Popular wisdom reminds people not to bite the hand that feeds them. But Sean O’Donnell has found a species of social wasp that bites its fellow workers, prompting them to leave the nest and forage for the colony.

O’Donnell, a UW assistant professor of psychology, found that the behavior of the wasps, Polybia occidentalis, was not related to competition over reproduction or to body size. Rather, the biting interactions seem to be a means of regulating the division of labor in insect colonies.

	Sean O'Donnell. Photo by Kathy Sauber.

O’Donnell’s findings were based on detailed observation of wasp colonies in a dry tropical forest in Costa Rica. He captured nearly 800 female workers from three colonies, color-coded them with dots of paint on their thorax, and observed their interactions.

The intensity of biting behaviors varied, ranging from mild to severe. Recipients of severe biting often appeared to do their best to escape. “These are not different behaviors but a continuum of the same behavior, and the intensity of biting can transition to a more aggressive form during an interaction,” says O’Donnell.

In addition, he observed that some individuals were the victims of simultaneous or serial biting. As many as six wasps were observed biting another individual simultaneously. Biting interactions typically lasted less than 30 seconds, but a few were extended for as long as 10 minutes.

“Biting seems to have a cumulative effect on the behavior of these wasps,” O’Donnell says. “As the number of incidents and severity of biting increase, the likelihood of an individual leaving the nest to forage increases.”

His observations show that an individual wasp’s behavioral development tends to follow a pattern. The individual begins working inside the colony’s nest and then progresses to the outside, where it engages in biting behavior. When a worker becomes the target of biting, she goes off to forage. However, some individuals seem to specialize either as biters or recipients of biting.

“This was not related to ovary development or body size so this behavior does not seem to be connected to reproductive status,” he says. “We don’t know what drives biting behavior. There is a possibility that it might be genetic, or it could be chemical because we do know that social insects tend to communicate chemically.”

O’Donnell plans further work to determine the factors that elicit wasps’ biting behavior.

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Using fMRI Technology to Probe Musical Comprehension

[Winter/Sping 2002 - Table of Contents]