Next time you're faced with a serious bug infestation, you might try spraying your house with eau-de-death.

Scientists have discovered that insects from cockroaches to caterpillars all emit the same stinky blend of fatty acids when they die, and this sinister stench sends bugs of all kinds running for their lives.

Biologist David Rollo of McMaster University in Canada made this morbid discovery while studying the social behavior of cockroaches. When a roach locates a great new abode (like your kitchen cupboard), it gives off a chemical signal to attract its cockroach friends. To determine the chemical composition of these pheromones, Rollo and his team started crushing dead cockroaches and spreading around their body juice.

"It was amazing to find that the cockroaches avoided places treated with these extracts like the plague," Rollo said in a press release. "Naturally, we wanted to identify what chemical was making them all go away."

Of course, there was nothing to do but grind up more bugs. The team found that their concoction repelled not just cockroaches, but ants, catepillars, woodlice and pillbugs. And even though they're technically crustaceans rather than insects, dead woodlice and pill bugs produced the same set of fatty acids as the other animals.

Insects and crustaceans diverged from each other 400 million years ago, so the researchers think their death mix represents a universal, ancient warning signal. "Recognizing and avoiding the dead could reduce the chances of catching the disease," Rollo said in the release, "or allow you to get away with just enough exposure to activate your immunity." The researchers published their findings in this month's edition of Evolutionary Biology.

The scientists hope the right concoction of death smells might protect crops against pesky invaders. For instance, a log treated with the fatty acids repelled wood beetles in a forest for a full month.

Thankfully, human noses can't detect the fatty acid extracts. "Not like the rotting of corpses that occurs later and is detectable from great distances," Rollo wrote in an e-mail. "I've tried smelling papers treated with them and don't smell anything strong and certainly not repellent."

Image: Flickr/bensheldon. Note: This photo was chosen from a disturbingly large volume of dead cockroach images on Flickr.

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