The parasitic fly lays eggs in a bees abdomen. Several days later, the parasitized bee bumbles out of the hives often at night on a solo mission to nowhere. These bees often fly toward light and wind up unable to control their own bodies. After a bee dies, as many as 13 fly larvae crawl out from the bees neck. The bees behavior seems similar to that of ants that are parasitized and then decapitated from within by other fly larvae from the Apocephalus genus.
When we observed the bees for some time the ones that were alive we found that they walked in circles, often with no sense of direction, Andrew Core, a graduate student who works with Hafernik and a co-author on the new paper, said in a prepared statement, describing them as behaving something like a zombie. (Read about other parasites that turn their hosts into zombies in the article Zombie Creatures.)
Bees from affected hives and the parasitizing flies and their larvae curiously also contained genetic traces of Nosema ceranae, another parasite, as well as a virus that leads to deformed wings which had already been implicated in colony collapse disorder. This double infection suggests that the flies might even be spreading these additional hive-weakening factors.
The research team plans to track bees with radio tags and video cameras to see whether infected bees are leaving the hive willingly or getting kicked out in the middle of the night and where the flies are finding the bees in which they lay their eggs. We assume its while the bees are out foraging because we dont see the flies hanging around the bee hives, Hafernik said. But its still a bit of a black hole in terms of where its actually happening. Most of the parasitized bees found so far have been foraging worker bees, but even if other groups of bees within a hive are not becoming infected, a decline in the number of foragers in a hive could have a large impact on a hive as a whole. Models of colony dynamics suggest that significant loss of foragers could cause rapid population decline and colony collapse, the researchers noted in their paper.
