THE underclass rarely decides on who gets to be royalty, and despised interlopers never do. Yet in certain bee societies, a tiny parasitic fly has a big influence on which bee becomes queen. Not only that, the fly dictates the status of many of her subjects.
Sean O鈥橠onnell of the University of Washington, Seattle, and colleagues Adam Smith and William Wcislo of the Smithsonian Tropical Research Institute in Balboa, Panama, made the discovery while studying a species of sweat bee that lives in the tropical forests of Panama and Costa Rica.
Megalopta genalis lives in colonies, where young female bees develop inside cells stuffed with nutritious nectar and pollen. A small parasitic fly called Fiebrigella can also lay its eggs inside these cells. When they hatch, the larvae steal the food stores, which stunts the developing bee鈥檚 growth.
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That has a profound effect on the bee鈥檚 future. Large, well-fed bees stand a good chance of leaving the nest and starting a new colony as reproducing queens. Their stunted relatives, in contrast, have little chance of succeeding as colony founders. The best way to pass their genes on to the next generation is to become sterile workers labouring for the queen that bore them, which helps her to reproduce and pass down genes to the workers鈥� sisters on their behalf. So the actions of the fly indirectly dictate who takes the crown (Journal of Insect Behavior, ).
鈥淭he best way for stunted female bees to pass on their genes is to become sterile workers, labouring for the queen鈥�
鈥泪苍 Megalopta, the parasites promote sociality,鈥� says O鈥橠onnell. His study is the first to show that a parasite can actually encourage group living in its host, he says.
This effect comes as a surprise. Biologists have assumed that parasites discourage sociality, because parasitism could easily sweep through crowded colonies. However, the Fiebrigella fly does not spread from one bee to the next within a colony and so does not discourage crowding.
It has long been thought that environmental pressures that restrict the reproduction of individual insects might lead them to help their relatives reproduce instead, and that this could be one route by which true sociality may have evolved.
More than a decade ago, O鈥橠onnell argued that a parasite could act as that driving force, and his prediction is supported by this new research. But he never expected that it might happen in such an indirect and subtle way, he says.
It remains to be seen whether something similar happens in other insect species, though O鈥橠onnell suspects it might.
