Four species of cockroach that have never before been known to inhabit North America were reported to have been discovered by researchers from Slovakia, Russia, and the United States in the Jan. 5, 2014, edition of the journal Annals of the Entomological Society of America.
The oldest fossil dates to 49 million years ago. The insects were all found in the Green River Formation near Rifle, Colorado by David Kohls. Kohls is responsible for finding the majority of insect and plant fossils that have been found in the Green River Formation and was honored with the species name of the oldest of the new fossil cockroaches that he discovered.
All of the new fossil species of cockroach have been found in amber and sedimentary fossils in Europe and Russia but the oldest example is only 44 million years old.
The new discovery of one particular cockroach (Ectobius kohlsi) indicates that the species originated in North America instead of Europe. The species probably died out in North America due to cold temperatures that may have produced a loss of food sources. The same species has reentered North America in modern times as an invasive species from Europe.
The researchers compared the anatomy and vein structure of the wings of the ancient cockroaches found in Colorado with existing fossil cockroaches and determined that each of the newly discovered fossils is a species of cockroach that has never been seen before in North America.