Bug Habitat: Georgia, USA

I was searching for the source of some ants in my kitchen and decided to remove a couple outlet covers to see if they were coming from one of them. The 1st one I popped open had the strangest stuff inside: a ton of little brown and black balls (along with the carcasses of a couple insect that appear to be very old). The balls that appear to be floating are actually caught in cobwebs.

I don't think this was done by a mouse or anything similar as the only entrances into that enclosure are about the diameter of my pinkie.

The outlet 18" away had nothing in it.

Any idea where this stuff came from or what it is?

Thanks,
Sean