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Cockroach fossil shows American source for European bug

You’re welcome, Europe.

The most common genus of cockroach in modern Europe, Ectobius, likely spread from North America some 50 million years ago, according to a new fossil find described Friday in the Annals of the Entomological Society of America.

When scientists in the Baltic region discovered species of Ectobius preserved in amber, they assumed these insects had a purely Eurasian lineage.

But the discovery of four ancient species of Ectobius in the hardened sediments of ancient lake basins in the U.S. intermountain West has uprooted that belief. Those formations along the Green River in Colorado are at least 5 million years older than the Baltic samples, according to the report.

Ectobius has since reappeared in North America in modern times, a phenomenon that likewise occurred with the common horse. Equus, a genus that includes horses and zebras, first arose in the Americas and spread through Eurasia and Africa, only to become extinct in its home turf. Spaniards brought the domesticated horse back to North America in the 15th century.

In the last six decades or so, entomologists have described four Ectobius cockroach species that have reappeared in North America. Entomologists first identified samples of Ectobius lapponicus, describing it as a European “dusky cockroach,” in leaf litter around a house in New Hampshire in 1984. The species since has been found through the Northeast. Ectobius lucidus was first described in North America four years ago, when it was characterized as a European interloper.

"It was always assumed that these four newcomers were the first Ectobius species to have ever lived in North America,” author Conrad Labandeira, curator of paleoentomology at the Smithsonian Institution's National Museum of Natural History, said in a written statement. “But the discovery in Colorado proves that their relatives were here nearly 50 million years ago."

Why Ectobius apparently vanished from North America in the Eocene epoch is unknown. But Earth's climate was warmer then, and the European Ectobius species that thrive again in North America are more cold-adapted than their ancestors likely were, the authors noted.


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