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December 17, 1996

Wasps aren’t automatons; they have individuality, says UW researcher

Certain wasps may be far from the simplistic automatons — blindly doing the same tasks day after day throughout their lives — that most people picture when they think of insects.

Instead, wasps show a great deal of behavioral individuality, according to research presented at the annual meeting of the Entomology Society of America last week by a University of Washington psychologist.

“The wasps I studied differ in the jobs they specialize on and in their rates of behavioral development,” said Sean O’Donnell, a UW assistant professor of psychology. “These behavioral differences are key to the function of insect colonies and to the ecological success of social insects.

“There are a range of jobs that need to be done in a wasp colony, just as there are in a business. Among these wasps there is a lot of specialization in the tasks they perform both inside and outside the nest.”

O’Donnell discovered that wasp workers’ job specialization has a strong genetic component, but the rate of individual behavioral development seems to operate free of genetic influence.

“Within colonies, workers that specialized on the same jobs tended to be more genetically similar than those that performed different jobs. This correlation of genetics with behavior applied to both housekeeping jobs inside the nests and to foraging for prey, wood pulp, nectar or water,” he explained.

However, the age when individuals began specialized jobs varied considerably, even among those who were closely related genetically. Some individuals seemingly were idle, doing little or no work, until they were required to respond to the colony’s needs. O’Donnell demonstrated this trait in an experiment in which he damaged several wasp nests to spur repair work.

“This suggests that the rate of behavioral development is very flexible and my research shows that wasps change their rates of behavioral development in response to changes in colony needs for certain jobs to be performed.”

Scientists studying animal behavior are trying to understand what evolutionary forces shape the degree of genetic similarity, or relatedness, within animal societies.

O’Donnell studied colonies of a social wasp called Polybia aequatorialis in Costa Rica. This species belongs to a group of wasps in which new colonies are founded by swarms with multiple queens. Their behavior is marked by a trait called age polyethism or doing different jobs at different ages. At a young age these wasps work inside and on the nest at housekeeping chores. When they get older their work shifts toward foraging and nest defense.

These wasps have been puzzling to science because of the multiple queens who lay their eggs simultaneously. This lowers relatedness within a colony.

To study the behavior of individual P. aequatorialis wasps, O’Donnell collected and reared immature wasps from wild colonies. After the adults emerged, he color- and number-coded the young wasps with paint pens and inserted them into other wild colonies. The wasps will be accepted into a colony if they are placed there during the first 24 hours after hatching.

O’Donnell then carefully observed their work behavior for a number of days, charting the housekeeping and foraging activities of the marked wasps. At the end of the observation period, he collected the marked wasps to gather genetic data and correlate it to behavior.

For more information, contact O’Donnell in Seattle at (206) 543-2315 or on e-mail at {sodonnel@u.washington.edu}.