The empty Organ Pipe Mud Dauber Wasp nest popped off the wall with relatively little damage:
The open cells on the back side show the wasps don’t waste any effort on putting mud where it’s not needed:
Cracking it in half shows the rugged walls between the cell columns:
Several cells contained three or four (thoroughly dead!) spiders apiece, evidently the result of un-hatched eggs:
Each successful cell contained a brittle capsule wrapped in a thin cocoon, surrounded by fragments of what used to be spiders, with an exit hole chewed in the side:
I regret not weighing the whole affair, as all that mud represents an astonishing amount of heavy hauling and careful work by one or two little wasps!