I was re-baiting a rat trap in a black plastic box(the box is open at both ends to allow entrance to the rodents)in the back yard and found a dozen or so of these inside the box (but not on the trap). There was also an adult earwig in the box. The cocoons (?) are soft/flexible and covered with sand. The larva occasionally sticks its head out of one end and can pull itself along on a piece of paper.