cobwebs seem to be eating my window screen. I cannot see any insects. What is it?

Answer 1

cobwebs/spiderwebs are protein based, so there's no way it can eat through metal or plastic or whatever your screens are made of. most likely it's some insect like an ant or beetle, insects that can chew basically, that are eating through your screen. just spray some bug spray on their and your problems should cease.

Answer 2

it could be seed fluff from plants or trees in your neighbourhood. However, spiders can hide in a crack so tiny that you can't see it and some spiders are very small.