I saw these house-building caterpillars last week outside of my office at SERC in Edgewater, MD. Anyone know the species? I will rear a few out to adults to figure it out. I'll post here if I can figure it out. Please let me know or post a comment if you recognize it!
UPDATE July 7, 2010: Dean Janiak helped me find it on bugguide.net - It's a bagworm moth, genus Thyridopteryx!