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“Zombie” Fly Parasite Killing Honeybees

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A parasitic fly landing on a honeybee. Courtesy of Christopher Quock

A heap of dead bees was supposed to become food for a newly captured praying mantis. Instead, the pile ended up revealing a previously unrecognized suspect in colony collapse disorder—a mysterious condition that for several years has been causing declines in U.S. honeybee populations, which are needed to pollinate many important crops. This new potential culprit is a bizarre—and potentially devastating—parasitic fly that has been taking over the bodies of honeybees (Apis mellifera) in Northern California.

John Hafernik, a biology professor at San Francisco State University, had collected some belly-up bees from the ground underneath lights around the University’s biology building. “But being an absent-minded professor,” he noted in a prepared statement, “I left them in a vial on my desk and forgot about them.” He soon got a shock. “The next time I looked at the vial, there were all these fly pupae surrounding the bees,” he said. A fly (Apocephalus borealis) had inserted its eggs into the bees, using their bodies as a home for its developing larvae. And the invaders had somehow led the bees from their hives to their deaths. A detailed description of the newly documented relationship was published online Tuesday in PLoS ONE.

The team performed a genetic analysis of the fly and found that it is the same species that has previously been documented to parasitize bumblebee as well as paper wasp populations. That this parasite hasn’t previously been reported as a honeybee killer came as a surprise, given that “honeybees are among the best-studied insects of the world,” Hafernik said. “We would expect that if this has been a long-term parasite of honeybees, we would have noticed.”

The team found evidence of the fly in 77 percent of the hives they sampled in the Bay Area of California, as well as in some hives in the state’s agricultural Central Valley and in South Dakota. Previous research has found evidence that mites, a virus, a fungus, or a combination of these factors  might be responsible for the widespread colony collapse. (Read more about colony collapse disorder in our feature “Solving the Mystery of the Vanishing Bees.”) And with the discovery that this parasitic fly has been quietly killing bees in at least three areas, it might join the list of possible forces behind colony collapse disorder.

Parasitic fly larva emerging from a dead bee's neck. Courtesy of John Hafernik

The parasitic fly lays eggs in a bee’s 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 bee’s 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 it’s while the bees are out foraging because we don’t see the flies hanging around the bee hives,” Hafernik said. “But it’s still a bit of a black hole in terms of where it’s 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.

Hafernik and his colleagues hope that the simple way they made their discovery “will enable professional and amateur beekeepers to collect vital samples of bees that leave the hive at night”—with a light trap, for instance—and keep them around for a week or so to observe for any signs of emerging larvae. Pinpointing the extent of this strange bee behavior could be key to stemming colony collapse disorder by possibly allowing keepers to isolate affected populations. If the parasitic fly is just starting to infect honeybee populations, this could be an important move, especially given the newly prevalent mobile commercial hives, which mean that honeybees—and their ailments–are on the move in much greater numbers than ever before.

Katherine Harmon Courage About the Author: Katherine Harmon Courage is a freelance writer and contributing editor for Scientific American. Her book Octopus! The Most Mysterious Creature In the Sea is out now from Penguin/Current. Follow on Twitter @KHCourage.

The views expressed are those of the author and are not necessarily those of Scientific American.

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  1. 1. ASHIK 12:38 pm 01/4/2012

    Natures rules are sometimes very cruel.What may be the factor for ancestor of flies to figure out to lay eggs on bees abdomen to rise their young?Interesting.

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  2. 2. ErnestPayne 2:05 pm 01/4/2012

    Wow. Congratulations.

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  3. 3. EyesWideOpen 2:24 pm 01/4/2012

    Question to author or any other knowledgable source:

    Since I live in northern California, my question is what would prevent this fly from planting its eggs under the skin of hikers or campers at night within the infection zone? Would the parasite migrate and feed on human brain tissue? If it likes honeybee tissue it may consider human brain tissue a “delicacy.”

    And just what region surrounding the human skull would mature flies “bust out” of? I would imagine the answer is the sinus cavity (i.e. mature flies exiting the nose and mouth while the camper slept). Also, the type of psychosis that brain infection could trigger may pose a threat in the form of unpredictable, perhaps violent or risky behavior. For example, if the parasite can “bust out” of the head region of the honeybee’s body, what would prevent it from “busting out” of any region of the body that furthers the parasite’s goals of mass infection? What I’m getting at, to put it indelicately, is the possibility an human adapted species of this parasite could “bust out” of the human appendage during intercourse, or transfer from one mouth to another during kissing or other intimate contact. Parasites are known to use a species’ own behavior to adapt its behavior in order to exploit the opportunity for spreading to other hosts.

    This highlights the necessity of taking protective measures similar to if one was hiking, camping, or even passively visiting Amazon jungles or other areas with exotic diseases!

