Bull Bees are enemies seen in Phoenotopia that are only found in Sunflower Road. Initially, Bull Bees fly around set routes and will make no attempt to hurt Gale, though they will passively damage her when touched. They are weak enemies and can be killed by any weapon in one hit.
However, if the player kills a Bull Bee, all other Bull Bees onscreen at the time will get enraged (turning red to indicate their anger) and chase after Gale, which is why it's usually a better idea to just try and avoid them all together. Otherwise, the player will likely get stuck in an endless cycle of killing off Bull Bees in self-defense only to agitate even more of them due to the large number of Bees there are in Sunflower Road.