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It's a picture of the nest of a mud dauber wasp. These wasps get their name because they construct their nest of mud. There are several different types of mud daubers, each with a descriptive common name.
The owner of this nest is a potter wasp. It's easy to see why!
Mud daubers typically select a sheltered site to build their mud house. Some favorite sites are under eaves, porch ceilings, in a garage or shed, and in attics. The female makes many trips to get mud of the correct consistency, carrying it back to the site as tiny balls. When the nest is ready the adult wasp collects spiders, caterpillars, or beetle larvae and paralyzes them before putting them in the cell to serve as food for a "kid" (larvae) that will hatch out shortly. As a rule, the adult lays a single egg in the empty cell before provisioning it. When the wasp larva hatches it eats the supplied prey... often taking a few weeks before pupateing. The complete life cycle may last from a few weeks to more than a year! So the wasps that I have seen this spring/early summer were eggs/caterpillars last year! Wow!!!
If you find a nest and it has a round hole in it that means the wasps have hatched out. It also means the nest is probably old and inactive.
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This beauty is a potter wasp...she's been "shopping" and will bring that caterpillar to her nest. It's pretty amazing to see. (My apologies since I do not remember where I found this picture. As soon as I find the file I will repost, giving credit as due.)
More amazing than the tiny pot on the leave was watching another mud dauber wasp create this nest...
Vocabulary
Mud Dauber - any of several wasps of the family Sphecidae that build a nest of mud cells and provision it with spiders or insects ( dictionary.com )
daub - to cover or smear with a sticky material (thefreedictionary.com/dauber )
Resources
This link is a part of the Texas A & M University site. The site is a wonderful resource for anything to do with insects. While the focus is on Texas, most of the creatures can be found in Massachusetts, too.
A very good, though more professionally oriented, resource.
This is a YouTube video of a mud dauber making a nest. Simply amazing
http://en.wikipedia.org/wiki/Potter_wasp
This is a great entry that provides accurate information and clear photos of wasps and nests.


