Behavioral observations showed that non-reproductive foragers and guards are significantly smaller than the queen bee in a nest, although the relative size of individual bees varied from nest to nest. Here's where the flies apparently fit in and are affecting the bees' behavior. The bees nest in hollowed twigs and sticks hanging in the tropical understory and the flies flick their eggs into the entrance to the bee nests. Some of these eggs randomly fall into cells, or chambers, prepared by the bees, each to hold a larva and pollen that the larva eats. The cells are then sealed, so if a cell does contain fly eggs the young flies are competing with the bee larva for a limited amount of food.
"There is a natural size variation in bees and this is based in part on the amount of food available in the cell," said O'Donnell. "A fly or flies in a cell reducing the amount of food could be a potentially important factor. It seems that the more flies in a cell the smaller the bee is. The key here is relative body size compared to nest mates. The larger individuals become queens because they are not dominated."
The researchers were able to culture the bees and flies from individual cells and counted as many as 15 of the tiny flies in a single cell. Some cells did not contain flies.
"This study is a counterintuitive take on parasitic infection. It encourages us to look for complicated ecological relationships between different species. Parasitism may encourage sociality in some situations. Here it is promoting social behavior," O'Donnell said.
|Contact: Joel Schwarz|
University of Washington