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From PestNet

Christmas beetles seem fewer in number. Citizen science aims to help explain why

ABC Far North
https://www.abc.net.au/news/2021-11-04/christmas-beetles-study-research/100587998

By Phil Brandel

For many, Christmas means Mariah Carey songs on repeat, hot weather and flashes of green and yellow insects in our gardens.

But in recent years Christmas beetle sightings appear to be dwindling. 

A new online study is hoping to recruit community scientists and budding entomologists to help track and count the beetles.

Tanya Latty, an entomologist from the School of Life and Environmental Science at the University of Sydney, said there had never been a dedicated long-term study in the decline of Christmas beetles.

“While everybody feels like numbers are going down and people claim that we don’t see them in the numbers that we used to, we don’t have that data,” she said.

“This is why we have launched the Christmas beetle count through the iNaturalist website in the hope of getting some good numbers on what is happening with Christmas beetles.”

Associate Professor Latty said the possible decline could be due to several factors including the increased use of broad-spectrum insecticides and pesticides in gardens.

“Applying any sort of curl grub killer or insecticides to the soil is generally not a good idea for any gardener,” she said.

“Most of those chemicals are broad-spectrum, which means they will affect a large range of insects and it also mucks up the soil ecosystem.”

Scientists believe other reasons for the decline could be habitat change, as a lot of the native bushland and grassland the beetles would spend time in as larvae have disappeared or been destroyed.

“Things like climate change can also mess around with when insects come out,” Associate Professor Latty said.

Chris Reid, a principal research scientist at the Australian Museum, said Christmas beetles were named after the time of year they appeared rather than their shiny colouring.

“Drought is probably a principal reason why we haven’t seen as many over the past few years. If the ground is too dry, the adults can’t emerge from the soil.

“There also changes in the urban environment and the expansion of urban areas.”

Associate Professor Latty said a big entomological study would traditionally take a lot of time and money with trained people outside collecting data.

“What’s changed is that websites like iNaturalist can harness the power of citizens and community members who can go out there and get the data and post it online for us,” she said.

“By contributing to this project, you will be helping determine whether they are declining and, if so, what might be causing that decline

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