One of the most common pests in honey bee hives are sweet ants.
Most beekeepers see them under the cover and on top of the inner cover. Sometimes they are even under the tin on the cover. I have seen many beekeepers go a bit overboard trying to keep ants out of a hive. In our area of SW Missouri ants hold no threat to a colony of bees. Mostly they are just looking for a warm dry home and maybe an occasional bit of sweet food usually from the beekeeper. They do get into the hives on very weak hives but in most cases they are still not the problem or even a threat. The video below discusses the sweet ants in more detail and possible solutions like cinnamon.