my mantis story.
My first diving trip was in the Caymans when I was 13.
I brought a 2 gallon tank to set up while I was there with
things I caught from the reef. The first day I went snorkeling off the beach and
caught a few little damsels and a really cool looking shrimp

I was really excited to have all my little critters in my vacation nano tank.
Paradise did not last long. The next day I checked the tank and all the fish
had disappeared, only the shrimp was left. I was pretty sure the maids did not
remove my fish, so I blamed the shrimp, which upon closer examination looked
really mean. I took the shrimp back to the beach and let him go. He was probably very happy at that point having a huge meal basically handed to him. the rest of the trip I collected just fish.
From what I remember the shrimp was pretty big, so it must have been a full grown mean and nasty mantis.