Christmas beetles can still be found in Brisbane gardens. But can you tell them apart?

Summer rains from early November have brought the return of the herald of the Australian holiday season: the Christmas beetle.

Many south-east Queensland locals remember the insects from their childhoods – recalling bigger populations than appear to be living in the region today.

While hard historical data is scarce, many insect species are in long-term decline, and experts say that “charismatic” species like Christmas beetles are what people notice.

But entomologist Dr Nicole Gunter says that following two wet summers on Australia’s east coast, sightings of Christmas beetles have recently increased.

“Not only is this year wet, but last year was wet, so it meant that if that whole last generation had really successful breeding, then [the young] would have had good odds at surviving,” she says.

“Many insects have larger numbers of offspring than, for example, some vertebrates, so that ability to bounce back when the conditions are right is very, very promising.”

That means you might be more likely to come across a beetle in your backyard this year. So what exactly makes a beetle a Christmas beetle?

Gunter is a curator at the Queensland Museum at Kurilpa, which houses between 4000 and 5000 Christmas beetle specimens in its entomology collection.

“What we think of as Christmas beetles here in mainland Australia, particularly on the east coast, are a group of scarab beetles in the subfamily Rutelinae,” she says.

There are over 35 species of these mainland Christmas beetles, all of which are Australian natives and feed primarily on gum tree leaves as adults.

Christmas beetles common in the south-east, from left: Anoplognathus porosus, Anoplognathus boisduvalii, Anoplognathus pallidicollus, Anoplognathus concolor.Credit: Catherine Strohfeldt

“In south-east Queensland there are about 10 or so species depending on exactly where you are [and] there’s about three to five relatively common ones,” said Gunter.

“The one that is most common in Brisbane is Anoplognathus porosus. I believe the common name of that is the washer woman.”

Other common species included the campfire beetle (Anoplognathus concolor), the cashew beetle (Anoplognathus pallidicollus), and Anoplognathus boisduvalii – a striped variant.

Adult Christmas beetles live in dry bushland and rainforest, emerging from pupation in the wet summer months, around Christmas. For the rest of the year, the beetles live underground as grubs, feeding on decaying plant matter and nibbling roots.

Location dictates colour variation, with many brighter Christmas beetle species calling North Queensland’s wet tropics home, although pattern, size and colour vary beetle to beetle.

With beetles being the most abundant type of animal in the world – making up 20 per cent of all species – Gunter said the legs and claws were the best measure to tell Christmas beetles apart.

“If you look at [Christmas beetles’] legs, they’re often wider than those cane types [and] you’ll see that instead of the claws being nice and close together they’re asymmetrical,” she said.

Christmas beetles have notably thicker legs than other beetle species. From left: an Argentinian scarab beetle, a cane beetle species, and a Christmas beetle.Credit: Catherine Strohfeldt

“I would recommend if someone wants to identify a beetle, take a picture from the top, flip it over, take one from the bottom, take a good photo of its face, one in its head … [and a] posterior photo.”

The hair on the rear abdomens of these beetles – pallidicollus (left) and boisduvalii (right) – can help you tell them apart.Credit: Catherine Strohfeldt

Finding a definitive answer as to what species you’re looking at is difficult, Gunter added, “unless you’re a beetle specialist”.

Backyard enthusiasts without a science degree can instead use the Australian Museum’s Christmas beetle ID app – and contribute to a citizen science project that tracks Christmas beetle populations as they fluctuate from year to year.

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