- The honey bees become disoriented after the parasite lays its eggs in its abdomen.
- The honey bees abandon their hives in a "flight of the living dead."
- The flies had been determined earlier to parasitize bumble bes.
American scientists have discovered that a fly parasite can turn honey bees into confused zombies before killing them, in an advance that could offer new clues to why bee colonies are collapsing.
So far, the parasite has only been detected in honey bees in California and South Dakota, American researchers reported in the open access science journal PLoS ONE this week.
But if it turns out to be an emerging parasite, that "underlines the danger that could threaten honey bee colonies throughout North America," said the study led by San Francisco State University professor of biology John Hafernik.
Hafernik made the discovery by accident, when he foraged some bees from outside a light fixture at the university to feed to a praying mantis he'd brought back from a field trip.
"But being an absent-minded professor, I left them in a vial on my desk and forgot about them. Then the next time I looked at the vial, there were all these fly pupae surrounding the bees," he said.
Soon, the bees began to die, but not in the usual way by sitting still and curling up. These bees kept trying to move their legs and get around, but they were too weak, said lead author Andrew Core, a graduate student in Hafernik's lab.
"They kept stretching them out and then falling over," said Core. "It really painted a picture of something like a zombie."
Further study showed that bees that left their hives at night were most likely to become infected with the fly parasite, identified as Apocephalus borealis.
Once bees were parasitized by the fly, they would abandon their hives and congregate near lights, a very unusual behavior for bees.
"When we observed the bees for some time -- the ones that were alive -- we found that they walked around in circles, often with no sense of direction," said Core.