Wasp Brains: Bigger is Better

When it comes to brains, size does matter.

A study of tropical wasps suggests that bigger brains are tied to social dominance.

Researchers have found that key processing regions in the brains of both males and females of one wasp species not only increased in size with age but were also associated with being dominant.

Sean O'Donnell and Yamile Molina, scientists at the University of Washington, studied a part of the wasp's brain called the calyx, where neural connections are made. While the overall size of the calyces did not differ between the males and females, specific subregions were larger in each sex. Males rely on vision when they leave the nest for mating opportunities, and the part of the calyx that receives visual input was larger. In contrast, most female interaction takes place on the nest, where tactile and odor senses are important and the part of the calyx that received input from the antennae was bigger among the females.

"When you are dominant among insects you get more food," O'Donnell said, "and in this case it gives males more energy to leave the nest and mate. The fact that the males are dominant and long-lived makes this species interesting from a neurobiological standpoint. We think they have pretty sophisticated cognition compared to males of other wasp species."

The research raises important questions about how animals develop the brainpower for social dominance and complicated tasks.

"Do you get to be dominant because of a big brain or does being dominant drive brain size? That's still an open question and we don't know which comes first," O'Donnell said. "This study suggests the high cognitive demands of being dominant drive brain capacity."

The study may help scientists better understand the evolution of human brainpower, he said.

"You are looking at super-distant animals when you compare wasps and people. Yet there may be an interesting commonality between them. Increased brainpower may be part of being social, no matter who you are. What makes this exciting is we see some common patterns in how brains change as societies evolve. As we see changes in social complexity, there are changes in brain structure. If it is good for people it should be good for wolves, dolphins and paper wasps."

The research, funded by the National Science Foundation, has been published in the online edition of the journal Developmental Neurobiology.

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