See, I thought it was dew, but upon closer examination it was the spiders' eyes. Dew hadn't formed yet, and the reflection was greenish when the headlamp was in white light mode, and red in red mode. These were the kind of spiders that just crawl around and don't have webs. I always called the bigger ones wolf spiders.
This page talks about it too, although they are in Belize and I was in Virginia.