Caterpillars of this species grow to 3 inches long, are black with red bands between the body segments and clusters of short stiff spines. Host plants include weeds and some landscape plants. Overwinters as a larva. Caterpillars of the woolybear caterpillars in the fall are thought to indicate the severity of the oncoming winter by the proportion of red-brown to black on the body, although this is good folk lore, there is apparently no scientific evidence supporting this idea. Adults occur in the spring.
Caterpillars have chewing mouthparts.
Adults have siphoning mouths. Saltmarsh caterpillars are general feeders, eating leaves of weeds and grasses. Partially-grown caterpillars often migrate into row crops such as soybean fields, gardens and landscapes. Woolybear caterpillars feed on leaves of weeds and grasses. Caterpillars feed on leaves and may cause a problem when occurring in high numbers on landscape plants or crops.