I see some of them every summer because the cats can see them fine and are not actually chasing invisible objects. Some of these little guys are so very small they can fit through the mesh of the screen, though they never seem very happy about actually being in the house once they've done that.

I'm also forever looking at a bee or dragonfly on a flower and seeing that there are half a dozen very small beetles or aphids or flies or mites hanging out nearby.

P.