Parasitic Fly Threatens Bees

This is an A. borealis phorid fly female, depositing eggs into a worker honey bee. Photo by Christopher Quock.

There’s a new honeybee pest in North America. It’s a native A. borealis phorid fly who lays eggs inside honeybee workers. The larva change bee behavior. This fly apparently has switched hosts from native bumble bees to the honeybee.

Could this fly be a factor in some forms of CCD?

Today on Science Friday, Ira Flatow had a segment with John Hafernik, a biology professor who discovered this fly infecting honeybees. You can download or listen to the podcast. The player is in the upper left corner of the this page.

You can read the entire research article here:

A New Threat to Honey Bees, the Parasitic Phorid Fly Apocephalus borealis


It appears to be a new kind of infestation. I doubt if strange behaving honeybees, filled with phorid fly larva, would have escaped the attention of beekeepers and bee scientists.

But who knows? Sometimes we only see what we are looking for. And it often takes someone who looks at things differently to see what others look past.

I must admit noticing small phorid fly’s inside some brood chambers a half dozen years ago. I didn’t notice any infected bees. And I doubt they were the same kind of fly. There’s a bazillion different kinds of phorid flys. But they were unique inside the hive and noticeable at the time.

Infected honeybees fly at night and are attracted to light. Several years ago, I observed honeybees buzzing the screens in our home at night. Thought it was odd at the time.  Hummm?

I hope this phored fly phenomena is a novelty! But it probably wouldn’t hurt to set up a light and check for infested bees as suggested in the podcast.


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5 responses to “Parasitic Fly Threatens Bees”

  1. ceciliag says:

    Something to think about for the spring. We are just hoping our bees last this indecisive weather pattern.. c

  2. greg breneman says:

    Depending on your winter you could have activity now, I was out side one of my hives yesterday and I saw a fly come out and just hoover there till I swatted it down but could not find it, I collected the bees that are dead for observation. So does anyone know of control methods

    • Margaret says:

      I just had some losses as well within the last few weeks. I also noticed several flies landing on the side of one hive which I found odd at the time. Any clues to look for on the dead bees or in the hive to conclude it was from these parasitic flies?

      • -bW says:

        Hi Margaret

        You could put the dead bees in a sealed jar and watch for emerging larva. I’ve never see larva emerge from dead bees in Wyoming.

        But I’m not sure what would happen in other areas. There could be other scavangers/parasites that take advantage of a dead bee’s carcus.

        Try the test mentioned in the article.


    • -bW says:

      Hi Greg

      It’s not uncommon for other critters to overwinter, in the un-occupied areas of a beehive, once the bees cluster. When the cluster breaks, the squatters flee the hive before the bees get them.

      I suspect that’s the case your fly. I don’t know the life cycle of the phorid fly, or even if it is going to be another problem. The only test, so far, is the one mentioned in the article. I suspect that more info will be available as beekeepers test their bees this spring.


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