Female humpbacked orbweaver (Eustala anastera)
Humpbacked orbweaver spiders (Eustala anastera) are identified primarily by the little bump on the end of their abdomen (sort of visible in this photo) and by lichen-green coloration (although they also come in orange and rusty brown colors). They are pretty variable, pattern-wise; you can see some of the color variation here.
This one has caught something and is hanging upside down on a single thread line, eating it.
Female humpbacked orbweaver (Eustala anastera)
Humpbacked orbweavers can be found throughout the eastern United States and into Canada, in a wide variety of habitats.
Believe it or not, the photo below is of a completely different spider, completely different location, completely different day. If you look closely at her pattern, especially at the cranial end of her abdomen (where the “neck” of her “violin” might be) you can see some differences between her and the previous spider.
Female humpbacked orbweaver (Eustala anastera)
Female humpbacked orbweaver (Eustala anastera)
Female humpbacked orbweaver (Eustala anastera)
Female humpbacked orbweaver (Eustala anastera)