I don't support the killing of living things, but our office was being seriously overrun by thousands of ants. I had to put some Terro out and cull the invading army. My office-mate joked about readying the tiny ant coffins and before he came in, I printed one of these tiny ABS plastic ant coffins and put it on his desk. I suppose it could be scaled up to carry a larger creature, but I leave that (and the addition of a cover) to you.
I opened this STL in ReplicatorG, clicked Build and our MB Replicator spit it out. That's it. (I've seen it show up with the opening down in ReplicatorG for some reason, so just make sure it's facing the right direction before you print it)