How the German cockroach made its way to Hawaii

Scientists analyzed the travel patterns of the German cockroach (Blattella germanica) to uncover why, and how, the species is found in locations from Hawaii to the North Pole.

Photo: Mark Sheperdigian

To answer their questions, scientists considered the DNA of almost 300 German cockroaches from 51 sites, including Hawaii.

Their research showed the cockroach had an Asian ancestor over 2,000 years ago, suggesting the pest moved throughout the world by attaching to another species: people. The ancestor, the Asian cockroach, resides in south Asia.

The German cockroach and the Asian cockroach most likely became two separate species about 2,000 years ago when the German cockroach adapted to be able to live in household conditions. Initially a disadvantage, the cockroaches’ inability to tolerate colder temperatures makes them a constant invader of indoor life.

While the German cockroach arrived in Europe roughly 270 years ago, arriving through Asia, the Hawaiian population of the species most likely travelled from the continental United States.

The German cockroaches found on the mainland in the U.S. are exactly the same as the ones found in Hawaii, according to Dr. Qian Tang, a postdoctoral researcher at Harvard University. Tang published his research about the origins of the German cockroach in the scientific journal the Proceedings of the National Academy of Sciences

Tang hypothesizes commercial or passenger ships brought the German cockroach from the mainland to the Hawaiian islands, ruling out that the pests came from other nearby continents like Australia.

Tang said populations of the cockroach are more closely related, no matter geographic proximity, when the two locations have frequent commercial connections.