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Cockroaches Have Evolved to Avoid Our Traps

In just a few years, cockroaches evolved to avoid our poisons

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German cockroach. Photo: David Minniaux

When cockroaches were discovered scuttling around in the blast zone from the nuclear bombing of Hiroshima and Nagasaki near the end of World War II, it invigorated the myth that these creepy crawlies could survive anything. And the idea that roaches will survive til the end of time just got a boost: Scientists discovered that some of the little buggers have evolved to outwit our poison roach traps.

In the 1980s a new type of roach trap was introduced: a sugary snack laced with poison. But after just a few years, a blink of an eye on evolutionary timescales, some roaches evolved to resist the traps.  Scientists “realized that some roaches had developed an aversion to glucose—the sugary bait disguising the poison—and that the insects were passing that trait on to their young,”  says Science Magazine.

Though scientists knew that roaches were growing to avoid the traps, they weren’t sure what, exactly, was causing the change. In a new study, researchers report that, more than just learning that traps mean death, the selection pressure of the poisoned sugar actually bred a race of roaches for whom one type of sugar—glucose—tastes bitter. To avoid certain death, the roaches evolved to rework their sense of taste.

To test the roaches’ taste, says the BBC, scientists gave the roaches jelly, a food full of glucose.

“You can see the mutant cockroaches taste the jelly and jump back – they’re repulsed and they swarm over the peanut butter.

…Highly magnified footage of these experiments clearly shows a glucose-averse cockroach reacting to a dose of the sugar.

“It behaves like a baby that rejects spinach,” explained Dr Schal.

“It shakes its head and refuses to imbibe that liquid, at the end, you can see the on the side of the head of the cockroach that has refused it.”

According to Science Magazine, though evolving to avoid glucose helps the roaches avoid our poisoned traps, it also hurts them in other ways—glucose is full of energy, and glucose-averse cockroaches grow more slowly than their less picky brethren.

More from Smithsonian.com:

Cardboard Cockroach Is the Fastest, Creepiest Robot in the World
Why Cockroaches Meticulously Groom Their Antennae

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About Colin Schultz
Colin Schultz

Colin Schultz is a freelance science writer and editor based in Toronto, Canada. He blogs for Smart News and contributes to the American Geophysical Union. He has a B.Sc. in physical science and philosophy, and a M.A. in journalism.

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