Hey folks, I'm looking to get a couple of invertebrates for my classroom so my animal behavior students have interesting non-reptile critters to watch and care for. I'm considering Madagascar Hissing Cockroaches and was hoping to also get some type of crab. I've been looking into the "moon crabs" we see at reptile shows in the area and now I see that they can also be called Halloween crabs, but that this may be an entirely different species.

Can anyone help me out on this, and/or point me towards some reliable info on these guys?