How to kill cockroaches by offering them sexS

Researchers who synthesized an artificial sex pheromone have just discovered that it's most useful application so far is . . . killing cockroaches?

Female cockroaches, specifically the wood cockroach Parcoblatta lata, communicate their willingness to mate by releasing a hormone that can travel long distances to attract males. A research team from North Carolina State University suggested that a synthetic version of this pheromone (dubbed parcoblattalactone) could tempt roaches out into the open with the promise of sex.

Other than the satisfaction of tricking a cockroach, what's the point? This species of wood cockroach happens to make up over half of the diet of the endangered red-cockaded woodpecker. As the researchers explain in their paper: "Because reproduction in red cockaded woodpeckers is dramatically affected by seasonal and spatial changes in arthropod availability, monitoring P. lata populations could serve as a useful index of habitat suitability for woodpecker conservation and forest management efforts." In any given area, the number of puzzled cockroaches that respond to an odorous sexual invitation serve as a barometer for local woodpecker's prospects of survival.

Perhaps more relevant to human interests is the wood cockroaches' willingness to follow the parcoblattalactone anywhere. Although these are outdoor bugs, they are often drawn to house lights. A tempting scent might draw the roaches out of houses, and (hopefully) into the jaws of hungry birds.

For the NCSU researchers, identifying and recreating parcoblattalactone was a multi-step process. They started with a soup of hormones that cockroaches produce regularly, and ran it through a gas chromatograph. In this device, a gas made up of different chemicals is sent in a mobile stream of gas stream a tube with a stationary filling. Because the various chemicals in the sample travel at different rates through the filter, especially when the temperature is carefully maintained to control the flow, each chemical compound exits the tube at a different time. As each separated compound emerged from the tube, researchers ran it past a cockroach antenna while monitoring the antenna's electrical activity. The chemical that elicited extra sparks was identified as parcoblattalactone,

Once the chemical had been identified, researchers used a spectroscopy method called nuclear magnetic resonance to determine its exact composition. With this knowledge, they could synthesize a replica of the pheromone.

Surprisingly, when tested outdoors, the synthetic pheromone not only lured male P. lata into traps, but also snared males from several of the 11 other wood cockroach species. The fact that certain species share an attraction to the same sex pheromone compound indicates that they may be more closely related, on an evolutionary scale, than those wood roaches that were able to resist the signal. It also serves as a reminder that parcoblattalactone is only one component, albeit a major one, of a cockroach sex pheromone mix. Mixing other components of the pheromone blend with parcoblattalactone could help researchers draw all of the Parcoblatta species out of the woodwork.

Via Proceedings of the National Academy of Sciences.

Image by Bill Johnson on BugGuide.