Insect intelligence: paper wasps display strong long-term memory
Jeremy Hance, mongabay.com
November 30, 2008
A recent study in Current Biology finds that paper wasps are capable of remembering rivals a week after initially meeting. As a highly social insect, the discovery proves that the paper wasps’ social interactions are based on applied memory rather than simple instinct. The finding overturns many ideas about the intelligence of insects.
An important part of the finding is the longevity of the paper wasp’s memory. Michael Sheehan, a graduate student who worked on the study, notes that honeybees remember where they have found nectar in the past, “but those memories are pretty fleeting.”
Not so for the paper wasp. To test their memory Sheenan and Elizabeth Tibbets, assistant professor of ecology and evolutionary biology, videotaped reactions of wasp queens as they met for their first time and again one week later.
Studying the footage, it became clear that the wasps were much more aggressive toward each other the first time they met. The second meeting a week later was a different story: "instead of trying to bite each other and really have a rough-and-tumble encounter, they just sort of hung out next to each other," Sheehan said.
To ensure that the wasps were truly employing individual memories of past meetings, the scientists introduced the wasp to more strangers in-between the first and second encounter. Every encounter with a stranger was characterized by high aggression.
"The interesting aspect of this work is not just that the wasps have a good memory, but that it's social memory," Sheehan commented. "It seems that their specific social history with particular individuals is something they're keeping track of and that it matters to their lives."
Female paper wasps share nests, therefore the ability to remember past encounters with others allows them to not waste energy in aggressive action with individuals whom it has already settled its differences.
Intelligence and applied memory are not terms often associated with insects, even highly social ones. Scientists have long believed that being able to form memories and apply them belonged only to species with large brains. Yet the wasps’ brain is less than a millionth size of our own and can still form important and long-term memories. Such a finding has implications on our concepts of animal intelligence, social cognition, and brain evolution.
Micheal J. Sheehan, Elizabeth A. Tibbetts. Robust long-term social memories in a paper wasp. Current Biology, September 23rd, 2008.
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