Source: Public Health Image Library (PHIL). Richard F. Darsie Jr., PhD. Available online: http://phil.cdc.gov

The puss caterpillar, or woolly slug, is the most poisonous caterpillar in the United States. Its poison is hidden in hollow spines among its hairs. This hairy caterpillar is found in the southern states, ranging west through most of Texas and north to Maryland and Missouri. It feeds on shade trees such as elm, oak, and sycamore. Puss caterpillars vary in size from 1.2 in. (32 mm) to 1.4 in. (36 mm).