Researchers Find Two Fornicating Flies Enshrined in 41-Million-Year-Old Amber

Some 41 million years ago, a pair of flies locked in a tender tryst was interrupted by a falling glob of tree resin. Frozen in place by the fast-hardening goo, the two insects quickly suffocated to death—perfectly preserving the amorous act in fossil form.

Described in a paper published last week in the journal Scientific Reports, this raunchy piece of amber represents just one of a treasure trove of nearly 6,000 insect- and arachnid-laden fossils recently unearthed in Australia and New Zealand, reports Lucas Joel for the New York Times.

The finds mark one of only a few instances in which amber has been located in the land down under, making them, perhaps, “one of the biggest discoveries in Australian palaeontology,” study author Jeffrey Stilwell of Monash University tells Australia’s ABC News.

Among the entombed are spiders, mites and bits of plants and microbes, as well as the region’s oldest known fossil ants, reports Mindy Weisberger at Live Science. In all, the creatures within range in age from about 40 million years old to 230 million years old, during the late Triassic, when Australia still compromised the southern part of the supercontinent Pangaea. These dates make the team’s oldest fossils the most ancient bits of amber known from the region.

But the 41-million-year-old flies caught mid-copulation are perhaps the stars of the show. By this point in the planet’s evolution, Australia and Antarctica, which were then part of a landmass called Gondwana, had split off from their Pangaea parent. The pair belong to the Dolichopodidae family of long-legged flies, a group whose members are still around today—suggesting that many insect groups had already diversified, Ken Walker, an entomologist at the Museum of Victoria who wasn’t involved in the study, tells ABC News.

The flies’ risqué positioning also makes them unique. Amorous acts in freeze-frame are especially rare, as they require a near-instantaneous death to preserve them.

“I looked at the piece under the microscope, and when I looked at it, I said, ‘This looks really important, because it looks like they’re almost attached or something,’” Stilwell told the New York Times. “I couldn’t believe it—it looks like they’re mating.”

Victoria McCoy, a paleontologist at the University of Wisconsin, Milwaukee who was not involved in the study, points out an alternative scenario: The flies’ final positioning might not be a perfect replica of how they were intertwined in life. “It’s possible one fly was trapped in the amber and the other was a little excited and tried to mate,” she says.

Still, the fossil probably represents “true and valid information” about the bugs’ mating behavior, McCoy says. Whether brought on by death or passion, these lusty, leggy flies were certainly in the throes of something.

Katherine J. Wu | | READ MORE

Katherine J. Wu is a Boston-based science journalist and Story Collider senior producer whose work has appeared in National Geographic, Undark magazine, Popular Science and more. She holds a Ph.D. in Microbiology and Immunobiology from Harvard University, and was Smithsonian magazine's 2018 AAAS Mass Media Fellow.