I haven't heard great things about mantis traps, but have heard better things about the bottle trap. Shrimp usually works fine. Also silversides, krill, clam, any meaty SW food pretty much. How long are you leaving it in there? I've heard the idea of putting it in and going for a nice long drive and it'll come out and do w/e. When you get it give it away or setup a small 5-10 gallon with some sand, a few pounds of live rock to burropw in and maybe a light if you want. Have you actually seen this mantis BTW?
Dan