Posted: 26/05/2013 at 20:45
Mining bees, do exactly that. they dig out a chamber and lay an egg and raise one offspring in that chamber. We have hundreds of them in the garden and very welcome they are too, even i it does mean we have to hand weed the cobbled paths as they nest in between the cobbles.
Frequemtly asked question at this time of year is about the tiny mounds of soil people find in their lawns. Not worms as sometime suggested, but these mining bees.