Do you have an open garden? I'm wonder whether it could possibly be foxes or badgers. Both of them have a habit of foraging for beetles and insects (particularly badgers whose main diet is worms). If you have any flower beds nearby look to see if there are any fresh patches of earth which look as if they've been disturbed. Although if it is badgers, why they should gather everything in piles is a mystery to me. If you have any small burrow holes nearby, the other possibility could be rats who are quite capable of digging and tunnelling.