A bee's future as queen or worker may rest with par...( Strange things are happening in the...)

Strange things are happening in the lowland tropical forests of Panama and Costa Rica. A tiny parasitic fly is affecting the social behavior of a nocturnal bee, helping to determine which individuals become queens and which become workers.

The finding by researchers from the University of Washington and the Smithsonian Tropical Research Institute is the first documented example of a parasite having a positive affect on the social behavior of its host. This is accomplished by cleptoparasitism in this case fly larvae stealing food from the developing immature bees. The researchers found that smaller bees that emerge in a nest are dominated by their mothers. These small bees are more likely to stay and act as helping workers, while larger bees tend to depart and start new nests as egg-laying queens. Bees that emerge from cells, or brood chambers, that also house flies are smaller than their nest mates from fly-free cells. The flies may encourage worker behavior in some bees.

"We often think of parasitism in terms of it affecting an animal's fitness, its survival or its ability to reproduce," said Sean O'Donnell, a UW associate professor of psychology and co-author of the paper appearing in the current issue of the Journal of Insect Behavior. "Here the parasite is not living inside another animal, but is still stealing resources from the host.

"We think these fly parasites are not affecting the lifespan of the bees, and the bees' mothers benefit by having a helper, or worker, stay around to protect the nest, increasing survivability."

O'Donnell and his colleagues studied two closely related tropical social bees, Megalopta genalis and Megalopta ecuadoria, and a family of very small parasitic flies called Chloropidae.

The bees are important pollinators of night-blooming plants and the female bees can nest alone or live in small colonies. A colony is typically made up of two to four individuals a quee
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