Caterpillars may be light green, yellow, pink tan, or even a reddish-brown. It is wide and flat unlike the more popular tubular body shape. Rows of yellow or orange stinging spines line the caterpillar from head to rear. Pairs at the head and the rear are longer than those running down the center of the body. These spines contain venom meant to deter predators from eating it. When touched by humans, the spines can embed themselves into skin and cause pain, itching, burning, irritation and redness. If stung, one should use fresh pieces of (Scotch) tape to help pull the spines out of the skin right away, then ice the area and cover it with a baking soda paste. Though it is not considered lethal, people allergic to other insect stings may have a reaction that requires medical attention.
Caterpillars have are not host-specific despite their name and feed on thick, old leaves growing on oak, willow, cherry, sycamore, chestnut, redbud and other deciduous trees, so they are ubiquitous in their range. They are not known to feed on a plant enough to cause any real damage to it.