|Typically the host survives the bot fly. Not this time.|
Sunday, September 21, 2014
Bot Flies in Maine
Note: This program first aired on September 20, 2014.
All of this got turned on its head after a conversation I
had last week with Susan Hayward, naturalist extrordinaire and a founding
co-director of the Maine Master Naturalist Program. She was commenting on my
recent program about horn worms (aka hawk moth larvae) and the curse of the
naturalist to be simultaneously fascinated and repulsed by something. She
shared her own experience of recently watching a bot fly larva emerge from a
meadow vole. Wait, what?? A bot fly larva? We have bot flies in Maine?
There are so many reasons I am grateful to live in Maine. One of those reasons is the list of things I just don’t need to worry about, like poisonous snakes. The historic and even then very rare reports of timber rattlers in the far western mountains never cross my mind when I am in the woods. Also on that list are poisonous spiders, both poisonous species that are occasionally found here are not native. Brown Recluses and Black Widow spiders make their way into Maine using the time honored tradition of non native species everywhere, they let us transport them, in this case on things like bunches of bananas or grapes, or shipments of used furniture. Our biting insects, though fierce, are typically not deadly. I don’t have to worry about getting malaria or dengue fever from a mosquito bite. Our long winters keep all kinds of tropical maladies and pests from becoming issues here in Maine.
Bot flies are a pest that I typically associate with warmer places. The fly lays an egg that ends up contacting your skin, and the egg hatches stimulated by the heat of your body. The tiny larva then burrows below your skin, into your body and sets up shop. It feeds on your flesh and breaths through a hole it maintains at the surface of your skin. It gets big. Once it is developed enough, it crawls out of your body, drops to the ground and pupates in the soil. Everything about this is simultaneously fascinating and revolting, but it was never something I thought I had to worry about here in Maine.
It is apparently quite rare but not unheard of for humans to get parasitized by bot fly larvae in this part of the world, but if you need something to worry about, feel free. I am going to put the rodent parasitizing bot flies in the same box in my brain as timber rattlers and brown recluse spiders, the one labeled “cool, possible, but not worth worrying about”. I encourage you to do the same. And one more thing, if you want to know more about bot flies, my advice is, don’t google this while you are eating.
Photos courtesy of Susan Hayward.
UMaine cooperative Extension site: http://umaine.edu/home-and-garden-ipm/frequent-specimens/frequentspiders/
Bug Guide to the rescue: http://bugguide.net/node/view/551729/bgpage
Images of Rodent and Rabbit adult bot flies http://bugguide.net/node/view/53511/bgpage
Rodent Bot fly fact sheet: http://bspm.agsci.colostate.edu/files/2013/03/Rodent-Bots.pdf