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ABC News
ABC News
National

Victoria's wet few years contribute to booming dragonfly population

Dragonfly populations are booming in Victoria, with swarms of the colourful insects emerging from ponds, pools and waterways thanks to weather conditions that favour their breeding patterns.

Dragonflies lay their eggs in bodies of water, where they often float all the way to the bottom before eventually hatching.

Senior curator in entomology at Melbourne Museum Richard Marchant said dragonflies usually took "about a year" to develop as larvae, before turning into adults.

He said he had heard many recent reports of increased dragonfly numbers, particularly around Melbourne's coastal suburbs.

"A good long spell of wet weather, as we've had all last year and a lot of the year before, has probably made the habitat very favourable to them," Dr Marchant told ABC Radio Melbourne.

He said the breeding boom was taking place in areas spread all across Victoria.

"They [dragonflies] are good indicators that you're dealing with a reasonably healthy aquatic ecosystem. The larvae rely entirely on small invertebrates which they eat and prey on," Dr Marchant said.

"It means the environment has to have been healthy for at least a year or so beforehand, before you see them as flying adults, because they've got to survive that period before they turn into adults."

He said there were more than 300 dragonfly species in Australia.

Record rainfall in spring, but it's likely to ease off 

With extremely wet weather over recent months, dragonflies are likely to keep hatching at higher than usual rates for a while to come.

A statement from the Bureau of Meteorology said during spring last year, Victoria's rainfall for the season was the highest "since records began in 1900."

Senior Forecaster at the Bureau of Meteorology Simon Timcke said the conditions were largely due to the La Niña weather pattern.

"That pattern is weakening now… and that generally means we'll start to see a decreased chance of above average rainfall," he said. 

"Looking at the longer range forecast for the next few months, February to April… there's not any strong signal to indicate above average rainfall expected, other than about the far east of the state."

Damselflies numbers also booming

Damselflies are the lesser-known cousins of dragonflies that are also hatching across the state.

Dr Marchant described damselflies as a "thinner, more delicate" version of a dragonfly.

"They're all part of the same group, called the Odonata, which is a major order of insects. It's split into two suborders if you like, and one is the damselflies and the other is the dragonflies," he said.

"The dragonflies tend to be the larger, more robust insects."

He said when dragonflies were still, they held their wings out to the side, while damselflies held their wings over their backs.

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