Chipmunk Bot Flies WA

I have a large ‘colony’ of Townsend’s Chipmunks that hang around my property in Island County WA, I have bird feeders up and they clean up the spilled/dropped seeds under the feeder and also greatly enjoy the snowberry bushes and native plants near the woods. Today I noticed at least 2 possibly 3 of the chipmunks have single botfly warbles located behind their arms. I didnt think that botflies were that big of a problem in WA state as I have never really seen them before this.

Should I worry about this? Do botflies kill their hosts and how do they spread? Do they spread through chipmunk contact? Should I consider taking the bird feeders down for a little while to keep inter-chipmunk contact to a minimum?

I dont want the ‘chippies’ to be negatively affected by this, apparently botfly warbles are mainly a summertime thing. I can post some observations of the warbles if anyone is interested aswell.

Your feeders can’t really affect them, even if imago will gather around they’d find hosts anyway, larvae can’t go from one host to another, it can’t go anywhere after it found the spot to bury in host’s body (some migrate under the skin, but still, not out of it), they can’t kill it directly (but huge infestation definitely takes a toll on the host and things can happen because there’s an open wound), they will be out of host when it’s time to pupate.


Agree with @marina_gorbunova - bot flies are larvae from eggs laid on the host (or even an intermediate host). Inter-chipmunk contact is not the problem. The flies may be attracted by more chipmunks, so reducing the numbers may help. But they don’t kill the host unless there are huge numbers.

As someone who recently had a bot fly, I can attest that they do not kill their host :) Human bot flies are spread by flies, mosquitoes, and ticks (most commonly mosquitoes). I’m not sure if rodent bot flies are spread the same way, but probably so.

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I’m used to seeing “bot fly” as a compound word, so the space in the title was throwing me off. I assumed you must have seen a chipmunk-shaped drone.


IIRC, rodent botflies (Cuterebra sp.) simply lay eggs near a potential host’s burrow and the hatchling maggots crawl around in search of a host to cling to like ticks.

Thanks y’all, I’m relieved to hear that this isn’t too big of a thing to worry about. I posted the one I was most concerned about here warning as it is a nasty warble. Its surprising to hear that the warbles aren’t too bad considering how awful they look.

Wow… you are right; that certainly does look awful. I’m relieved if this is something they weather relatively easily.

Rodent botflies are huge compared to the size of their host, at least in small ones like mice and chipmunks. It’d be like having a botfly larva the size of a small rabbit on a human.

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