Body-Snatching Flies


John Hafernik, a biology professor at San Francisco State University, collected a supply of dead honeybees (Apis mellifera) from the ground underneath the lights around the University campus to feed his newly captured praying mantis. “But being an absentminded professor, ” he said, “I left them in a vial on my desk and forgot about them.” When he thought of them again a few days later, he said, “. . . there were all these fly pupae surrounding the bees.”

We now know a tiny parasitic fly (Apocephalus borealis) lays her eggs in the abdomen of a living bee, using it as home and food for the larvae which crawl out of the eggs. Several days later, the bee will stumble out of its nest and fly toward the nearest light, unable to control its own body. After it dies, up to 13 larvae will crawl out of its neck and pupate nearby.

For the last several years, in North America and certain other parts of the world, honeybee populations have declined sharply, a condition known as “colony collapse disorder”. This is extremely important because the bees are necessary to pollinate many of our most essential food plants, as well as to make honey.

It is thought now this fly, which also attacks bumblebees and paper wasps, may be one of the main reasons for the honeybees decline. Hafernik believes the fly may have only recently begun feeding on honeybees. He says honeybees have been studied so thoroughly that the parisitization would likely have been discovered sooner if it had been happening long.

However, his team found evidence of the parasites in 77% of the bee hives studied in several areas of the U.S. Ordinarily, it would seem unlikely the new relationship would spread so quickly. But commercial hives of bees are trucked around the country so often to pollinate fields that we may have spread it ourselves.

A citizen science project called ZomBee Watch is now tracking the parasite to learn more about it. It has a website at

 Source: Scientific American, March 2012, page 14, Body-Snatching Flies


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