We have a variety of stinging insects in this neck of the woods. We have paper wasps that build communal nests made of a paper like material. The red paper wasps are my least favorite - they have a sting like the kick of a mule and I happen to be allergic. Fortunately not an allergy that impacts my breathing but I do get large red welts with read streaks moving up my body from the sting. These qualify as the most dangerous to me. Among the least dangerous to me, or to anyone else are the mud daubers.
Mud daubers are about an inch long and all black. They have a characteristic tiny waist of a wasp and they build their nests out of mud. They are mostly solitary and put one egg in each mud nest along with a variety of spiders they have incapacitated with their venom. They do have stingers but only seldom sting people.
I bring all this up because I discovered some mud dauber nests on the walls of the main aisleway of my barn. Now, they build nests all over my barn, usually behind the hay or in dark corners or high up in the rafters. This is the first time I've seen mud dauber nests so out in public. I'm glad to know they are reducing the number of spiders in the barn by giving their soon to hatch young'uns something tasty to eat. I'm also very glad that they don't generally sting.