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Wednesday, 3 May, 2000, 18:03 GMT 19:03 UK
Bees trapped by sex sting
The larvae cling on to the male bee
The larvae cling on to the male bee
Through history, many lustful victims have been entrapped by the lure of sex but the natural world has revealed a truly bizarre example of the honeytrap.

Tiny beetle larvae, keen to get into bee nests, gather together in hundreds and impersonate a female bee.

When a male bee succumbs to the perfumed seduction and tries to mate, the beetle larvae grab onto to his chest hair.

Hundreds congregate to imitate a female bee
Hundreds congregate to imitate a female bee
When the male mates with a real female bee, the larvae jump ship. They are then carried into the hives, where they eat the eggs and the food provided for young bees.

It is the first time individual parasites have been seen to team up to attack their host.

Wriggling masses

The research has taken seven years of fieldwork in the Mojave Desert, US. John Hafernik and Leslie Saul-Gershenz, from San Francisco State University, watched the blister beetle larvae emerge from their sandy burrows every spring.

Hundreds of the dark-orange larvae then crawl up to the tip of the nearest plant stem, where they form wriggling masses that roughly resemble female Habropoda pallida bees.

"By first attaching to a male bee, the larvae have access to multiple females and, subsequently, the multiple nests of each female," said Dr Saul-Gershenz.

Dr Hafernik added: "Until now, no other insect has been known to use co-operative behaviour to mimic other species."

Powerful perfume

The researchers also found that the beetles may enhance their sexual attractiveness by using a carefully chosen scent.

They tested for olfactory cues by placing models of the larval groups near real aggregations.

The female carries the larvae in to the nests
The female carries the larvae in to the nests
"The male bees ignored the models completely but hovered or tried to land on the real groups of larvae even before they were formed into a bee-like mass," said Dr Saul-Gershenz.

"The larvae are probably emitting a bee-like pheromone to attract males, and another chemical cue to form aggregations."

The research has been published in the journal Nature.

Dr Ronald McGinley of the Smithsonian Institution's Department of Entomology said the findings raise "exciting questions" for future research.

"How do new-born beetle larvae co-ordinate a collective pilgrimage to individual grass stems? And why is this particular bee species attracted to 'larval clumps'? Is the attraction visual, chemical or both?"

Spanish fly

The wriggling groupings were first reported in 1895 and it was known that the beetles parasitise the bees nests, but it is only now that the two observations have been connected.

Other species which practise aggressive mimicry include the female bolas spider, which attracts its prey by mimicking the female sex pheromone of the armyworm.

Adult blister beetles are so named because of their defensive mechanism of releasing a drop of bright-orange blood laced with the chemical cantharidin. This causes severe pain and blistering upon contact with the skin.

This chemical is also used in the supposed aphrodisiac "Spanish Fly," which, when swallowed, causes severe burning in the urinary tract.

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