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Last Updated: Friday, 18 February, 2005, 11:45 GMT
Sex hungry roaches lured to death
Cockroaches, Science
The German cockroach was a tough nut to crack
Synthetic sex pheromones are being developed as an ingenious way of luring randy cockroaches to their deaths.

For years, scientists have been trying to identify the special chemical emitted by female German cockroaches that brings males running from afar.

Now they have, Science magazine reports, and they hope to develop a special trap using the pheromone.

The trap would contain a lethal pathogen, which sex-hungry males would pick up and pass through their colony.

"We hope we will be able to attract them to traps which contain micro-organisms that will kill them eventually," said Wendell Roelofs, of Cornell University, New York, US.

"And cockroaches are very gregarious so they will run back and interact with other members of the colony and they'll pass the pathogen on to them."

Tough nut

The idea of using sex pheromones to catch pests is not a new one. It is all very well having an insect trap, but you need an effective bait.

Sex pheromones, emitted by most female animals when they are ready to mate, are something that their male counterparts find irresistible.

Scientists managed to identify and manufacture sex pheromones specific to certain species of cockroach some time ago.

But the most menacing of them all - the German cockroach - remained a tough nut to crack.

"The German cockroach is the biggest pest worldwide," said Dr Roelofs. "So people were looking way back in the 70s to see if they could synthesise it - but it eluded their attempts."

The problem was nobody could find where the pheromones were being emitted from.

After a long hunt, Dr Roelofs and his team found the relevant gland, right at the tip of the female cockroach's abdomen.

Male antenna

Their next task was to identify the particular chemical that drives males wild.

They did this by testing a series of possible candidates on a disembodied male antenna.

"The male antenna is the only detector in the world that can tell us which is the active compound," explained Dr Roelofs.

Cockroaches, Science
The German cockroach is the biggest pest worldwide
"We would strap the antenna between two electrodes, and the electrodes would record depolarisation in the antenna as soon as it was stimulated by the active compound."

Once the hapless antenna had led them to the right chemical, the team was able to manufacture it artificially. Now all they need to do is design a clever trap.

Dr Roelofs is aware that any swift-death trap will only eliminate males, since the chemical does not appeal to females.

So that is why he thought of the slower, deadly disease option: a sexually transmitted disease. "One of them passes it to the next and then to the next."

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