Another use for old bricks

It is wonderful how quickly a pile of bricks gets colonised. I suppose when the pile is six bricks deep and twenty bricks high, low down at the back it is always dark and cool and moist. Ideal evidently for yellow slugs (Limax flavus) , of which we found dozens when we took the pile down. They'd even laid eggs (I own up to some rearrangement to make a convenient picture). They are entirely beneficial, just eating rotting stuff and so helping to speed up the cycle, and thus common inhabitants of compost bins.

But it beats me what they find to eat in a pile of bricks.