Cross-posted from Scientific American‘s Observations blog on behalf of Katherine Harmon.
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 US 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% 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.
Read the rest of this story on Scientific American.
Image: Parasitic fly larva emerging from a dead bee’s neck. Courtesy of John Hafernik.