On Aug 21, 2006, Magpye from NW Qtr, AR (Zone 6a) wrote:
Stinging rose caterpillars, also known as the rose slug caterpillars, are the bizarre larvae of handsome green and pale brown moths. Mature caterpillars are less than an inch long, and the caterpillars are known to feed on foliage of rose, dogwood, apple, cherry, bayberry, hickory, maple, poplar, and oak. They are said to be aposematically colored.
The black-tipped spines on the elongate body wall projections have poison glands at their bases. Venom enters the skin of humans or animals when the caterpillars are touched and the tips of the spines break off. The caterpillars are said to be capable of producing skin irritation similar to that produced by saddleback caterpillar, which is considered among the most severe urticating caterpillars in North America. Specialized irritating spines, called caltrop spines, are present on the lateral horns of several segments.
In some areas, such as New York State, it is considered a species of conservation concern.