Does Anyone Know What These Are?

Question

Hi, we have found these on the inside of our waterbutt. The body is aprox 1\\\” with a 3-4\\\” \\\”string\\\”. Some are swimming but the majority are attached to the side of our wooden water barrel. Are these an aquatic larva or are they caterpillars that have been washed in?

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Answer 1

I can't see, too clearly, from the photo, but it appears to be a rat-tailed maggot. This would be a drone/hover fly larva, if so. There are a few species, and they are beneficial.

https://entomology.ca.uky.edu/ef500