Answer:
They use their sense of smell..
Step-by-step explanation:
Bees know what the bees within their hive smell like.
Intruders will smell different and they will sting the intruder.
(Interesting fact: When honey bees sting, they release pheromones that stir up nearby bees. One stinging bee can turn into hundreds or even thousands of stinging bees in just a short time.)