The topic of the Common Rhinoceros Beetle (Xylotrupes ulysses australicus) came up over dinner with friends recently. I’m not sure how the conversation started but I was soon telling tales of growing up in Townsville where there always seemed to be plenty of them about. My brother and I used to collect them and encourage them to ‘fight’. I know – weren’t we awful?! Their tell-tale hissing and heavy, shining black armour reminded us of Darth Vader, and we thought that was great.
Having provided such happy childhood memories (I don’t think there was ever any serious damage done), I got a little nostalgic about these beautiful beetles, renowned for their large size and prehistoric appearance, and realised I hadn’t seen any for what seemed years. Then I saw one the very next day (or its head at least), and then two days after that (this time it was just the body – I don’t think they belonged to the same animal). Maybe I hadn’t noticed them of late simply because I hadn’t been looking for them. After all, it doesn’t seem appropriate to conduct beetle warfare in the office lunchroom, particularly given the environmental inclination of my colleagues. With a little research though, I realised the other likely reason for seeing them comparatively less frequently around Brisbane and the coast is because down here, they only come out in summer. In North Queensland, they’re about all year round.
In Southeast Queensland they come out in summer because it’s the season in which they mate, from late December to the end of January or even early February. They’re attracted to bright lights so can sometimes be found congregating below street lights. Males can also be seen in large gatherings on the trunks and branches of trees, particularly Poinciana trees (Delonix regia) where they enter into what is thought to be a pre-mating ritual, knocking other males off the branch over the scent of a female’s pheromones. It’s their horns which give them the means and strength to do this, not to mention their name. The males have a double-pointed, curved horn on their head and a heavier one on the front part of their thoraxes. Relative to its body weight, this insect is considered to be the world’s strongest animal. Females are less notable; they lack horns, are smaller and are seen less frequently.
Having mated, the female lays approximately 50 white eggs in rotting wood and organic matter where they take three weeks to hatch. Once they have emerged, the larvae live in and feed on organic material for approximately two years as they grow to full size. As I remember the larvae were common residents of our compost bin. They’re enormous, and can reach the size of an adult’s palm. Like all other members of the Superfamily Scarabaeoidea (commonly known as scarab beetles), the larvae are termed ‘curl grubs’ because they curve in a half circle. At full size the larvae make a cell in the soil, recycling their faecal matter to provide a waterproof barrier. One month on, they emerge as an adult, which lives for only 2-4 months.
As adults their diet is somewhat more varied and can include the bark of young shoots, sap, rotting fruit, carrion and dung. They’re able to detect strong-smelling food from some distance away and can triangulate its direction by spreading their antennae, which have flattened ‘leaves’ attached to the end of each stalk. The inside of these leaves are covered with minute smelling organs which, when opened like a fan, can detect strong-smelling food from far away. These antennae are typical of all scarab beetles and can be folded flat when the beetles are burrowing, to protect their delicate sensory organs.
The Common Rhinocerous Beetle isn’t the only rhinocerous beetle living in Southeast Queensland. Haploscapanes australicus is rare but can be distinguished by its two short horns on the thorax, as opposed to Xylotrupes ulysses australicus, which has just one. Across Australia there are nearly 200 species of rhinoceros beetle, most of them smaller in size but just as impressive in structure. Unfortunately there is one intruder who has infiltrated its way into the Australian group; the African Black Beetle (Heteronychus arator) is about 15mm long, has no horns and is a serious pest of lawns and pastures in New South Wales and Queensland.
As for that hissing noise they make when disturbed, well it turns out that it’s not Darth Vader reincarnated but, in fact, the sound of one part of their abdomen rubbing against the ends of their forewings (elytra). Unfortunately for them, their bark is certainly worse than their bite though and whilst their hissing squeaks are meant to act as a warning to enemies, they’re actually incapable of defending themselves against serious attackers.
Article by Lexie Webster
Land for Wildlife Officer
City of Gold Coast