Thank you for your question. This is a female Yellow Garden Spider, also called the Writing Spider. The scientific name for this species is Argiope aurantia. It is in the orbweaver family Araneidae. It is a common species from Canada to Costa Rica.
The female spins a large web, up to 0.75 meters in width, usually in open areas of vegetation, like gardens. We usually have at least one in our iris beds each year. They get the name writing spider from the bold zig-zag portion in the center of their web. These are called stabilimenta and help stabilize the central portion of the web. They are also thought to prevent large insects from tearing up the web when they fly into the center. Some recent studies suggest that the stabilimenta may absorb ultraviolet rays in a way that actually attracts insects.
Males are much smaller than the females and darker in color.
The female constructs a large sphere-shaped egg sac with an urn-shaped opening and attaches it to woody vegetation. Females in our iris beds have attached their egg sacs to our garage wall. Spiderlings hatch in late fall or spring, and mature into adults by mid- to late summer.
Almost all spiders, including this species, are venomous, but this species, unlike the black widow, for example, is not considered to pose a threat to humans.
An excellent guide to spiders in your area is Spiders Of The Eastern United States - A Photographic Guide, by W. Mike Howell and Ronald L. Jenkins.
Hope this answers your question, and thanks for using Ask an Expert.