Nymphidium is a genus in the butterfly family Riodinidae present only in the Neotropical realm. Some Nymphidium are obviously secondarily transformed by mimicry, otherwise the almost exclusive colours are brown and white either of which being now and then preponderant. The wings have a normal shape without indentations, tail appendages, lobing or coiling. The larva is shaped like a woodlouse, hunched, green, sometimes with a yellow lateral streak, the neck organ out of a transverse row of green spikes or bristles. It has a guard of ants. The pupa is green, fastened by a belt-like thread. The butterflies rest on the under surface of leaves and are chased up by beating the bushes, whereupon they fly like Geometridae for some paces, in order to hide themselves again. The swarming-time seems to be dawn, or the early morning, but the author came across them yet in the sunshine of the morning on blossoms. They are easily taken and fly low.