I'm very impressed! The Yellow Garden Argiope Argiope aurantia is the largest known web-building spider in Michigan. Yours looks like a female. The males are about a quarter that size. He usually builds his own web in the outlying part of the female's web. These spiders mature in late summer and fall. Look closely for an egg sac to one side of her web or close to her resting position at the center. Each female watches over her eggs as long as she can, but she will die in the first hard frost, if not before.
Because of our cold winter, the eggs of this species hatch in the late summer or autumn, but the hatchling spiders become dormant and do not leave the egg sac until the following spring. Over 1000 spiderlings overwinter inside the cocoon and then hatch all at once in the spring. Tiny and blind at first, they remain near the egg sac for a few days. Soon they molt through more advanced stages until they begin to resemble the adult spider. Unable to feed at first, they subsist on an internal yolk sac.
The web of the yellow garden spider is distinctive: a circular shape up to 2 feet in diameter, with a dense zigzag of silk, known as a stabilimentum, in the center. The purpose of this structure has been a mystery, but recent research has shed some possible light on the subject. These special threads stand out in ultraviolet light possibly attracting insects who can see in UV light. It also may help to disguise the spider who sits right in the middle of the stabilimentum. The entire web is usually eaten and then rebuilt each night, often in the same place.
Source: Spiders of the North Woods by: Larry Weber