“That’s a beekeeper’s swarm trap. The natural reproduction of a honeybee hive is to spin off one (or more) swarms in the spring. Those swarms hang in a tree or under an eave while they send out scouts to look for a place to establish a new hive. Once a suitable place is found, they move in and start building.

These traps give them a place to move into, but the beekeeper will keep an eye on them and transfer them to a hive before they get too far along. It’s a free colony and is easier than having to remove them from someone’s shed or BBQ grill.”