Wasps Bite to Divide Labor

July 2, 2001 -- It pays to bite the one that feeds you. If you're a wasp, that is.

New research has found a common Costa Rican wasp uses biting — from mild chewing to aggressive group biting — to divide labor in its colony, according to a study published in the current issue of Animal Behavior.

Wasps that are bitten are prompted to fly out of the nest and seek food for the group, either nectar, eaten by adults, or other insects, which are fed to young wasps. Wasps also foraged for wood and water for building the nest.

Most interesting, says Sean O'Donnell, a professor of psychology at the University of Washington and author of the study, is that the biting is completely unrelated to competition over reproduction. In many other insect societies, aggressive behavior also inhibits submissive individuals from breeding.

"We don't really understand what leads individuals to be biters or targets of biting," he says. But the more a wasp was bitten, the more likely it was to leave the colony to forage.

He noted that some wasps spent their lives as either biters or recipients of bites, but most of the wasps spent time as both.

Wasps Painted on the Abdomen

O'Donnell, who has studied the half-inch black and yellow Polybia occidentalis wasp for the past 12 years, captured nearly 800 female worker wasps for the study. Males were not included because they do not live or work with the colony.

He painted color-coded dots on their thoraxes so he could track their interactions, ranking the biting behavior from very mild to slow chewing to highly aggressive biting. Sometimes several wasps ganged up on a single individual. Wasp mouths, or mandibles, have no teeth but do let the insects bite and chew.

In the wasps, most of the biting lasted less than 30 seconds, but some extended for as long as 10 minutes.

"Nest mates seem to agree that an individual should be bitten," he says. "I really think it's because they're unpopular."

Although most of the time the biting appeared not to cause pain, some individual wasps tried to flee their attackers. But none of the wasps was ever injured during the biting sprees.

"Sometimes it just makes me laugh when I watch them," O'Donnell says.