Ive had my undulate for about a year and a half, and she is just now getting to be around 4 inches... When i got her she was about 2 inches, so in a year, I doubt a 1 inch undulate will get hat back because they are such slow growers... I have full confidence that my undulate would be able to take out and holds its own to just about anything...HOWEVER, The real question is where these two would meet??? If the trigger was just dropped in the tank, and the mantis had the homefield advantage I think the mantis would, with little doubt, have the first strike. However, every one lived in a 55 or 75 gal with a divider and both were established, then one day the divider was pulled out, such that it was more even territory, the odds would be more interesting. I did read of a pair of large mantids taking out 4 queen triggers in a night at a lfs though...
I also think an eel would be an interesting battle as well....
But for the trigger, My money is still on the O. Scyllarus.