If you’ve ever seen a cockroach scurrying across your kitchen floor or restaurant wall, chances are it’s a German cockroach. The German roach is the most common of the 70 different cockroach species in the United States.
For 250 years, scientists did not know where it came from or how it managed to spread to every continent on Earth except Antarctica. Now this mystery has been solved, and the answer is that it’s largely our fault.
The German cockroach is “a creation of human-made environments,” Edward Vargo, a professor of entomology at Texas A&M University and co-author of a new study identifying the cockroach’s origins, told the Washington Post.
The German cockroach cannot survive “temperate winters outdoors” and all cockroach species “prefer warm, humid places where they can feed on human and animal foods, decaying and fermenting matter, and a variety of other items,” according to the Illinois Department of Public Health.
Therefore, it is safe to say that if man-made establishments like homes, stores, restaurants, and other buildings did not exist, these harmful pests would not exist either.
The researchers published their results last week in the peer-reviewed journal Proceedings of the National Academy of Sciences.
Where does the German roach come from?
Scientists have long known that this species thrives indoors, but its origins remain a mystery.
Through DNA analysis, Vargo and his colleagues discovered that the species’ closest relative is the Asian cockroach.
The German roach evolved from its Asian cousin about 2,100 years ago to adapt to “human settlements in India or Myanmar,” the researchers reported in their paper.
Thanks to advances in transportation and “temperature-controlled housing,” the German cockroach has relatively recently spread around the world, the researchers said in their report.
How the German cockroach took over
The German cockroach’s adaptation to warm environments, its ability to reproduce quickly, and its unique resistance to insecticides make it a frustratingly common presence in households.
For example, over the course of her life, an adult female German roach can produce four to eight egg capsules containing up to 48 eggs each, according to the Penn State Department of Entomology. Do the math and that adds up to between 192 and 384 cockroaches, if each egg survives to adulthood.
But German cockroaches did not migrate thousands of miles across oceans and continents on their tiny insect-like legs. Their global spread coincides with advances in human movement and housing, according to the study.
In particular, the researchers determined that the spread of the German cockroach began along two routes, west and east of its origin in India or Myanmar.
The cockroach’s westward spread likely occurred at a time of increased “commercial and military activities of the Umayyad or Abbasid Islamic caliphates” around 1,200 years ago, the researchers reported. Meanwhile, the pest’s eastward spread around 390 years ago was likely caused by “European colonial trade activities between South Asia and Southeast Asia.”
Understanding the origins of German cockroaches could help other scientists understand how the species evolved to become so resistant to common insecticides. One study found that they are resistant to five types of common household insecticides.
“If we can know the origin of the species, we can try to identify the mechanism of this rapid evolution of insecticide resistance,” Qian Tang, a research associate at Harvard’s Rowland Institute who led the study, told the Post. new study.
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