One can safely assume that cockroaches are not among the typical urban resident’s favorite animals. While they are not as dangerous as, say, a malaria-carrying mosquito, or a tse-tse fly, they can potentially transport infectious agents, and have been implicated in some human allergies. Mostly, though, people just think that they’re gross. They’re also quite hardy, and able to go for fairly long periods without food or water; getting rid of them can be a chore.
Back in 1976, the Black Flag company introduced a roach trap called the Roach Motel™; it is a small enclosure, which contains a slow-acting poison mixed with a bait. (Other companies marketed similar products.) The idea is that roaches will be attracted to the bait, and then carry the accompanying poison back to their nests, thereby getting other roaches as well. The product was quite successful, in part because of aggressive advertising, and its memorable slogan, “Roaches check in, but they don’t check out.”
More recently, though, users have noticed that the traps were becoming less effective. The New Scientist has a recent article on some research that may explain why. One of the ingredients in the bait used is the simple sugar, glucose. It seems that the roaches have evolved a distaste for glucose.
In the race for world domination, cockroaches have scored another point against Homo sapiens. Their weapons? A distaste for sugar and a helping hand from evolution.
In a paper published in the journal Science, researchers at North Carolina State University in Raleigh discovered that some roaches of the species commonly known as “German cockroaches” [Blattella germanica] had a difference in their neurochemistry that caused glucose to “taste” bitter, a trait which they passed on to their offspring. The use of glucose as a bait in poisoned traps creates selection pressure that favors roaches without a sweet tooth. Hence, the authors suggest, evolution is at the heart of the traps’ decreased effectiveness.
This kind of evolutionary “arms race” is similar to what we have seen in the development of antibiotic-resistant bacteria, DEET-resistant mosquitoes, and herbicide-resistant weeds. We humans are quite good, in many cases, at devising ways to modify our environment. But we too often forget that our environment is not just a passive lump of matter — when we push, it frequently pushes back.