Rodent Bot Fly

Please help me Bugman. .
I caught this fly, however, this is the biggest fly I have ever seen!! Its over an inch long and its so fat it cant fly, maybe ready to give birth to a small child or something? I thought it was a bee of some kind at first but it resembles more of a fly than anything. The pictures make it look small but this thing has some serious girth to it. Let me know what I have please. I’m really boggled and amused!! Thanks,

Hi R.E.,
This is some species of Bot Fly in the family Oestridae. They are also called Warble Flies. They are host specific. Some are parasitic on rodents like squirrels and rabbits, and there is a human Bot Fly in the tropics. The maggots burrow into the skin and cause a large bump with an open sore known as a warble. Not a pretty picture. Sorry we can’t identify the species. Perhaps Eric Eaton can. Here is what Eric wrote: “The bot fly is a rodent or rabbit bot in the genus Cuterebra. The adults do not feed. In fact, tey have no mouthparts! They live briefly, fueled by fat stored in the larval stage. Male bots practice ‘hilltopping,’ whereby they stake out a perch on a promontory, the better to intercept females flying below. These are not commonly-encountered flies, despite their relative abundance.”

2 thoughts on “Rodent Bot Fly”

  1. Currently, I live in rural NW Oregon, about a half hour outside of Astoria, and we have a chipmunk with five botfly larvae under its skin. Recently, a new species of very large squirrel arrived. This is a type we have never seen before. It’s 4-5 times LARGER than any of the other native squirrel species and within days it had chased out all the other squirrels and most of the chipmunks. Turns out, this new squirrel species is from the Yucatan peninsula in Mexico and according to a few websites, it migrated up here because of A) it’s too hot on the Yucatan, and B) the forest fires in CA. I’m wondering if there is some kind of connection and who should we report this botfly infestation to? Is there still someone studying this? We’ve had some very hot days up here and I worry about our other animals and other local wildlife.
    Thank you, Eva in Oregon

  2. Hello, I am also in Oregon (central coast range, just inland from Newport). We found a chipmunk with two botfly larvae that emerged from it’s abdomen shortly after it’s death. I’ve never seen anything like this before, it’s the most disgusting thing I’ve ever seen. Brown, large, chewed it’s way out. 🤮 I have pics and video. Hope this isn’t a invasive or common thing, hope my dog doesn’t get it. She’s squirrelin’ all the time… Nightmarish!!


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