These caterpillars seem to be everywhere at this time of year. While they are not poisonous, they can cause a stinging rash. Best to look, not touch!
“The hairs on the caterpillar are long and bristle-like and spread out in tufts down the sides. Two long, sharp, black pencil-like hairs protrude near the front and rear of the creature, and these hairs are connected to poison glands, which excrete venom on contact.
Contact with the venom does not generally cause too much of a problem. A nettle or poison ivy-type rash often occurs, which can range from mild with slight reddening of the skin, to burning, swelling and pain, none of which should keep you away from your gardening duties for too long. Hypersensitive individuals may, of course, experience more severe symptoms that could include swelling and nausea. Washing the infected area with soap and water, taking antihistamines, or using ammonia, calamine lotion, or an ice pack can help to alleviate most minor symptoms fairly quickly. People who do experience more severe reactions, however, should seek expert medical advice as soon as possible.”