Took a long, hard look to convince ourselves this was a spider and not poop or a gall. Behold the bolas spider, perfumier and ropemaster.

Here's my trace through Levi (2003):

1. Abdomen with humps
2. Abdomen with only one pair of humps
3. Carapace with median tuburcles smaller than horns
4. Carapace sides with few or no tuburcles
5. North America
6. North America
7. [northeastern US; the only other option in range down the other branch is M. cornigera, but the range is more southerly and the tuburcles look more pronounced to me]

Also, I invite you to gaze lovingly upon the adorable figure 153 at http://biodiversitylibrary.org/page/4290852