A good way to ship larvae and/or eggs is to use the cheap Gladware containers.
Cut most of the top of the lid away with an exacto or razor blade, leaving about 1/2" to an inch remaining. Just cut out a big square on the top lid. Next, use your glue gun and a piece of tulle netting or other netting but with tiny holes! Glue the netting to the lid so that the hole you cut out is now covered with netting. Make sure that there aren't any holes or places the larvae can get out of or get stuck in! Put a layer of paper towel in the bottom. Put in plenty of foodplant with the larvae. Stack these boxes into a shipping box filling the spaces in with packing peanuts or crumpled up newspaper. Wrap up a couple of polar packs in paper toweling and place inside the box sort of close by to the larvae Gladware containers.
This will work well for shipping larvae and eggs. They need to go out for overnight delivery.