Thank you for all of your answers. That does sound like an interesting science class Kris, praying mantises are fascinating. I saw one once on holiday. It was on our porch and it was huge!
Davenmidtown, thanks for the interesting information. I didn't know anything about them being invasive. If we get them I will have to be very careful of how I dispose of their droppings. ... And I love the idea of having hermit crabs for pets!
Thank you for your comment Anil and Honey. Pets can be good company and we grow fond of them.