Sorry but they could be any number of things. Without seeing them there is no way to even get in a ballpark guess other than some sort of fly larvae.

Plus knowing where you live or at least your gardening zone would help narrow down the possibilities a little bit.

But whatever they are just dump the soil out on a tarp or plastic, spread it out and let it dry well in the sun for several days, stirring it now and then. That will kill most if not all of them as they need moisture to survive.

Dave

Thanks Dave - I'd thought that sun might do it......

If it ever stops raining, will break out the tarp.

Much appreciated.