Bugs in my wheat berries??

We have a local farmers market that sells whole wheat berries for grinding. I purchase them every few months for baking. I have found on more than one occasion that there are small black living bugs in the container before I even open it if I don't use the berries soon enough. What are they? How do they get into a sealed container? If I don't see them and I use the berries right away are they still dormant in there? Am I eating them unknowingly? Totally freaked out