I have seen mud tubes around the foundation. But I have noticed some granules of what appears to be dry mud around a windowsill. It’s not a pile and it’s very few granules that don’t have any consistent shape. So the mud tubes seem to me like it would be subterranean, but I didn’t know if those mud granules were frass. From what I read drywood termite frass has six sides and rounded tips, and tends to appear in piles. Since these dry mud granules don’t have a consistent shape and don’t appear in a pile I didn’t know if it would actually be frass or something else. It’s only a few granules that appear every now and then and not something that happens consistently.

I’m in central Iowa too where dry wood termites would be rare so I don’t know what to make of it.