5mm squares. This look like one I previously posted that was called a Pediasia. Despite there only being 8 species for North America, I've not been able to figure out which one this might be. Though it seems to not be P. trisecta (which is the only one reported from my region so far). Like the one I found previously, it was found on tide flats - presumably it had hatched out from the upper beach margin where there is grass and other plants between the beach and the forest.