The Viceroy’s wings feature an orange and black pattern, and over most of its range the Viceroy mimics the Monarch Butterfly. This mimic behavior has a name: Müllerian mimicry. It is a natural phenomenon in which two or more distasteful species, that may or may not be closely related and share one or more common predators, have come to mimic each other’s warning signals. 
The Monarch is loaded with toxic substances known as cardiac glycosides, which it acquires as a result of feasting on milkweed plants as a caterpillar. These substances render it unpalatable to many of its predators, and its brightly colored wings serve as a warning sign of its toxicity. 
Take a look at the side-by side comparison of the Monarch and Viceroy below:
The caterpillar feeds on trees in the willow family including willows, poplars and cottonwoods. 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. Adult viceroys nectar on milkweeds, thistles and other common flowers.