|
'Indestructible'
male cockroaches fall prey to their fatal attraction to
sex
By Toby
Harnden
(Filed:
20/02/2005)
As generations of pest controllers and
embattled homeowners know only too well, cockroaches are
supposedly hardy enough to survive anything - even a
nuclear war. Now, however, scientists are exploiting the
weakness that could consign the insects to oblivion:
their rampant sex drive.
After a quest of more than a decade, they
have discovered how to create an artificial version of
the sexual pheromone produced by willing female German
cockroaches – a scent so irresistible that even males
close to death by starvation will pass up a lump of meat
when they catch a whiff. By spraying the scent on
cockroach traps, a fatal attraction can be set up.
What Dr Coby Schal, an American
entomologist who first became obsessed with cockroaches
almost 30 years ago, described as "the ultimate eureka
moment" came recently at a pig farm. Male cockroaches
began scuttling towards the synthetic pheromone, proving
it was indistinguishable from the real thing.
Just one female German cockroach – the
most common variety of the pest found in Britain – can,
in ideal conditions, trigger a breeding cycle resulting
in a million new cockroaches within a year. Each insect
can lay one egg a month; each egg contains 40 babies.
Female cockroaches can produce eggs when they are a
month old: preventing fertilisation became a holy
grail.
The urge for male cockroaches to mate
with virgin females is much stronger than the desire to
gorge. The scientists discovered that they would head
for the females – or traps laced with the synthetic
pheromone – from up to 16 feet away.
On the other hand, the females prefer to
eat. They have sex only once but continue reproducing
throughout a lifespan of up to nine months. It was only
in 1993 that scientists discovered the natural
pheromone, released when the female lifts its wings and
lowers its abdomen.
The creation of the artificial version,
announced in an article last week in Science magazine by
Dr Schal and four other scientists, took another 10
years.
First, they had to separate the males,
juveniles and impregnated females. Then, 15,000 virgin
cockroaches were dissected to yield enough pheromone for
a proper study.
In the history of the battle between
mankind and cockroaches, however, this time is a mere
blip. Fossils suggest that cockroaches have been on
Earth for more than 200 million years. They eat almost
anything.
"Studies have shown that doses of
radiation that would kill a mammal have a negligible
effect on cockroaches," said Dr Schal, who keeps
millions of cockroaches in glass tanks smeared with
Vaseline in his laboratory at North Carolina State
University.
More than $1 billion (£528 million) a
year is spent in the United States in attempts to kill
cockroaches and other insects. Cockroaches spread
diseases including dysentry and cholera, and can cause
asthma in children.
Dr Schal warned against prematurely
declaring victory over the cockroach. A maximum of half
the adult population could be seduced by the artificial
pheromone and, in tests, only 80 per cent of males
responded to it.
He also confessed to mixed feelings about
their extermination. "There are 4,000 species of
cockroaches and less than one per cent of those are a
pest," he said. "A lot of the aversion to them is
social.
"Cockroaches do some amazing things. They
can communicate by sound, visually and through
pheromones. I really enjoy observing them,'' he said.
"Having said that, I also study ways to kill them."
|
.gif)
