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The natural History of the Cockroach, on this Moment of Science.

For certain species of cockroach, humans make the perfect roommates. Why do cockroaches like living in our houses? And what do they do when they’re not bugging us?

Although most us think of cockroaches as vermin, they do have a useful ecological role. Cockroaches are professional recyclers, chowing down just about anything, including dead plants and animals, and animal waste.

Their digestive systems are up to the task because they contain bacteria and protozoa that help convert the world’s waste into easily-absorbed nutrients. In the wild, the waste of roaches nourishes growing plants, continuing the cycle.

Day In The Sun

300 million years ago, the Carboniferous period was the cockroaches’ day in the sun so to speak. The whole earth was swampy and hot, with new plants and animals appearing on the scene, creating lots of waste for roaches to recycle. As the earth’s climate changed, becoming colder and dryer, cockroaches survived mainly in the tropics

A few hundred million years later, ships full of food and humans set out from the tropics, carrying clandestine cockroaches on board. Cockroaches disembarked in ports all over the world, searching for new homes. You might not have compared your house to a Carboniferous swamp, but the similarities wouldn’t escape a cockroach.

Cockroaches And Humans

There are lots of tasty crumbs littering the floor, a nice warm temperature year-round, and endless crannies to hide in. Despite these ideal living conditions, not all wandering cockroaches chose to shack up with humans. Of the 55 species of cockroach in the US, only 12 prefer human dwellings. The rest live outside, recycling without bugging us at all.