Parasitic flies that take over the bodies of honeybees may at last provide another clue into why honey bee colonies have been collapsing at an alarming rate.
Since 2007 hives across the US have been deserted by bees who have gone missing without an apparent cause, decimating colonies across the country. A combination of factors had been blamed for the decline in numbers, ranging from parasitic mites to the effects of pesticides.
However, new findings published in Plos One show a more gruesome threat to bee numbers: the discovery that honey bees may be falling prey to a paristic fly that causes the bees to fly around in the night before killing them, with the offspring of the fly eventually emerging from the remains of the honey bee.
John Hafernik of San Francisco State University in California and colleagues discovered that hosting Apocephalus borealis, a parasitic fly found throughout North America, makes bees fly around in a disoriented way at night, when they normally roost in the hive, before killing them.
Although unlikely to be the sole cause of colony collapse disorder, Hafernik thinks the parasitic fly discovery may help explain why bees quit their hives. “They seem to leave their hives in the middle of the night on what we call the ‘flight of the living dead’,” he says.
Honey bee colonies are subject to numerous pathogens and parasites. Interaction among multiple pathogens and parasites is the proposed cause for Colony Collapse Disorder (CCD), a syndrome characterized by worker bees abandoning their hive. Here we provide the first documentation that the phorid fly Apocephalus borealis, previously known to parasitize bumble bees, also infects and eventually kills honey bees and may pose an emerging threat to North American apiculture. Parasitized honey bees show hive abandonment behavior, leaving their hives at night and dying shortly thereafter. On average, seven days later up to 13 phorid larvae emerge from each dead bee and pupate away from the bee.
The parasitic flies have now been found at 77% of sites in the San Francisco Bay area and their presence has been detected in hives in South Dakota and California’s Central Valley.
The team will now investigate if the so-called “zombie” flights the bees have been forced to undertake are because the parasite affects the bee’s “clock” genes that govern when the bees are active. An alternative theory is that the bees may be ejected from the colony by other bees in order to save the hive from further infection.
As mentioned above, the parasite is unlikely to be the sole cause of declining honey bee numbers but this new finding may provide a clue that can eventually lead scientists to a solution on how to help honey bee populations recover.
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