Talk about getting caught in the act: Scientists say a fossil recovered in northeastern China depicts two insects locked in sexual congress roughly 165 million years ago -- the oldest such relic ever discovered.
In a paper published online Wednesday in the journal PLOS ONE, paleo entomologists described the amorous bugs as an extinct species of froghopper that exhibited striking similarities to their modern-day relatives.
Most remarkable, scientists said, was the fact that today's froghoppers mate in the same fashion their fossilized forebears did in the Middle Jurassic period: Belly to belly, or side by side.
"Froghoppers' genitalic symmetry and mating position have remained static for 165 million years," concluded lead author Shu Li, of Capital Normal University in Beijing, and her colleagues.
Fossil records of mating insects are rare. To date, fewer than three dozen known relics exist of copulating fireflies, mosquitoes, bees, ants, water striders and other bugs. Most are preserved in amber, researchers said.
Froghoppers are so named because they jump around on shrubs and other plants like tiny frogs. Froghopper nymphs are often called "spittlebugs" because they cover themselves with foaming spittle to protect themselves from predators, parasites or dehydration, authors wrote.
The insect fossil was recovered in Daohugou Village, within the Inner Mongolia Autonomous Region. The pair exhibited belly-to-belly mating position, with the male's aedeagus inserted into the female's bursa copulatrix, authors wrote.
The bugs measured just longer than 1½ inches.
Researchers said it was possible that the bugs were positioned side by side while mating and were displaced slightly as they were buried and slowly fossilized.
Researchers classified the pair as Anthoscytina perpetua. The name, they said, was derived from the Latin perpet, or eternal love.
"In reference to their everlasting copulation," authors said.