Brain, behavior may have changed as social insect coloni...( s and observed their behavior. Later ...)

s, and observed their behavior. Later these individuals were recaptured and their brains were examined. Data showed that calyces were larger among the queens and the stay-at-home females. This is the opposite of what a number of researchers have found among highly social species with large colonies sizes. Several years ago, O'Donnell and his UT collaborators found that among Polybia aequatorialis, a highly social wasp that also lives in the same region of Costa Rica, there is more individual work specialization and individuals take on a sequence of jobs as they age. In such highly social species, workers that leave the nest to forage generally have better-developed brains.

"It seems pretty clear that primitively social colonies were the ancestral condition and that highly social colonies developed and evolved from them, said O'Donnell. He added that what is intriguing is that the pattern of brain development found in Polybia, a highly social group of wasps, is the same as in honey bees, another highly social insect.

"This shows that what job you do puts pressure on brain development in the highly social species," he said. "In contrasts, status seems to be the major brain demand in the primitively social species. This research suggests that task behavior and brain development has changed in a fundamental way between primitively social and the larger more complex social insect colonies."

The work is important because O'Donnell said social insects are a great model for understanding the design of brains and the relationship between brain design and social complexity. "And it has implications for human society because the evolution of our own society may affect brain development. Social behavior places pretty heavy demands on the human brain."

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Contact: Joel Schwarz
joels@u.washington.edu
206-543-2580
University of Washington
15-Nov-2006

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