Ground nesting wasps or hornet
these hornets/wasps have dug holes between the brick on my patio. they are bringing grass hopper to place in there pits. I have included three pictures. Because they seem to be solitary hjornets I have left them alone on the assumption that they won't sting. :)
Lane County Oregon hornets
These may be ground-nesting (solitary) bees rather than wasps. In either case they won't swarm like yellowjackets but all bees and wasps will sting if handled. If you've seen them placing grasshoppers in the nest then they may in fact be wasps since wasps are predators, bees gather pollen and nectar (even ground-nest bees).