From: David A Gabel, ENN
Published January 5, 2012 09:34 AM

Study: Parasitic Fly to Blame for Honeybee Population Decline

Populations of honeybee have been in a seemingly unstoppable downward spiral, and scientists are still grasping to find the cause. A new study from the San Francisco State University suggests that one factor may be a parasitic fly, Apocephalus borealis, which lays its eggs in the bees' abdomens. The parasitic eggs cause atypical behavior in the bees, causing them to abandon their hives. Like a scene out of Alien, the eggs eventually hatch and the newborn flies burst out of the bee, killing it in the process.

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The abandonment of the hive may be the primary cause of the so-called colony collapse disorder. Much like fungus can infect the brain, causing erratic behavior; the fly eggs may do the same. Another theory is that this behavior may be a defense mechanism by the honeybee. Knowing they are infected by the parasite, they flee the hive so not to allow it to spread. In the end, unfortunately, this causes the population to consistently dwindle.

New stats show that the US honeybee population dropped 35 percent in just three years, between 2006 and 2009. Similar mass die-offs have occurred around the world in places like Europe, China, and Japan.

The parasitic fly theory was unveiled by John Hafernik, biology professor from San Francisco State University. He collected bees found belly-up on the ground underneath lights by the University's biology building. He put them in a vial and forgot about them. Looking at the vials later, he was shocked to find fly pupae surrounding the bees.

Hafernik's team further studied the parasitic fly’s effects on honeybees. They found evidence of the fly in 77 percent of the hives sampled in the Bay Area, California's Central Valley, and in South Dakota.

They found that the fly lays its eggs in the bee’s abdomen. After a few days, the bee exits the hive, often at night, in a curious flight to nowhere. They fly toward light, unable to control their own bodies. Hafernik's team described the affected bees like zombies, flying erratically and walking in circles with no sense of direction. The bee dies and up to 13 fly larvae crawl out of the bee's neck.

The parasitic fly genus, Apocephalus, has also been known to lay its eggs in army ants. The female will pierce the ants head with a sharp ovipositor and inject the eggs. This eventually causes the head to fall off, often before the ant stops moving around. This horrific behavior has given the parasite the common name, "ant-decapitating fly."

Hafernik recommends that beekeepers around the country collect samples of bees that leave the hive at night. This can be done by setting up a light trap. Pinpointing the extent of the bee behavior can prove vital in isolating affected populations and stopping this possible cause of colony collapse disorder.

The study has been published in the journal PLoS One.

Link to published article: http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0029639

Image credit: John Hafernik

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