Paper towels make the best substrate for keeping delicate invertebrates safe during shipping.
It is up to the person doing the packaging to make sure the creatures are able to survive any trip / shipping.
Steps:
Use a deli-cup or container that is 1-3 inches bigger than the invertebrate you are packing.
Place some loosely wadded, slightly dampened paper towels in the bottom of the container and along the sides to make a nest in the middle just large enough for the critter.
Place the creature into that nest and cover the top with more of the loosely wadded paper towels and secure the lid. This will provide cushioning in all directions to absorb the various shocks and bumps that will come.
Follow all additional shipping requirements contained in Shipping Requirements on this site.
When shipping in cold weather, use minimal moisture or completely dry paper towels.