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Sexually deceived flies not hopelessly dumb

Pollinators become wary after being tricked into attempting mating with a plant

FOOL ME ONCE  A raised lump of plant tissue (left) growing on the petal of a South African daisy can trick a male bee fly into mating attempts that dust him with pollen — and may, new tests suggest, make him a little wiser. 

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Male bee flies fooled into trying to copulate with a daisy may learn from the awkward incident.

Certain orchids and several forms of South Africa’s Gorteria diffusa daisy lure pollinators by mimicking female insects. The most effective daisy seducers row a dark, somewhat fly-shaped bump on one of their otherwise yellow-to-orange petals. Males of small, dark Megapalpus capensis bee flies go wild.

But tests show the daisy’s victims waste less time trying to mate with a second deceptive daisy than with the first. “Far from being slow and stupid, these males are actually quite keen observers and fairly perceptive for a fly,” says Marinus L. de Jager of Stellenbosch University in South Africa.

Males’ success locating a female bee fly drops in the presence of deceitful daisies, de Jager and Stellenbosch University colleague Allan Ellis say January 29 in the Proceedings of the Royal Society B.

That’s the first clear demonstration of sexual deceit’s cost to a pollinator, Ellis says. Such evolutionary costs might push the bee fly to learn from mating mistakes.

How long bee flies stay daisy-wary remains unknown. In other studies, wasps tricked by an Australian orchid forgot their lesson after about 24 hours. 

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