Are Christmas beetles in decline? Help find out with citizen science

In southern and eastern Australia, summer is heralded by the arrival of swarms of colourful Christmas beetles.

The iridescent insects are not only a pretty addition to the bush and suburbs: when they’re most active in December and January, they provide a valuable food source for birds, possums and wasps.

But it seems that the beetles may be in decline. A citizen science project led by University of Sydney researchers and not-for-profit, Invertebrates Australia, is seeking to find out.

“There’s around 35 different species of insect that we call Christmas beetles,” explains Associate Professor Tanya Latty, an entomologist at the University of Sydney. “They all belong to one genus called Anoplognathus.”

The researchers suspect the beetles’ populations are dropping, based on anecdotal evidence, and loss of their preferred woodland habitat across Australia.

“There are reports from the early 1900s of there being so many Christmas beetles that trees would bend over,” says Latty. “You just don’t see that anymore.”

But without consistent data, it’s hard to tell: especially for creatures that exist as larvae in the soil for most of the year, only hatching and flying about for a few months.

“There’s no long-term monitoring of Christmas beetle populations,” says Latty.

“We certainly expect, with insects, that sometimes you’ll have years where there are many and sometimes you have years where there are few. What we’re worried about is that over decades, it seems the overall numbers are going down, even if we do get these peaks here and there.

“The other problem is because there are so many different species, we don’t know if some species are doing fine and others are doing very badly. The worry is that there may be some species that have quietly disappeared.”

The researchers are hoping, through the Christmas Beetle Count, that members of the public can help them establish some clearer beetle data.

Citizen scientists can photograph beetles, and then log this with the iNaturalist website or app.

“What we really need is for everyone to be our eyes on the ground and get that data for us, so that we can start thinking about where the problem areas are, and then start thinking about what we can do about it,” says Latty.

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Excited in more than just Christmas beetles? Here are some more citizen science projects to join.

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While long term trends will (by definition) take years to see, Latty hopes that a year or two of citizen data will be enough to see which locations need more investigation by scientists.

If you’re interested in helping you can download the iNaturalist app (or just use the website) and keep your eyes peeled for beetles.

“They’re nocturnal fliers, so you’ll see them more likely at night around street lights or porch lights,” says Latty.

“If you have a porch light on, just go outside and have a look around – if you see something big bumping into it and you can get a picture of it, that would be awesome.

“The adults feed on eucalyptus leaves – so if you’re out in the bush, look up into the trees. Sometimes you can see thousands of Christmas beetles munching away.”

Try and get a photo of the top, bottom, back and rear of the beetle for the best shot at identifying it.

“The phone app will try to identify the thing you’ve taken a picture of, so don’t worry about whether it’s a Christmas beetle or something else – the computer will handle that. Then, we manually go through and check.”