If you were, chances are your nestmates might bite you to communicate that it is time to leave the nest and forage for the colony, according to research by a University of Washington animal behaviorist. Biting is a way that workers in a colony of the social wasp Polybia occidentalis recruit new foragers to gather water, food and building material in a time of need, said Sean O'Donnell, a UW associate professor of psychology.

O'Donnell previously found that biting appears to be an important way of regulating the division of labor among these insects. Now, in the current issue of the journal Animal Behaviour, he describes an experiment in which he artificially removed active foragers from four wasp colonies to see how new foragers are recruited.

He found that biting was directed at certain individuals, who previously hadn't left the nest, to induce them to begin foraging. The rate of being bitten increased by an average of 600 percent for these recruited foragers, while biting rates did not increase for other workers.

"The fact that biting was specifically directed at recruited foragers shows that biting is the mechanism that the colonies used to activate new foragers," said O'Donnell. "With no water, food and building material coming in to the nest, the colonies needed to ramp up their foraging workforce. This study shows that these biting interactions play a central role in recruiting foragers and that biting has a role in communication that affects task performance in a colony."

To study the wasps, O'Donnell first collected and anesthetized an average of about 300 workers from each of the colonies. He then marked each wasp's thorax with a color-coded system that made it possible to identify individuals and returned the insects to their nests. A day later, all foragers returning to a n
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Contact: Joel Schwarz
joels@u.washington.edu
206-543-2580
University of Washington
27-Mar-2006