "predatory pest controllers" are on the hunt for mosquitoes.
Science educator Kris Messenger told ABC Radio Adelaide there were "substantial dragonfly numbers" appearing across South Australia in December last year and into January after heavy rainfall in central Australia.
She said the record rain in regional South Australia earlier in the year had allowed the population to skyrocket over past 11 months.
"They've now come to visit us in the city," she said.
"What's happening is, we've had this prevailing and persistent mild weather, and it's been coupled with lots of rain, it hasn't been too hot or too cold.
"A lot of that rain has been statewide and it stuck around and so places that should have been dry for six months have remained quite wet.
"That matters, because part of the dragonfly's life cycle is aquatic, so they lay their eggs in water."
Ms Messenger said there had to be enough water around to "set up the dragonflies to be able to produce such big numbers".
Dragonflies 'predatory pest controllers'
She said Australia had 300 species of dragonfly, but the one she was seeing the most around Adelaide was the Australian emperor dragonfly.
"Last January, we spoke about a perfect storm, and that's exactly what we've got," she said.
"These dragonflies have been out around the state, breeding up in all this water, and now they're in big numbers and they need to eat.
"So these are probably feeding swarms that we're seeing."
Ms Messenger said a big weather event like a flood was flushing out a lot of insects, and the dragonfly diet included mosquitoes.
"When you've got water, weather and food in the right parametres, you're going to get tonnes of dragonflies.
"They are hands-down, good bugs — they're predatory pest controllers."
