I have had a lot of experience with mantis hitchhikers. I had two at the same time in my LR
. One cheap trap you can try that worked for me is to take an empt 1 or 2 liter container of soda. Cut it in half. Take the piece with the top and shove it, top first, into the other piece. This makes a cheap little trap for the mantis. Now place a piece of shrimp or any meaty fish food in the trap and then submerge it in a place that you have spotted him. It took me about a week to get the little bugger, but it worked out pretty good. Unfortunately I caught some other fish in there aws well so I had to reset the trap a couple of times. Good luck. My second mantis cracked my all glass tank and I broke that down in record time.