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Zom-bees may hold clue to honeybee disorder

February 8, 2012
By RICHARD GAST , Adirondack Daily Enterprise

There's been a surge in the popularity of zombies in pop culture in recent years. So I was particularly interested when a "Scientific American" news article with the headline 'Zombie' Fly Parasite Killing Honeybees' was brought to my attention.

While comic book, movie and TV zombies are often the result of a virus, radiation, witchcraft, spores or extraterrestrials, the invader, in this case, is Apocephalus borealis, a parasitic fly; a member of the family, Phoridae, a group of small, hump-backed flies not unlike fruit flies. A. borealis has long been known to lay its eggs inside of living hosts, including bumblebees and paper wasps, but until now, had never been observed parasitizing honeybees.

Interestingly enough, the discovery came inadvertently, when John Hafernik, a biology professor at San Francisco State university, noticed a number of honeybees behaving oddly; walking in circles on the concrete outside of John S. Hensill Hall, at the University. Professor Hafernik gathered up several of the bees and placed them into a vial. His intention was to feed them to a praying mantis that he had in his lab, but he completely forgot about them until about a week later. When he returned for the vial, it was full of dead bees and tiny live fly pupae. He surmised that parasitic flies had been feeding on the bees. DNA testing revealed the pupae to be A. borealis.

In follow-up studies, grad students set up traps outside of hives belonging to several San Francisco Bay area beekeepers. Infected bees were found in several of the hives.

Researchers believe that adult female Phorid flies land on worker bees while they are away from the hive foraging. They then use a razor-sharp ovipositor, a tail-like egg-laying apparatus, to insert their eggs into the host bee's abdomen. Days later, the eggs hatch and the newly hatched maggots start eating the bees' from inside.

At this point, the infected bees' behavior is altered. They become nocturnal, abandoning the hive during the night, perhaps instinctively knowing that it is the only way to prevent the spread of the parasite that has infected them, to the colony. Whatever the reason, Professor Hafernik has come to call this event, "the flight of the living dead."

The suffering bees, which are often drawn toward light, soon display actions that are wholly unlike those of healthy honeybees. They become completely disoriented, eventually taking to walking aimlessly, often in circles, behaving almost as though they were zombies. Then they die.

Several days later, the maggots push their way out of the dead bees' bodies; exiting between the head and thorax. As many as 15 maggots have been observed emerging from just one bee. The tiny parasites pupate in locations away from the host bee.

As worker bees abandon the hive, the order of the colony can be severely disrupted. Younger, still-developing bees may be forced to take the place of workers that have been lost. Loss of enough workers could potentially lead to collapse.

While scientists, including Hafernik, believe that the flies may be a contributing factor in hive abandonment events that have been occurring worldwide since 2006, commonly referred to as Colony Collapse Disorder, it is not clear that A. borealis is the only cause of the phenomenon, which has devastated many commercial beekeeping operations in recent years. Other parasites, viruses, bacterial infections, pesticides and weakened immune systems, stress and poor nutrition resulting from the impact of human activities on the environment may all have a part in the decline. According to Hafernik, "The best guess is that it's a combination of things. We're hopeful that now that we have a specific organism associated with hive abandonment, maybe we can use that as a window into understanding why bees would leave their hive."

San Francisco State University researchers plan to use radio tags and video cameras to further their research. The hope is that continued research into the Phorid fly will provide additional clues to help them understand and ultimately bring an end to Colony Collapse Disorder.

Albert Einstein was once quoted as saying "If bees were to disappear, man would only have a few years to live." Honeybees are natural pollinators, which are crucial to the healthy production of many important fruit, vegetable, and nut crops, and alfalfa hay. A report by the National Research Council noted that in order to bear fruit, three-quarters of all flowering plants, including most food crops and some that provide fiber, drugs and fuel, rely on pollinators for fertilization.



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