Zombifying flies and their honeybee hosts

Honey bees around the world have been dying at alarming rates, creating widespread concern and bafflement among both public and scientific communities. In the United States, symptoms of these impending declines are collectively referred to as Colony Collapse Disorder, or "CCD". CCD is primarily characterized by hive abandonment, where no or few honeybees are present in a hive even though a live queen remains.  While many factors contribute to bee declines such as mites, viruses, bacteria, fungi, and pesticides, Dr. John Hafernik, a biology professor at San Francisco State University, discovered another contender by accident: the parasitoid fly Apocephalus borealis. With the help of colleagues and his graduate student Andrew Core (the lead author), the team worked to figure out this mysterious host-parasite relationship. Recently, their fascinating findings were published in pLoS one.


It turns out that female A. borealis flies will locate honeybee hosts and land on them, depositing their eggs or "ovipositing" them into the bee's abdomen. The fly larvae develop inside of the bee and approximately seven days later they emerge, killing the bee in the process. This is very reminiscent of the movie "Aliens" isn't it?

The parasitoid fly and it's honeybee host. A) An adult female Apocephalus borealis fly. B) A female A. borealis fly deposits eggs into the abdomen of a honeybee (note how small the fly is). C) Two A. borealis fly larvae exiting the host. Photo credit: Core et al. 2012.

The even more curious thing is that the parasitized bees exhibit very unusual behavior before fully succumbing to the parasites. They abandon their hives at night; healthy bees usually leave their hives during the day to forage. They wander about aimlessly in circles, appearing disoriented and unable to properly balance. Moreover, the bees become attracted to light at nighttime. Core and colleagues suggest that the parasites may manipulate the light sensitivity or circadian rhythm of their hosts in some way, but more work is needed to fully investigate these possibilities.


The troubling realization from all of this is that honeybees usually occur in high densities, and colonies are often found in close proximity to each other. These conditions could make it very easy for fly populations to boom and further decimate honeybee populations that are already in decline. Honeybees are crucial for the pollination of many plants and agriculturally important crops, and for the production of their highly prized honey.  Research conducted by groups such as Core and colleagues is vital to the preservation of these important insects.

Find out more about colony collapse disorder:

USDA Agricultural Research Service

http://www.ars.usda.gov/News/docs.htm?docid=15572

Environmental Protection Agency:
http://www.epa.gov/pesticides/about/intheworks/honeybee.htm


Bromenshank et al. 2010:
http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0013181