The discovery of a fossil of two mating insects reveals that this particular bug, known as a froghopper, has been mating the same way for more than 165 million years.

"We found these two very rare copulating froghoppers which provide a glimpse of interesting insect behavior and important data to understand their mating position and genitalia orientation during the Middle Jurassic," researcher Dong Ren of the Capital Normal University said in a statement.

Uncovered in northeastern China, the fossil is the oldest such fossil ever uncovered, with the previous record holder belonging to two fly fishers caught in a 135-million-year-old embrace, The New York Times reports.

"This one is so rare," Chungkun Shih, a visiting professor at the university and one of the authors of the paper, told the Times. "I got involved in this research in 1999, and I have seen more than half a million fossils," but this, he said, was the only one that clearly depicted copulation.

The fossil portrays a belly-to-belly mating position, the male reproductive organ clearly inserted into the female copulatory structure.

"Obviously, there's behavior going on here," said Marlene Zuk, an evolutionary biologists at the University of Minnesota.

In addition to revealing that froghoppers have been mating the same way for millions of years, the fossil offers a look at the bugs' genatalia, which, apparently, have also remained the same.

When asked as to the reason behind such consistency, Shih says the answer is likely a simple one. "This works," he told the Times. "They don't need to change."

The study, entitled "Forever Love: The Hitherto Earliest Record of Copulating Insects from the Middle Jurassic of China," was published in the journal PLOS ONE.