Honeybees were already facing colony collapse in the Northwest when a Northwest researcher discovered they were also falling victim to a new horror: the zombie fly.
Ramesh Sagili, a honeybee specialist at Oregon State University, discovered the region’s first honeybee to be infected by the zombie fly, which already has been found to afflict honeybees in California and South Dakota.
The OSU researcher was already on the lookout for afflicted bees.
He had set traps for them around the Corvallis campus when he was walking to work on a July morning. “I just look to see if I can find any honeybees around … and I found these two dead bees on the sidewalk,” Sagili said.
He picked up the fallen insects, carried them in the palm of his hand to his laboratory, and placed them in a vial. Four days later, seven larvae broke off the bee’s head and crawled out of its neck. Three weeks later, one of them matured into an Apocephalus borealis fly.
The insects are commonly called zombie flies because they trigger a disoriented, zombie-like behavior in their hosts. According to ZomBee Watch, a project of San Francisco State University, honeybees infected by the zombie fly leave their hives at night and are attracted to nearby lights where they become stranded and eventually die.
Bumblebees have long been known to host these parasitic flies, which lay their eggs in the bee’s abdomen.
Walter S. Sheppard, chairman of Washington State University’s Entomology Department, confirmed that Sagili’s discover marks the first known case of honeybees in the Northwest being infected by zombie flies.
Honeybees around the country have been hit by a mysterious phenomenon called colony collapse disorder. Since 2006, researchers have been looking for clues to explain why adult honeybees have disappeared from their hives, either entirely or in large numbers. The disorder has been a big concern for Northwest beekeepers and growers who rely on honeybees to pollinate their fruit, berry and other crops. In Oregon, beekeepers lost about 25 percent of their hives from 2009 to 2010.
Possible causes include mites, viruses, malnutrition, pesticides, a lack of genetic diversity and the stress of being kept in commercial hives and trucked from farm to farm to pollinate crops.
Sagili said it’s too early to add zombie flies to the list of possible causes of honeybee colony collapse.
“Currently it’s not a threat, but we need to be vigilant and monitor the prevalence and intensity of this parasite to make sure it doesn’t become another problem to the already struggling bees,” he said. “We already have several other stress factors that are acting on the bees.
Sagili said “zombie fly” is not a term he uses.
“I still call them decapitating flies because that’s how the bee literally dies. The head falls apart because the larvae comes out of the neck,” he said. “Zombie fly is (used) just to get more attention.”