Question
I was clearing an overgrown area in my yard (in Southern Illinois) this weekend and came across some very long vines with an unexpected bite.  The vines were bright green and seemed to grow primarily along the top of the surrounding overgrowth.  The vines were mostly bare with occasional, small bunches of oblong leaves (maybe saw-edged leaves, I don't clearly remember).  The vines were covered all over with tiny, almost hair-like, teeth that grabbed onto my arms like Velcro tape.  The scratches they left were only surface, but within seconds they stung almost like a mild bee sting.  The sting left after washing with soapy water, but I can still see the scratches today.  Obviously, it's just a nuisance, but I would like to know what we're dealing with.  Thanks for any help you can offer!

Answer
Okay, I've asked around here in my area (mid-Atlantic) and I think that perhaps what you have is not a true "vine" but a perennial that spreads via stolons/runners, called Stinging Nettle.  The leaves are bright green, serrated, and the plant is pretty much covered with scratchy, stinging little "hairs," right?  I went to a couple of books and found some good photos of Stinging Nettle, and this plant seems to fit your description.  What do you think - a possibility?