You have tent caterpillar. They hide in the nest during the day, and feed on the tree's leaves at night. Depending on the extent of the infestation, they can totally defoliate the tree. They will probably not kill the tree (at least not in one year). But they're certainly unsightly, and the defoliation will weaken the tree. You can spray and kill them, and / or put on a pair of gloves (because it's kind of gross) and clean out the webbed nest.

http://www2.ca.uky.edu/entomology/entfac...

Does anyone know what these bugs are? If so what are they? Are they okay for my tree or should I remove them?