So I found some winged "ants" on my roof. My roof and crawl spaces have vents with 1/4 inch wire mesh, very easy for such "ants" to get into.
Of course, they were not ants, they were swarmer termites. In this case they came from outside the house. And I happen to know they were drywoods. That said:
What size mesh is needed to keep out swarmers, without blocking too much ventillation? If you answer, what's your source for the information?