As common as these spiders are in the books I read, this was the first time I'd seen one in my yard. (A while back I saw a much larger, related species in Roxborough State Park. That one was probably four times the size of this quarter inch one.) This gal was easier photographed from the ventral view because that pretty mottled green background is made of my very prickly blackberry vines. I got a couple dorsal shots, but shed a little blood to do so.
The round nodule on the posterior consist of spinnerettes, anus and anal papilla (according to http://webs.lander.edu/rsfox/invertebrates/argiope.html) . I am a somewhat sheltered girl (I will ignore the snickers I hear from certain readers), so I had to look up the word papilla. Weird.
There's some of the web decoration that Argiope is known for. I hadn't realized that there was so much discussion on the matter of purpose in decorating the web.