Common Wood Nymph butterflies are also known as: Large Wood-nymph, Grayling, or Blue-eyed Grayling. Wood Nymphs are Sartyrs, which are a subfamily of brushfoot butterflies. Common Wood-nymphs are found in woodlands, meadows, and slow water courses throughout much of North America. Their eggs are ribbed and yellow. Caterpillars are grass green with yellow lines. Their host plants are grasses. Here is one I saw while in northern Minnesota.