ZomBee Watch - flight of the living dead

It may sound like the title of a ‘bee’ movie, but the threat posed to North American honey bee hives by parasitic zombie flies could potentially be very serious, and a citizen science project based in California is aiming to determine whether or not this is the case.

Apocephalus borealis, otherwise known as the zombie fly, deposits its eggs within the body of a live honey bee. The eggs then hatch into larval maggots which devour the honey bee from the inside, causing the bee to abandon the hive in the middle of the night in search of bright lights. Infected honey bees become disoriented and erratic before eventually dying and hatching as many as 15 maggots.

Dr John Hafernik, from the Department of Biology at San Francisco State University (SF State), was first to observe A. borealis parasitizing honey bees back in 2008. He and his colleagues initiated the ZomBee Watch project with the aim of finding out just how widespread the parasitism is, and whether zombie flies are major actors in honey bee hive loss or simply perform a supporting role. 

The team also asks volunteer citizen scientists to help determine how often honey bees leave their hives at night for other reasons. To test for the presence of zombie flies, it is necessary only to collect stranded honey bees in a container and wait to see if maggots exit. These then pupate before the next generation of flies emerges, within two to four weeks.

Dr Hafernik took the time to answer some of ScienceOmega.com’s questions about ZomBee Watch; how it came about, how it operates, and how citizen science is helping achieve the project’s goals…

When and how did you first discover that Apocephalus borealis was parasitizing honey bees?
I first discovered by accident that A. borealis was parasitizing honey bees in late 2008. I noticed a large number of honey bees acting strangely in front of Hensill Hall, the building I work in on the SF State campus. I had brought back a live mantis from an entomology class field trip, so my first thought was, ‘mantis food’. The mantis was hungry and needed feeding. Each day I would capture stranded honey bees in a vial and feed them to the mantis.

One day, rather than feeding the mantis, I went to my office first, left the vial on my desk and forgot about it. A week or so later I noticed the vial was filled with small brown fly pupae. I realised that this could be important and began putting a team together to investigate.

Ultimately the team included SF State graduate students Andrew Core, Jonathan Ivers and Christopher Quock; undergraduate students Seraphina DeNault and Travis Siapno; my colleagues Dr Christopher D Smith of SF State; Dr Brian Brown of the Natural History Museum of LA County and Dr Joseph DeRisi of the University of California San Francisco (UCSF) and his student Charles Runckel. We published the results of our multi-year study last January.

How big a threat do zombie flies pose to North American honey bee populations?
At this point we don’t know how big a threat the fly poses to honey bee health. The fly has infection rates in bumblebees – one of its native hosts – as high as 80 per cent, suggesting that it could have a large impact on honey bees. So far the highest rate we have observed in honey bee foragers is in the 20 to 25 per cent range. Rates are usually lower; in the five to ten per cent range. This varies with time of year. Honey bees attracted to lights at night have infection rates as high as 90 per cent.


How is citizen science helping you and your colleagues in your studies of zombie fly parasitism of honey bees?
My colleagues and I started ZomBee Watch because we knew that the fly was known across much of North America and might be infecting honey bees throughout the United States and Canada. To find out if it is, we decided to enlist citizen scientists around the country to determine the geographic extent of honey bee parasitism by the fly. We are gratified that our vision of crowd-sourcing discovery is working.

How does the project operate? What kinds of observation are required?
Citizen scientists are asked to look for bees acting strangely under porch lights and streetlights. If they are a beekeeper or live near a beehive we provide instructions on how to construct DIY light traps to capture bees leaving their hives at night. We provide a tutorial that shows them how to isolate bees in containers and check them for the emergence of fly maggots and the formation of pupae near infected bees.

They report their findings by visiting ZombeeWatch.org, registering, and uploading photos and numerical information. We are especially interested in receiving more submissions from the eastern US, the Midwest and Canada. We are interested not only in positive records of parasitism of honey bees by A. borealis, but also in negative findings. 

The response to the ZomBee Watch website has been excellent. Yesterday we set a new record for visitors and we may break that record today. We are well on our way to reaching our goal of an army of committed citizen scientists using their eyes and intellects to make new discoveries. It’s possible that while they are helping to determine the distribution of honey bee parasitism by A. borealis, they may also discover new things about honey bees.

What have you learned so far about the behaviour of the zombie flies and their geographical distribution?
Citizen scientists have already made significant contributions discovering parasitized honey bees in two new states: Oregon and Washington. The new records from Oregon and Washington are important.  They show that parasitism of honey bees by A. borealis is not limited to the San Francisco Bay Area, but is probably widespread along the West Coast. This raises the spectre that A. borealis is contributing to hive losses over a wide area. The new records are also a great example of the power of citizen scientists to make important contributions to studies of honey bees and pollinator health as well as other areas of science.


Find out more about the ZomBee Watch team members making the project possible.