Dirt Dauber Wasp

"These shiny, black mud daubers are named for the type of nest they build. As with the black and yellow mud dauber, the organ pipe species' female utilizes her mandibles to collect mud and form a nest. The parallel tube structure of this mud dauber's home resembles the cylindrical pipes of an upright organ. Like the other species of mud dauber, the organ pipe wasp employs parasitic habits, paralyzing spiders for later consumption by larvae. The organ pipe and other mud daubers are considered beneficial, as they prey upon poisonous spiders that lurk in and around man-made structures." -Info from Flower Mound Pest Control blog, June 5, 2011

Family Sphecidae http://en.wikipedia.org/wiki/Sphecidae Probably some species in the genus Chalybion http://en.wikipedia.org/wiki/Chalybion