We found a bunch of these in our narrow (but fairly deep and wide) garden bed. It’s a sort of concrete tub, a long (6m), 30cm wide, 50cm deep garden bed situation. When we moved in it was like dry, dusty concrete. So we mixed in some poo, put down a good, solid layer of paper and then mulched it up the wazoo.
Today we dug up a bit to put some plants in, and found a bunch of these fatties. They looked very healthy. On the one hand, it’s good that there’s life in there (and the dirt looked much, much better), but on the other: will these bastards eat the roots of our new baby plants?