Like thousands of types of insect larvae.
I am too.
There is a way to ID them. But you need very close and clear photos of both mouth and hind end.
There are insect ID groups on Facebook that have some very experienced advisors.
I think you can be pretty confident that the larvae did not come...
They were in the water?
Is the waterer on the ground?
Could be any one of a multitude of types of insect larva.
I seriously doubt they came from inside your chickens.