“As to how this will affect the population, it’s really complicated,” said Dr. Wada-Katsumata.
That’s because, despite the hang-ups, glucose-averse cockroaches still find ways to do the deed.
In lab experiments, Dr. Wada-Katsumata and her colleagues showed that glucose-averse females are more skittish of males than wild-type cockroaches, which is what the researchers call the roaches without glucose aversion. However, they also found that glucose-averse males seem to compensate for this by more rapidly transitioning into sex after offering his gift.
“The glucose-averse females might spend, say, three seconds feeding on the male’s secretion,” said Coby Schal, distinguished professor of entomology at North Carolina State and an author of the study. “The wild-type male does not respond in three seconds. The glucose-averse male does.”
The researchers even have evidence that suggests that all of these new pressures are causing changes in the chemistry of the glucose-averse male’s nuptial gift potentially so he can continue attracting females.
From a scientific perspective, the German cockroach’s sugar saga shows how humans can drive both natural selection — the cockroaches that survive our poison traps — as well as sexual selection — the glucose-averse cockroaches who no longer want to mate with cockroaches that still offer sweet snacks.
“I think that’s what makes this so compelling,” Dr. Schal said. “The idea that humans impose very strong selection on animals around us, especially inside our home, and that the animals respond not only with physiological changes, but also with behavioral changes.”
The good news for consumers is that pesticide manufacturers share Dr. Wada-Katsumata and Dr. Schal’s enthusiasm for understanding cockroach evolution, and they are actively changing their cockroach-killing formulations to move away from glucose. But given how new this research is, it will take some time for those changes to make their way to the products on our shelves.
“The worst thing that you can have as a product is a bait that is not eaten by cockroaches,” said Dr. Schal.