Why The Australian Jewel Beetle Love Beer Bottles

May 24, 2023 0 comments

The Australian jewel beetle (Julodimorpha bakewelli) is a large golden-colored beetle species that is found all over South Australia in arid and semi-arid areas. Like most insects, the jewel beetle’s only purpose in life is to breed. Every year during mating season, the males fly around, searching for the shiny brown backs of the females crawling on the ground. When they find a lady they like, they hop on her back and start humping—except, many times, the mate of their choice turns out to be something else.

Several Australian jewel beetles trying to mate with a beer bottle. Credit: National Geographic

Back in the spring of 1981, which occurs in August and September in Australia, two entomologists, Darryl Gwynne from the University of Toronto in Canada and David Rentz from the CSIRO, were on a field trip in Western Australia where they made a remarkable discovery. The pair observed several male Australian jewel beetles trying to mate with a 375ml beer bottle, known affectionately as a ‘stubbie’. They picked up the bottle and tried to shake off the beetles, but the insects had gripped the bottle fiercely and wouldn’t buzz.

Looking around, the researchers found more stubbies, and each one was mounted upon by several males. The males had their genitalia everted as they attempted to mate with the bottle. The behavior perplexed Gwynne and Rentz, and so they conducted a brief experiment at the site. They found four empty stubbies and placed them on the ground. The area was littered with beer bottles tossed from open windows of speeding cars, so they had no trouble finding them. They wanted to see if the bottles would attract beetles. Sure enough, within half an hour, two of the bottles had attracted a total of six males.

What was drawing the beetles to the empty stubbies? Surely, it was not the beer, because the beetles didn’t go for the spout end, but rather the bottom. Also the bottles were long dry.

The answer became obvious when they took a closer look at the bottles, which was shiny brown in color with a ring of dimples near the bottom, similar to the tiny bumps on the beetles’ elytra. Apparently, the males were confusing the beer bottles for females of their species from the way the light reflected off their backs. Biologists call this "an evolutionary trap." It happens when environmental changes caused by human activities lead animals to make poor habitat choices that can lead to rapid population declines and even extinction. For instance, when sea turtle hatchlings emerge from their sandy nests, they instinctively migrate towards the moonlight reflecting on the ocean. However, the presence of bright lights from beach hotels can confuse the hatchlings, causing them to migrate in the wrong direction. As a consequence, they either succumb to exhaustion or become vulnerable to predation.

A male Australian jewel beetle attempts to make love with a beer bottle. Credit: Darryl Gwynne

Likewise, the Australian jewel beetles exhibit a similar effect. Mistaking beer bottles for females can have detrimental consequences for male beetles. Gwynne and Rentz documented how once the males landed on the bottles, they persistently attempted to mate with them until physically displaced. In their natural habitat, this behavior can lead to unintended starvation or exhaustion, ultimately resulting in their demise. The researchers observed instances where some males fell off the bottles due to heat exhaustion, while others became prey for predators such as ants.

Thankfully, Australian beer companies have changed the design on their beer bottles. It no longer has the little bumps that has been confusing the beetles.

Darryl Gwynne and David Rentz’s, who wrote a paper on this observation, won the 2011 Ig Nobel prize—a parody prize awarded annually by the scientific humor magazine Annals of Improbable Research, putting into spotlight this unusual aspect of the Australian jewel beetle.

# The Love That Dared Not Speak Its Name, Of A Beetle For A Beer Bottle, NPR
# Australia’s beer-loving jewel beetle, Australian Geographic


More on Amusing Planet


{{posts[0].date}} {{posts[0].commentsNum}} {{messages_comments}}


{{posts[1].date}} {{posts[1].commentsNum}} {{messages_comments}}


{{posts[2].date}} {{posts[2].commentsNum}} {{messages_comments}}


{{posts[3].date}} {{posts[3].commentsNum}} {{messages_comments}}