How does an insect with a brain the size of a poppy seed decide to carry out a particular task? The answer, says a team of Stanford University biologists, has less to do with brainpower than with the ant`s extraordinary sense of smell. Writing in the journal Nature, the Stanford scientists found that, when a parade of patroller ants returns to the nest, their distinctive body odor cues other workers to go out and forage for food. This new insight into the behavior of social insects is the latest discovery to emerge from a 20-year field study of red harvester ants (Pogonomyrmex barbatus) in the southern Arizona desert - a project designed and led by Deborah M. Gordon, an associate professor of biological sciences at Stanford.
"The question is, how does a worker know what to do?" said Gordon, coauthor of the May 1 Nature study. "There's nobody in charge, there's nobody telling it what to do."
A mature colony of red harvester ants consists of a single queen and 10,000 to 12,000 female workers. The lifespan of a worker is only one year, but a queen can live 20 years and produce thousands of new workers annually. In fact, egg-laying is the queen's only responsibility. She has nothing to do with running the colony or assigning workers to specific tasks.
Understanding the subtle cues and interactions that enable small-brained insects to build elaborate communities has become a major area of research, not only for biologists but also for engineers trying to solve intricate problems in computer science, network communications and even robotics.