Mike is a girl. I'm still going to call her Mike. We don't need no stinking gender restricting stereotypes around here.
My favorite nerds at www.bugguide.net identified Mike in record time. She is a type of Orb Weaver. And we know that she is a she because she was sitting up high in a web that she built. The males of the species do not build webs. They spend their lives wandering around looking for chick-spiders to hook up with. After they mate, they die. That must be quite the one-night stand. (I'll bet he doesn't even cuddle when it is over.)
You might be familiar with a very famous Orb Weaver:
