The USPS has different guidelines for shipping worker honeybees versus queen bees, so make sure you know which type you will be shipping before reading on to find out more requirements.
Shipping bees with USPS as a carrier
All bees can be shipped using ground transportation. When using ground transportation, it is required that you add the extra service of Special Handling Fragile to get more careful treatment of the shipment. Only queen bees can be shipped via air transport. In both cases the shipment must be marked with a description of either the contents or delivery method on the address side to ensure proper handling. For regular honey bees the marking must be either “Live Bees”, “Surface Only”, or “Surface Mail Only”. Shipments containing queen bees must be marked with “Live Queen Bees”. Some shippers choose to make stickers with handling information like the one shown below:
Make sure that you are using a box that is intended to withstand weight to avoid the package being crushed or damaged during transport. It should also be designed to allow adequate airflow as well as keeping the contents protected from the cold or heat. As an extra level of precaution, make plans to communicate with the USPS post office that will receive the shipment of bees so that they are ready to provide timely and safe service.
These guidelines are intended for shipping bees domestically only. If international mail is being considered, check the USPS docs for live animal restrictions in the destination country.
For more detailed information refer to the official USPS docs for shipping bees:
Live animal packaging:
International mailing conditions: