Nymphalidae is the largest family of butterflies with about 6,000 species distributed throughout most of the world. These are usually medium sized to large butterflies. Most species have a reduced pair of forelegs and many hold their colourful wings flat when resting. They are also called brush-footed butterflies or four-footed butterflies. Many species are brightly colored and include popular species such as the emperors, admirals, tortoiseshells, and fritillaries. However, the underwings are in contrast often dull and in some species look remarkably like dead leaves, or are much paler, producing a cryptic effect that helps the butterfly disappear into its surroundings.
The Viceroy (Limenitis archippus) is a North American butterfly with a range from the Northwest Territories along the eastern edges of the Cascade Range and Sierra Nevada mountains, southwards into central Mexico.
Its wings feature an orange and black pattern, and over most of its range it is a Müllerian mimic with the Monarch butterfly (Danaus plexippus). The viceroy's wingspan is between 53 and 81 mm. It can be distinguished from the Monarch by its smaller size and the postmedian black line that runs across the veins on the hindwing. In Florida, Georgia, and the Southwest, Viceroys share the pattern of the Queen (Danaus gilippus) and in Mexico they share the pattern of the Soldier (Danaus eresimus). In all three areas, the local Danaus population mimic the coloration of the Viceroy species. It was originally believed that the Viceroy was a Batesian mimic of the three other species, and presumed edible or only mildly unpalatable to predators, but this has since proven not to be true.
The caterpillar feeds on trees in the willow family Salicaceae, including willows (Salix), and poplars and cottonwoods (Populus). The caterpillars sequester the salicylic acid in their bodies, which makes them bitter, and upsets predators' stomachs. As further protection, the caterpillars, as well as their chrysalis stage, resemble bird droppings. Adults are strictly diurnal, flying preferentially in the late morning and early afternoon.