Saddleback Caterpillar

I found this critter crawing around a building here in Oak Ridge. It turns out to be a saddleback caterpillar, which can leave a nasty sting. From the USGS site:

Another unique slug caterpillar. Charcoal black or brown, with unmistakable lime green abdominal saddle. Saddle with central brown patch ringed with white. Dorsum of first and eighth abdominal segments with fingerlike lobes bearing numerous stinging spines. Sting intense and of considerable duration. Food: broadly polyphagous on trees, shrubs, grasses such as corn, and other garden plants.