Cockroaches are evolution personified, a new study published in Science suggests. Researchers at North Carolina State University have found that German cockroaches have rapidly evolved an aversion to sugar in order to avoid poison traps.

For a long time, the best way to lure cockroaches into poison traps was to add a little bit of corn syrup. But some years ago, researchers found that certain cockroaches were able to avoid the traps by ignoring the sweet bait, reports the Associated Press. After testing several theories, what they found is that the cockroaches had evolved an aversion to sugar, making it unpalatable to them.

Cockroaches have a peripheral gustatory system, which allows them to process certain stimuli like glucose, the researchers wrote. In wild-type cockroaches, exposure to glucose and fructose stimulates sugar-gustatory receptor neurons (GNRs), attracting the cockroaches to the source of the sweet. But in the evolved glucose-averse cockroaches, the team said, glucose stimulated both sugar-GNRs and bitter-GNRs, which in wild-type cockroaches are only stimulated in the presence of a deterrent like caffeine. The bitter-GNRs overwhelm the sugar-GNRs, and what was once a tasty treat turns into the cockroach equivalent of Brussels sprouts.

"Thus, D-glucose is processed as both a phagostimulant and deterrent in [glucose-averse] cockroaches, and this newly acquired peripheral taste sensitivity underlies glucose aversion in multiple [glucose-averse] populations," the team wrote. "The rapid emergence of this highly adaptive behavior underscores the plasticity of the sensory system to adapt to rapid environmental change."

North Carolina State entomologist Jules Silverman, a co-author on the new study, told AP that the evolved trait shows how highly adaptable cockroaches are to their environment. "They're doing pretty well in the arms race with us," he added.

Although it's unclear exactly when the cockroaches started to lose their taste for sugar, study co-author Coby Schal told AP that he estimates it took about five years, or about 25 generations, to spread to enough cockroaches that the baits were no longer effective.

The researchers focused only on the small German cockroach, not the large American cockroach, AP says. Other teams are now looking at whether different species of the roach exhibit the same adaptive aversion to sugar. While it doesn't explain why some cockroaches avoid traps without sugar bait in them, or why some populations of cockroaches have the new trait and others don't, the researchers hope that by learning how cockroaches evolve to survive in their environment, they may be able to find ways to create better baits and more effective poisons, AP adds.

Source: Wada-Katsumata A, Silverman J, Schal C. Changes in Taste Neurons Support the Emergence of an Adaptive Behavior in Cockroaches. Science. 2013.