On Mon, 5 Sep 2011 07:46:40 -0700 (PDT), alec green
wrote:

There are no obvious signs of damp which I believe they like. Is
there anything available to track their entry point?

You might try a fine coating of dust over a couple of square feet.
How fine it would have to be, I don't know, as I've no idea what kind
of foot pressure/dragging woodlice have.
Failing that, just nuke'em with insect killer.