Finding its marks to be on the move, the bug backed away and collapsed the northen entrance of its tunnel. Moving backwards and turning around, the bug picked up its bag, then left through the southern exit, collapsing that tunnel as well. Knowing it would be a long time until nightfall, and not wanting to wait all that time while following its mark, the bug devised a plan.
Moving behind the building, the bug waited until its mark had entered the other building, and until the coat was clear, then sprinted towards the other building, although it didn't approach its front door or any windows, instead stopping at the corner.
There, it hung the bag from its tail and dug a tunnel downwards, again using both its hands and forelegs. Once it went deep enough, it covered the entance up a little and continued digging. Still being able to navigate well enough underground, the bug began digging towards the front door of the building its mark entered, then began digging a steep tunnel downwards and away from the door. Once it dug deep enough, the bug moved back, and made a small opening to the surface.
With this done, the bug began slowly widening the would-be entrance to the tunnel, spinning webbing near the surface to make a trap door, covered by the layer of soil. With its trap in place, the bug spun webbing to its trap door to alow it to open it once it smelled its mark again, then laid in wait, feeling for vibrations when people moved over the trap door, and smelling for the scent of its mark.