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Calling all cockroaches

An adult female German cockroach exhibiting "calling behavior" during which the female raises her wings and emits a volatile pheromone (blattellaquinone) from the last abdominal segment. [Image Science]
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Researchers have discovered a new way to trap cockroaches that could radically improve pest control. This is good news for anyone who doesn't like cockroaches and especially for those who are allergic to the insects.

Proteins from cockroaches, dust mites, mold and other substances can cause asthma and other allergic reactions, especially in kids and the elderly. In recent years, researchers have noticed that increasing numbers of children have been getting asthma. Part of the reason seems to be that kids are spending more time indoors, where these proteins, or "allergens," are floating around.

The best way to get rid of cockroaches is to detect them early and then spray with pesticides. But, these creatures live in dark nooks and crannies where it's difficult to see, and lots of roaches may have moved in before you spot one out in the open.

You can buy sticky glue traps to capture cockroaches as they prowl around in the dark, but these aren't very efficient, according to researcher Coby Schal of North Carolina State University. The new method will allow people to better detect and monitor cockroach populations, so they know when to spray with pesticide.

Schal has spent 15 years studying the lives of cockroaches, and his colleague, Wendell Roelofs of Cornell University calls him "Mr. Cockroach." In the 18 February issue of the journal Science, Schal, Roelofs, and their coauthors now describe their trick for trapping male cockroaches.

A group of adult male German cockroaches feeding on pig food in an infested pig farm. [Image Science]
Click here for a high resolution photograph.

What's the best way to attract male cockroaches? With the perfume of female cockroaches.

The female cockroach emits a compound called a "pheromone" into the air when she is ready to mate. She typically stands on a high surface like a countertop, raises her wings and releases the pheromone from a gland in her abdomen. The compound signals that the female is ready, and males show up moments later.

For the first time, the researchers have identified the pheromone from the German cockroach, which is one of the most common, persistent household pests worldwide.

The researchers purified the pheromone from cells taken from thousands of cockroaches. Based on what they learned from the purified pheromone, Schal and his colleagues were also able to create a synthetic version. To see if it worked as well as the natural version, the researchers added the synthetic pheromone to traps and placed them around a cockroach infested pig farm.

The traps were glass jars smeared with petroleum jelly on the inside to make them slippery, so cockroaches couldn't climb back out. After a while, the researchers discovered that the jars had attracted plenty of male roaches.

The researchers named the pheromone compound "blatellaquinone," since the German cockroach is also known as Blatella germanica.


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