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Missing Wings on an ‘Alien’ Beetle Pose an Evolutionary Mystery

The insect in the small specimen collection of Lund University in Sweden looked out of place.

“OK, this is a prank,” Vinicius Ferreira, an insect taxonomist and evolutionary biologist, said to himself. “It’s a joke.”

The beetle — only one-tenth of an inch and found in 1991 in Oaxaca, Mexico, among leaf litter of a pine and oak forest floor at an elevation of more than 9,500 feet by the naturalist Richard Baranowski — was most definitely a male. But it was missing one of the animal’s defining characteristics: the tough forewing casing known to scientists as the elytra.

After careful analysis, Dr. Ferreira described the insect this month in the Zoological Journal of the Linnean Society as a previously unknown but “extraordinary” elytra-less species of beetle: Xenomorphon baranowskii.

“Boom. We found this really weird animal. The ‘alien’ beetle,” Dr. Ferreira said, selecting a name that honored Dr. Baranwoski and also called to mind the “Alien” of his favorite sci-fi movie franchise.

“We finally found one. I think it’s very exciting,” said Michael Ivie, curator of entomology at Montana State University who was not involved in the research. “This is an amazing beast.”

“We can’t do a lot yet, but up until this discovery, we didn’t know there was something to even look for,” he added.

Wings consume a lot of energy, so throughout evolutionary history, many insect species have independently lost the ability to fly. But there are more than a half-million known beetle species, and until now, all have had at least some form of hard forewing elytra. Even in cases where it’s not used for flying and is fused together, this shell-like wing cover is thought to be one of the keys to beetle survival. It protects their soft body and lets them squeeze into small crevices and out of dangerous situations.

In the case of Dr. Ferreira’s alien beetle, he and his colleagues speculate that quitting flying and shedding the elytra could be a protective measure to avoid getting blown away by big gusts of wind at the high elevations where they live.

Dr. Ferreira also connected the species to a poorly understood evolutionary trend he and others have studied called paedomorphosis. In this phenomenon, adult females of some beetle species retain a few of their juvenile features, look more like larvae and sometimes even lose their wings. The winglessness of the male Xenomorphon baranowskii resembles what has been found in females of those beetle species.

But typically, male beetles use their power of flight to chase females far and wide for mating. So if paedomorphosis was already perplexing in female beetles, it makes even less sense that a male beetle would not develop wings as an adult. “It is the most extremist example of paedomorphosis,” Dr. Ferreira said.

“It’s not so good for you to be paedomorphic,” he added, as it leaves individual beetles more vulnerable to threats, and unable to get very far. But, his team hypothesizes, losing forewings and the ability to move could allow a beetle species to become more specialized and to more successfully occupy a tiny geographical niche.

These findings could serve as an example of how extremely adaptable beetles have been throughout their evolution — a trait that makes them one of the most successful animals on the planet. “This is an extreme situation,” said Robert Anderson, a researcher at the Canadian Museum of Nature who was not involved in this study. “This is obviously way out there in terms of its strangeness.”

The description is also based on a single specimen of Xenomorphon, and although entire species of insects are often described from one-off discoveries, researchers know virtually nothing else about the animal. Its DNA could not be studied, there are no data about its life history and there’s no trace of what females from this species might possibly look like. The next step would be to hike back up that Mexican mountain in the hopes of finding more elytra-less beetles.

“I honestly knew this would eventually come up someday,” Dr. Ferreira said. “It’s really puzzling, but everything is possible with beetles.”

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