How's this for a recruiting pitch? Being bitten.

Paper wasps in Costa Rica bite their nest mates to recruit them for foraging duties, a University of Washington researcher says.

Sean O'Donnell, a psychology professor and animal behaviorist, anesthetized and marked hundreds of wasps in Costa Rica by tapping on their nests and capturing them in bags of ether.

He found that when he removed active foragers from four colonies of Polybia occidentalis, wasps that had never left the nest were bitten six times more frequently than their foraging counterparts. The biting continued - sometimes for hours - until the recruits finally left the nest, he said. The species is a distant relative of paper wasps in the United States.

Wasps lack teeth, but have mandibles with tooth-like projections that can clamp down on objects. "They don't seem to hurt each other," O'Donnell said. He suspects recruits are recognized by chemicals on their bodies or some signal that gives away their age.

Foraging for nectar, other insect prey and the wood pulp necessary for nest building are important functions in wasp colonies, O'Donnell said. But some of the new recruits had to be bitten for several hours before they started to forage.

Wasps have a month-long life span, but only last about six days once they start to forage. "It's a very risky behavior," O'Donnell said.

By studying social insects, O'Donnell and other researchers hope to learn more about how social behaviors evolved in insects and humans.

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