John Hafernik, a professor of biology at San Francisco State University, thinks he knows what’s behind the mysterious disappearance of honey bees. The self-described absent-minded professor collected some of the bees to feed to a praying mantis but forgot about them. He returned to find the bees had been consumed from the inside out by Apocephalus borealis (Figure A), a parasitic fly native to North America. The fly injects its eggs into the bee’s abdomen (Figure B). One week later as many as two dozen larvae emerge at the junction of the head and thorax (Figure C) earning them the name ‘decapitating flies.’

The study, A New Threat to Honey Bees, the Parasitic Phorid Fly Apocephalus borealis, published in the science journal PLoS ONE links the parasite to hive abandonment, known as Colony Collapse Disorder (CCD). It found that parasitized bees leave the hive to gather around lights, where they walk in circles and stumble like zombies. The researchers theorize “A. borealis manipulates the behavior of honey bees by changing a bee’s circadian rhythm, its sensitivity to light or other aspects of its physiology.”

The parasite is already well-documented in bumblebees and paper-wasps, but researchers believe its presence in honey bees is a recent development. “Honeybees are among the best-studied insects of the world,” said Hafernik. “We would expect that if this has been a long-term parasite of honeybees, we would have noticed.”

Unlike bumblebees, honey bees live in large colonies that generate enough heat to survive the winter and may aid in propagating the parasite. The study found that 77% of San Francisco Bay honey bees were infected and warns “the domestic honey bee is potentially A. borealis’ ticket to global invasion.” Host bees on other continents would be naïve to the parasite and especially susceptible to attack. Worldwide agriculture, which is dependent on the bees for pollination, could lose billions. That’s billions with a ‘B.’