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  4. 4. HBobber 5:16 pm 01/4/2012

    “Zombees” is spelled wrong.

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  5. 5. Seamas1 8:05 pm 01/4/2012

    How many flies affecting single bees does it take to reduce a hive?

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  6. 6. buddhacosmos 9:34 pm 01/4/2012

    oh!mygod! it’s bursting out of my NECK! please stop them -aaaarrggghgghggh! (to the tune of “Flight of the Bumblebee”)

    then, again say, it could be the end of agriculture and mass starvation. I think next a GMO that kills ZombeeFly larvae. it just keeps getting worse.

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  7. 7. ray1126 11:11 pm 01/4/2012

    I got 3 letters for you ((((((DDT))))) we need to lift the bane on using this wonderful chemical that when sprayed on crops kills most deadly parasites. Freaking Me First Generation and the crap they have done to the US and other countries is almost unforgivable

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  8. 8. DiJiT 3:14 am 01/5/2012

    OMG. Two years ago it was worse but in Southern California, I have seen bees acting just like this; wandering aimlessly, near light at night/morning with death following. At least there is some sort of answer.

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  9. 9. dhdonaghe 8:24 am 01/5/2012

    This is an interesting article.

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  10. 10. pjac461 9:08 am 01/5/2012

    This really seems like part two of a story I read a couple of years ago. It seems the University of Texas has been doing research to exterminate red fire ants which are prolific in Texas. What did they choose to do? Why release fly that is not indiginous to the US that lays it s egs in the thorax of its victim which kills it (the victim) when the eggs hatch. Does this sound even remotely familiar? See for yourself….
    Why do so many try to “play God” with things they have no business trying to manipulate?
    I am no biologist, so I have no 10 million dollar study to back up my observation, but this just seems way too coincidental.

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  11. 11. pjac461 9:08 am 01/5/2012

    For the above article see this site…

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  12. 12. sholden 5:02 pm 01/5/2012

    @pjac461, yes I’m sure that that introduced fly you mention just magically morphed into the completely different genus and native to North America fly that this article talks about.

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  13. 13. dixie1 8:50 am 01/6/2012

    as a side note….the honey bee is not native to North America. Originally called the European honey bee or the Italian honey bee…most of the honey bees we have in the U.S. are of Italian stock, some are of Russian stock, and others (darker colored) are sometimes referred to as of German stock….by and large the Italian strain is most prevalent in North America.

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  14. 14. Luna_the_cat 6:31 pm 01/7/2012


    Your logic fail:

    1. DDT was banned in the US* not just because it was killing birds of prey, but also because overuse encouraged the evolution of crop pests to develop resistance;
    2. It would kill bees just as readily and as fast as it would kill any fly parasitising bees. It is an INSECTICIDE; bees are INSECTS.

    Your little “OMG Me First Generation” rant reveals nothing but your lack of education on the subject or analytical ability, here. Might want to fix that.

    *Contrary to what you probably believe, DDT was *never* banned worldwide, and is still used in some areas for mosquito control; in many other areas it is no longer used, not because it was banned, but because mosquitoes evolved resistance to it and it is pointless.

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  15. 15. verdai 5:30 pm 01/10/2012

    Refer to your other current article on the emotions of honeybees while seeing this picture-

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  16. 16. Ethnobeeology 2:30 am 01/11/2012

    Monsanto has bought out Beelogics – what is next? You were told that eating GE food had no effects, you just poop the GE DNA out – now we find that GE bee-foods (Remebee & RemebeePro), are being pushed by the USDA/Monsanto/Beelogics through the EPA examination process for commercial use in the US, because it alters the bees’ gene expression to be better able to avoid IAPV & CCD- whats next? – Patented GE bees that can handle pesticides? Not good for non-corporate beekeeping, our declining native bee species, or our common future. Monsanto has no qualms about GEing and patenting things that kill ALL non-patented non-GE life-forms. Recent research shows that yes, ingesting GE-food can influence gene expression in the consumer – proofs in the pudding.

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  17. 17. bucketofsquid 11:43 am 01/16/2012

    Clearly we need something that specifically targets the parasitic fly but is harmless to the bees. It shouldn’t take long to figure out a fix. We already have treatments for the other identified culprits that work with various degrees of success.

    If I ever buy land outside the city I’m going to get a bee colony going. I have to be carefull though because I’m allergic to bee stings.

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  18. 18. cinque_verdi 10:58 am 04/17/2012

    You don’t need to buy land to start a bee colony.
    Here in London we do it on top of buildings and is incredible the amount of support we get.
    It is very rewarding but make sure you have the permission.

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  19. 19. m0nty 3:40 pm 05/14/2012

    Pretty sure I’ve seen a Zombie Fly. Well, one for humans anyway?

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  20. 20. old south honey 1:48 am 12/9/2012

    Get involved and keep your own bees!

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