I found these “crater” looking things in the attic’s insulation today. In the center of the crater there is a small hole. There were probably about 25-30 of these throughout the attic. My guess is some form of insect burrowing. I also thought, because of the discoloration, it could be due to water dropping. However, there is no sign of water penetration throughout the attic. I have never seen these before and was hoping someone else has. Thanks in advance. \
I did not see any rusty nails up there but looking at that last photo there does appear to be a rusty nail on the top, so there very well could of been. The rusty discoloration would make sense to condensation forming on the nails.