This Mud Dauber Wasp is building a nest to lay its eggs in. It will fill each chamber with spiders that it has paralyzed with its sting. Once the chamber has enough spiders, the Mud Dauber will lay one egg in the chamber, and then seal it. When the egg hatches, the larva will have a large supply of fresh, live spiders to eat.
Arachnologists, scientists that study spiders, collect Mud Dauber nests as a way to quickly and easily collect a wide variety of spiders from the area. This lets them survey the local spiders, and even discover new species, without having to crawl through the grass for days searching for them.