Capturing critters for the classroom is, understandably, frowned upon. I'm more concerned for the critters than the students, not because I'm a heartless educator, but because there a few ways most of the local critters are going to inflict anything more than an adrenaline surge in the classroom
This is a slug found in my garden. While it is "humongous" as far as slugs go, just about all of my students outweigh it by at least a few stone.
This particular one is a Limax maximus, a leopard slug, but telling the kids that really tells them nothing about it. Seeing a picture of one doesn't tell them a whole lot either. Handling one changes the picture, and the slime will last well into 5th period.
And maybe mention to them that the slugs are hermaphrodites. And that they lick each other while circling end to end before mating. A lot.
Not sure my kids will remember the Krebs cycle, but slugs will take on a whole new life for them.