Those Mud Daubers drive me nuts.
Believe it or not the other day I had a can of wasp/hornet spray sitting out on a slatted bench in the back yard and went and picked it up....those doggone mud daubers had built a nest on the bottom of the can (the bottom is concave and was positioned above the open space between slats). I had to laugh...kind of hard to spray them when it is on the bottom of the can!
Cogar, even on airplanes here they have to block tubes when a plane is not flown daily. Those suckers will even block the air speed tubes and cause major problems (if not crashes) due to faulty air speeds!