WARNING: If you are squeamish about bugs, flies, fungus, or creepy crawly things, you might want to skip this post.
I spent a little time in my garden today and was surprised to find a large number of dead insects clinging to the undersides of leaves, on flowers, and even clustered on a metal wire I use to mark the edge of my vegetable garden. They are in the back yard and the side yard. I am a novice gardener, so I don't always know what is normal and what is unusual. I'm leaning toward this being unusual.
It took me a while to figure out what insect I was looking at. When I found a few that still had their wings barely attached, I realized they were all ordinary bottle flies.
How do bottle flies normally die? Wouldn't they be like houseflies, curling up in a corner? These dead flies all have a tight grip on the leaves and wire. That can't be normal. It reminds me of the parasite that turns honeybees into zombies or, even more so, the fungus that does the same thing to ants.
Some of the flies appear to be slowly expanding, their exoskeleton cracking open. At least, I think that's what's happening. I'm not equipped or willing to start a dissection.
I tried doing a search for parasites that kill blowflies or bottle flies, and all I came up with was information about their larvae being parasites that harm birds. Then I remembered learning about a fungus turning ants into zombies, forcing them to climb upwards, then cling onto a leaf or branch with a death grip, allowing the fungus to grow inside the ant, then disperse its spores from the corpse.
As soon as I Googled for blowfly fungus, I found a photo from 2008 of a blowfly killed by fungus in Massachusetts. Mystery solved!
Further research suggests that the fungus is possibly Entomophthora muscae (or a related fungus).
For more on fungi turning flies into zombies, read
Donegal Wildlife blog (fungi in Ireland in 2008)
Fly-Killing Fungus photo (2006, no location)
New Zealand lab experiments to create zombie-making fungus in 2007 (okay, I'm sensationalizing a little; but it's so much like in the movies! Scientists develop fungus that kills flies--what happens next? Does the fungus start to turn humans into zombies? Stay tuned, and watch out for climbers!)
Biopesticide Evaluation, 2009
Dead blowfly in Louisiana, 2009