Viceroy (aka Not a Monarch)

Most of the time when you see a slightly large orange butterfly with black "veins" in NJ, you're seeing a Monarch. But not all the time. Every once in a while you could be seeing a Viceroy (this this guy).

While they look quite similar, there is an excellent field mark to tell the difference. There's a dark line that parallels the back wing; see the circled blue in the 2nd picture.

Though both the Viceroy and the Monarch look similar and can be found nectaring on flowers, their lives also have important differences. As you've probably heard by now Monarch caterpillars eat poisonous milkweed plants and become poisonous themselves as a result. Something similar happens with Viceroys, but as caterpillars they eat trees in the willow family, absorb salicylic acid from the trees, and become somewhat poisonous themselves. This is why their relationship with Monarch is now considered to be Mullerian mimicry, where both species benefit from looking like one another.

Their winter strategies are also completely different. Monarchs get through the winter as adults by flying south (ours go to Mexico), and then the adults breed and start moving north in the spring. Viceroys overwinter as caterpillars, reinforcing a leaf's attachment to its tree, then rolling up in its leaf blanket for the winter. When spring arrives, the caterpillars have new, fresh leaves to eat, and their caterpillar development resumes.

Despite looking like the Monarch, the Viceroy is much more closely related to the Red-spotted Admiral (picture here).

July 17, 2022 at Duke Farms
Photo 222063054, (c) jpviolette, some rights reserved (CC BY-NC)

The extra black line, never seen on the Monarch and always present on the Vicerory, is circled below.