Saddleback caterpillars feed on the leaves of basswood, chestnut, cherry, plum, oak, and other trees and shrubs. The saddleback caterpillar is a general feeder and is generally found on shade trees and ornamental shrubs in late summer.
Adults tend to take flight in mid-summer.
The poisonous hairs or spins are hollow and connected to underlying poison glands. Contact with them causes a burning sensation and inflammation that can be as painful as a bee sting. The irritation can last for a day or two and may be accompanied by nausea during the first few hours. Usually the site of contact reddens and swells much like a bee sting. An ice pack will help reduce swelling, and creams and lotions containing steroids will lessen the discomfort and promote healing.