By Tatsuo Nakajima
The Yomiuri Shimbun
WASHINGTON — The pest control industry may have to go back to the drawing board after a discovery by researchers at North Carolina State University revealed that some cockroaches have evolved to avoid sugary bait.
The researchers have found that certain populations of German cockroaches have mutated to taste sweet as "bitter" in a defense mechanism against poison traps.
The experts, which include chief researcher Ayako Wada-Katsumata, published their findings in the journal Science.
Many roach traps are laced with glucose, a common form of sugar, to attract cockroaches. However, such traps are believed to have become less effective over the past 20 years.
Cockroaches are able to "sample" their food before eating through "taste hairs" around their mouths. The insects' nerve cells respond differently depending on the taste, generally eating sweet foods and avoiding bitter ones.
The researchers studied the nerve cell responses of more than 7,000 cockroaches by feeding them substances such as glucose and salt. They observed that some cockroaches found glucose to taste bitter, while others were only able to taste sweet.
University of Tokyo Prof. Kazushige Tohara, an agro-bioscience expert, said this is the first confirmation of how quickly the insects' taste sensors can evolve, even to the point of changing their behavior.
"The research results are quite interesting in that it could help us discover how their sense of taste evolved according to their food and environment," he said.