As @
thejakemoore mentioned, I've seen the suit, and he is correct for the most part--- the base layer of the chest spider is the same rubberized material as the webs, but it has a very thin appliance on top of that. A second layer that is more reflective than the rest of the suit, but not glossy, it catches more light from more angles as you walk around the suit (not unlike retroreflectors in athletic shoes, though not as extreme). It has a fine granular texture, and is the only part of the costume with this more reflective material.
http://i.imgur.com/SOoPHb9.jpg
http://i.imgur.com/Wc7zSzX.jpg