How can we determine what kind of ants we have and how to get rid of them?

We have some ants that are small and black that seem to be living in our window sash or behind our walls. Every once and awhile they will poke their head out of a hole at the top of one window in our pool enclosure and drop some crumb of unknow origin and it piles up at the bottom of the window. We have tried ant traps, boric acid and sprays to no avail. Short of calling a professional what can we do? What kind of ants are they and what are those crumbs piling up?