A small bottle trap would probably work. Cut the top off a bottle, invert it, shove it back into the tube, stuff meaty food into it, and set it on its side for things to crawl into. You're just about guaranteed to catch a few worms at the very least, and if the little guy can climb into the trap, you'll get him. You can also try just catching him by hand, he looks small enough to not do any damage to you.
Do you know where he's hiding?
If he is a box, and he sure looks like one, he shouldn't be a problem until he gets at least an inch across. What is he now, maybe half that? Less?