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Looking for 'zom-bees'

Bees affected by parasitic fly which lays eggs in host

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COLLINSVILLE — Around the end of March, Lynn Berry of Collinsville was noticing dead bees under his garage door.

It’s common for 100 bees to die every day – “They work themselves to death,” he said – but not to find 20 to 40 dead bees under his garage light.

Recent programs at beekeepers meetings he had attended got him to thinking. The state beekeeper had talked about “zombie bees” – bees which are attacked by the parasitic fly Apocephalus borealis. “When I saw more dead bees, I looked into it,” Berry said.

Apocephalus borealis, commonly called the zombie fly, lays eggs in the abdomen of a bee. “As the eggs hatch they eat their way out of the bee, which disrupts their nervous system,” said Virginia Cooperative Extension Agent Melanie Barrow.

“That’s why they call them zombie bees: They (the bees) do not behave the way they normally behave,” Barrow said. They fly at night, whereas normal behavior would be to be back in the hive, or they walk “in complete circles on the ground, like they’ve lost their whole radar system.”

ZomBee Watch

Berry visited zombeewatch.org, for the ZomBee Watch program run by San Francisco State University. Following its instructions, he took samples for testing.

His first round of samples didn’t turn out well, he said. He had put the dead bees in an airtight, sealed container, and nothing happened.

The next time, he left the dead bees in a bag with a crack to let in air. After about a week, pupae hatched out. He sent the results and pictures to the lab.

John Hafernik, who runs the ZomBee Watch, asked Berry to send in the bees. After studying them, Hafernik “said, ‘Yes, one of your bees did test positive for this parasite,’” Berry said.

“‘The bad news is that yes, you have it. The good news it is it’s only one out of 20,’” he said the expert told him.

“They were all excited about it. I’m like, I’m not really that excited about it because it’s just another problem we have to deal with as beekeepers.”

Scuttle flies

Dr. Joe Keiper, executive director of the Virginia Museum of Natural History, said the zombie fly belongs to the Phoridae family, also called scuttle fly.

The name comes from the jerky way of walking when they land; they are also called “humpbacked flies” due to their appearance.

“A very common species (of scuttle fly) inhabits Martinsville (Megaselia scalaris) and can be found in compost piles and unattended trash cans. This species’ habits are typical for the scuttle flies,” he said.

The Apocephalus genus of scuttle flies has 24 species, Keiper said; most of them use ants as hosts. Ants and bees are closely related, he said, and Apocephalus borealis is known to attack bees and wasps instead of ants.

‘Quite a bit of hosts’

Zombie flies have been found in the Western United States and Canada. “Not even scientists are sure exactly where they came from, and that’s another thing that’s kind of weird about them,” Barrow said.

This sighting in Collinsville is “the most Southeast that they have been found,” Barrow said. They only have been known about in the United States for a few decades.

“What I find concerning is not only are honeybees part of their prey, but so are bumblebees and paper wasps,” Barrow said. “If they get ahold of native pollinators as well, then it just kind of spreads itself. Not only do we lose honeybees but we lose native pollinators. We have quite a bit of hosts that are out there.”

Beekeepers should “keep a vigilant scouting routine on honeybees and note any unusual behavior,” she advised. It should be reported immediately to her or to the state apiarist at Virginia Tech or, as Berry did, to ZomBee Watch.

“I hope more beekeepers will get involved and send their samples,” Berry said. “I’m not a biologist or scientist of any sort, but we know this is an issue. We don’t know how big an issue it’s going to be. … I don’t feel like this thing is only here in Collinsville.”

He said conditions where he lives just make it easier to spot a problem: His hives are close to his garage and house, and the outside light makes night-flying zombie bees easy to spot. “Most beekeepers are in rural areas” where it would be harder to notice nighttime flying by bees.

‘A recent phenomenon’

“One question I don’t know if anyone knows the answer to is why is this a recent phenomenon? Has this species of fly only recently started attacking honey bees?” Keiper said.

“Think about the fact that honey bees were only brought to the US less than 400 years ago,” he continued. “That’s a relatively short time frame from an ecological and evolutionary standpoint. So yes – in my estimation this jump from wasps and bees (such as bumble bees) to honey bees as a host could have occurred in recent years and is now only becoming widespread enough to be noticed.”

So far, Berry’s hives “seem to be pretty good,” he said. He still tests 10 or 15 dead bees at a time, and hasn’t seen more larve.

“Bees are dying every day. It’s when I see en masse – 20 or 30 at a time – is when I look at it more closely,” he said.

The consensus among beekeepers “is if you have a strong colony, it will keep it in check,” Berry said. “Bees are hygienic. If a bee dies in the hive, they (other bees) pull it out.” That helps keep the parasite from getting a stronghold on the hive.

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