We were playing around in the creek behind our house a few days ago. Looking up at the concrete supports for a bridge, we found the curious markings you see here. They are about an inch across, and take the form of white ovals with feathery lines extending out from them. They look for all the world like they are drawn with Liquid Paper. Inside the ovals there is a raised ribbed texture stuck firmly to the concrete.
I explained to my six year old son that they are messages written by aliens.
I do, however, admit that there is some small chance that they were made by (terrestrial) insects.
Does anybody know what kind of insect does this, and what they’re up to?