When someone is said to be unruly it means that controlling the person is a difficult task because such people do not like nor will they obey rules.
Another word for this is wild. A wild person is one who acts as if they cannot follow the rules of civilized society and as such can act in an unacceptable manner which is much like the word unruly. The bees in question are therefore being said to be wild which makes sense because they are wild insects afterall.
