Christmas beetles: Facts and basic info

While December is often a time of chilly temperatures and dormant nature in the Northern hemisphere, it can be the heat of summer down under. In Australia, the years-end holidays are a much more exciting time for naturalists, with insects and migratory birds on the scene. While insects in Europe, Asia, and North America are hidden away from the cold, a group of gorgeous beetles are putting on a gorgeous show in Australia. For this Wildlife Spotlight post, let’s get to know Christmas beetles, Australia’s beautiful yuletide insects.

Read more: Where do bugs go in the winter?

What are Christmas beetles?

Christmas beetles are colorful, plant-eating beetles in the genus Anoplognathus. The 36 beetle species in this group live mostly in Eastern Australia, where they feed on eucalyptus trees and show up in parks and gardens during their mating season. Like platypus, kangaroos, and bilbies, this group of neat-looking beetles is found only in Australia, making them a local specialty down under. Unlike their mammalian neighbors, Christmas beetles don’t get a great deal of press despite their cool natural history.

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Christmas beetles may look familiar to readers from outside Australia, however. This is because they are members of the widespread scarab family (Scarabidae), a huge group found all over the world. Some of their close cousins include the Japanese beetle (Popilia japonica), an invasive species in North America and Europe, and junebugs (Phyllophaga sp.).

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These beetles can get relatively large (around 0.8 – 1.2 inches or 20-30mm in length), and often sport an iridescent sheen. While many species are brown or tan, some of the more flamboyant members of this group are golden, green and red, or even purple! These are chunky, rather slow-moving beetles that are somewhat clumsy fliers. Despite their large size, Christmas beetles are harmless to people and pets.

Why are they called Christmas beetles?

Christmas beetles get their name from their annual appearance, sometimes in large numbers, from November to February. Since Christmas falls right in the middle of this range, many people associate the appearance of these beetles with the holidays. Like many other insects, Christmas beetles are attracted to bright lights when flying at night, and can be attracted to displays like Christmas lights. This can’t hurt their reputation as diehard Christmas fans, either!

Why do Christmas beetles come out in the Winter?

One question that many nature lovers in other parts of the world ask about Christmas beetles is why adults emerge to feed and mate during the Winter. Importantly, since Australia is in the Southern hemisphere, the months of November through February are actually summer months. That is, they are some of the hottest months of the year, and also when rains may be typical. This creates ideal conditions for adult beetles to emerge and look for both food and a mate.

Life cycle

Like many other plant-eating scarabs, these critters begin life underground as a larva or grub. Christmas beetles typically lay their eggs into the soil in open, grassy habitats, where their grubs can find adequate food. The grubs then spend several months or a year or more feeding on plant roots, typically those of grasses. This diet allows them to grow large and molt as they mature. Once they reach an adequate size, the grubs pupate and develop into an adult beetle.

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The length of this underground growing phase depends on how quickly the young larva grows. In warmer areas or those with abundant food, the larvae grow more quickly and take less time to emerge as adults, probably less than a year. In colder, drier, or more food-scarce places, they may spend more than a year underground.

Once the larva has grown large enough on its diet of plant roots and pupated, it emerges during the warmest season, especially after rains. Rainfall makes the soil softer and easier for the young beetle to crawl through, and probably bodes well for abundant, leafy food on the surface. Adult beetles emerge during the Northern Winter months (November – February), and spend their time finding mates and munching on Eucalyptus leaves.

These adults spend more time feeding on leaves high in trees, and because of that they are found more often in forests, parklands, and back yards with abundant tree-cover. Once feeding and mating have been achieved, the cycle can start over again as females seek out open, grassy areas to lay eggs.

This use of open areas and grasslands as larvae, and trees and forested areas as adults, is what scientists and naturalists call habitat supplementation, where a species uses multiple habitat types to live its life cycle. As species that use habitat supplementation, Christmas beetles benefit from ecotones, or areas where two ecosystem types border one another. These areas give the beetles easy access both to feeding and egg-laying habitats.

Are Christmas beetles endangered?

A common theme in social media posts and news articles about Christmas beetles is concern over their declining numbers. Scientists and members of the public ask, “where have all the Christmas beetles gone?” While experts are quick to point out that we don’t have concrete data pointing to shrinking Christmas beetle populations, the anecdotal (or informal) observations are telling. People are seeing fewer of these cool insects each year in urban areas where they used to be common. Over the long term, this could be a very bad sign for Christmas beetles, implying their local or total extinction in areas where they once occurred.

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To address this problem, researchers at the Australian Museum, CSIRO, and local universities have begun a collaborative study to keep track of Christmas beetle populations. They created a mobile app that helps people identify Christmas beetles and even distinguish between species in their neighborhood. Using this app and iNaturalist, volunteers can submit their sightings and help scientists keep better track of Christmas beetle populations. With enough sightings over time, researchers will be able to get a handle on whether these beetles are indeed disappearing. Importantly, this project will also point the way toward effective conservation measures to protect these iconic animals. You can read more about the project here.

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Why might Christmas beetles be disappearing? Researchers’ first suggestion is the growing development of rural areas around Eastern Australia’s major cities. As more and more land, particularly woodlands and grassy clearings, are developed to provide housing for Australia’s growing population, less land is left over for the beetles. Because, as we learned above, Christmas beetles have specific habitat requirements to meet both their adult and larval needs, this development can be especially harmful.

Sources and further reading

Want to learn more about Christmas beetles? Check out the links below for articles that supported my learning for this post, and helpful books for a deeper dive.

Australian Museum, 2024. How to identify a Christmas Beetle.

The University of Sydney. Christmas Beetle count project

iNaturalist.org Christmas beetles (Genus Anoplognathus).

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