Pottery on a Petiole

I was working in the vineyard doing some leaf pulling when I came upon this little mud vase that looked very much like a skilled potter made it. I thought it must be a mud dauber nest so when I went home, I looked it up on the Internet and was a little disappointed that it wasn't anything at all like what a mud dauber makes. My curiosity didn't take me any further than that cursory query that day. Flash forward.

My husband and I were working in the vineyard in our Cabernet Sauvignon doing some canopy management. In doing this, we came upon this beautiful work of pottery which was on one of our leaves. I told my husband that I had seen the same thing before on another leaf. I whipped out my cell phone and took this picture. When we went home, my husband (expert internet surfer) searched on mud pottery nest and up came oodles of images of what we took a photo of. This is the nest of a potter wasp, Eumenes fraternus.
I found more information at the Texas Aggie Horticulture Site devoted to the Potter Wasp. The potter wasp is part of the family Vespidae, subfamily Eumeninae. This creation is called a brood nest.
How does the potter wasp make this nest? They first collect water and then mix it with dry soil using their mandibles. The mud mixture is transported to the nest-making site where it is fashioned into individual pots ranging in size from 1/4" - 6/16" in diameter, or the size of a marble. The entire construction process may require hundreds of trips over several hours. Amazing!
These wasps are solitary and are beneficial because they hunt for caterpillars to paralyze and place them in the brood cell to serve as the source of food for the developing young.
Who knew that the builders of this beautiful pottery pot looking brood nests are beneficial! The vineyard is teaching us something everyday.
References:
1. Texas Aggie Horticulture Site, Potter Wasp.
2. Buckeye Yard and Garden Online, Pottery Wasp.