Yes. You can FedEx spiders. USPS won't take them. They will take ladybugs and mantis cases and cockroaches though. (Gardening supplies and pet supplies - I've not *actually* had to mail any of these to 3rd party vendors. Yet.)
@bastlynn Also USPS; chickens. I've never ordered any before but I picked some up for a neighboring farm once years ago. Box full of peeps.