Sept. 22, 2008 -- Many terms for socializing, such as "social butterfly," "queen bee," and "the buzz," come from the insect world, and now it seems at least one species, the paper wasp, deserves its reputation.
Female paper wasps can't perform an "air kiss," hug or shake hands, but like humans, they look each other over and remember individuals for at least a week after first meeting them. They then base subsequent encounters on these first impressions.
Scientists previously thought only humans and other big-brained creatures could remember social encounters over long periods of time, with insects possessing more fleeting memories. Since the paper wasp brain is less than a millionth the size of our brains, some assumptions about social cognition now appear wrong.
"Wasps have a complex social life because any individual is potentially capable of reproducing," co-author Elizabeth Tibbetts told Discovery News.
She explained that multiple females join to create a single nest, some dominating others and laying most of the eggs. The subordinates must then "work hard to feed and care for the offspring."
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"Everyone works together to defend the nest and raise the young, but there is also conflict over work rates and the sharing of food and reproduction," added Tibbetts, an assistant professor of ecology and evolutionary biology at the University of Michigan.
In prior research, she and colleague Michael Sheehan found that the female wasps sniff and look each other over when they first meet, taking note of unique facial markings. The researchers therefore suspected the wasps would act less aggressively around familiar faces than they would around strangers.
To test this, the researchers videotaped and measured aggression between 50 wasp queens in four different encounters over eight days. They first placed two wasps, which had never met each other before, in an observation chamber. The scientists then separated the two and returned them to a communal cage with other wasps. A week later, the pair met again.
The differences between their behaviors, outlined in the latest issue of Current Biology, were striking. To put it mildly, female wasps aren't partial to strangers.
"The unfamiliar wasps fight," Sheehan described. "One of them snaps its mandibles a lot at one and eventually, at the end, bites the (other's) leg and pulls the wasp across the container."
When two familiarized wasps meet again, "they just hang out next to each other grooming themselves."
As for male paper wasps, they "all have the same faces," Sheehan said. "It is unlikely that they can tell individual males apart. Males don't really need to know particular individuals since they don't compete or fight with the other members of their nest the way females do."
Since females share nests, remembering whom they've settled differences with makes for a more harmonious home life and keeps them from wasting energy on repeated scuffles.
Anna Dornhaus, assistant professor of ecology and evolutionary biology at the University of Arizona, told Discovery News that the discovery that wasps remember social encounters "is a great finding, although I am not too surprised."
"Insects are often supposed to be simple, genetically predetermined behaviorally, but many studies show that this is not at all the case," she explained. "Insects, especially bees, wasps and ants, have been shown to have extraordinary learning skills, and their social environment is very important to them."
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