Thanks, Elaine! I just opened the container to check on everyone. I think I found a fifth cat. It's right below what looks like a hatched egg. I'm too tired to get the microscope back out right now.
Okay, I just touched it with my fingernail and it moved around. Definitely a caterpillar. I don't think it just hatched, though. Even as small as it is, it couldn't fit in the egg.
I need to get new lenses for my glasses, but I'm thinking I should wait until after I raise these guys so I can just mess up my eyes as much as possible first.