honey bee threats parasites

Zombees arrive in Washington

It’s ironic that just two weeks ago I signed up with ZombeeWatch.org, intending to set up a light trap and send my results, positive or negative,  into the database. I just had a feeling the parasite would be here because we are not that far from California and Oregon, places with known Zombees. Sure enough, an article in today’s Seattle Times reports the first confirmed case of Zombees in Washington, in a town about 55 miles north of where I live.

I first wrote about the parasitic fly, Apocephalus borealis, back in January (A fly in the hive causes bees to flee) but after that I didn’t hear much about them until one of my readers on the east coast wrote last month, asking if there was anything thing else that would cause honey bees to be attracted to light. While looking for an answer, I got interested in the phorid flies again and joined ZombeeWatch.

I have no particular reason to think I have a problem with the flies, but I thought it would be interesting to set up a trap. I don’t normally run exterior lights at night so unless I deliberately set up a light trap, I would probably never notice bees at a light source.

My hunch—at that’s all it is—is that the parasitic flies are widespread and much more common that anyone suspects. Since they are a native species that preys on bumble bees and certain wasps, I suspect they more-or-less follow the distribution of those species. The big unknown is whether the flies have always affected honey bees or if they have recently evolved to parasitize them. And, of course, if it is a recent change, how bad will it get?

The article about the first Washington case can be found here: “State’s first case of ‘zombie bees’ reported in Kent.” You can join ZombeeWatch.org—or just learn more about the so-called scuttle flies—on their website.

If you are unfamiliar with this parasite, the small adult fly lands on the back of a bee and injects its ovipositor into the bee’s abdomen. It lays eggs there which eventually hatch into larvae and feed on the inside of the bee. The bees become increasingly agitated and, at some point, become attracted to light. They fly from the hive at night and hover around a light source until they die. After the bees die, the larvae crawl from the bee’s body and pupate into something the size and shape of a grain of rice. New adult flies emerge from the pupae several weeks later.


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  • I invited Research Professor John Hafernik with SFSU who discovered the fly to come and speak at our SF Beekeepers Association in January. He gave a very interesting talk. The bottom line is that it is more widespread than initially thought and it’s just another pest that plagues our bees along with mites and SHB.

  • I am kind of curious about something. If the affected bees leave the hive and seek a light bulb in the night, should we not be able to trap them to keep the numbers down. Can this trapping be successful enough to matter?

    • Aram,

      What an intriguing idea! From what I understand, you can get a number of larvae from one bee, so if you could trap a large proportion of bees you should be able to slow the increase of adult flies. And if they separate themselves from the hive like that . . . well, that’s very convenient.

      I suppose it would depend on how reliably the infected adults are attracted to light. Do all affected adults go to light or maybe only a percentage? Also, is it the light they are seeking or is it the heat? It would certainly be worth some inquiry, especially if the flies turn out to be a big problem. There’s a lot we don’t know.