J.L.
Does it look like the grass pulls up like a toupee? If yes-then it is grubs. I hear you can put a small bucket or dish with about one inch of beer on your lawn, and it should attrack the grubs to the bucket, where they drown. It is sad- as I am a lover of all animals, big and small, but they can destroy lawns. I also found that in the spring, just replace the patches with the seed/mulch mix and you should be back to good!