How to Tell the Difference Between a Monarch & a Viceroy Butterfly

Three butterflies on the stems of a plant bearing dark berries.
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Whether for their delicate beauty or their interesting biology, butterflies are some of the most universally beloved insects on the planet. Chief among these is the classic orange and black monarch butterfly, but another orange and black creature often sneaks into the picture. This is the viceroy butterfly, which looks a lot like the monarch with a few key differences. The average butterfly watcher may wonder how to tell the difference between monarch and viceroy species.

TL;DR (Too Long; Didn't Read)

Monarch and viceroy butterflies look a lot alike and are a good example of mutual mimicry in nature. However, the viceroy butterfly is smaller in size, has a darker orange color and shows a black line that crosses the hindwing. The viceroy also flaps its wings quickly and erratically, unlike its "floating" monarch cousin.

Monarch Butterfly Mimicry

Monarch (Danaus plexippus) and viceroy (Limenitis archippus) butterflies share similar wing shapes and coloration. In fact, it is difficult for the average viewer to distinguish between the two species of butterfly. For a long time, scientists thought the mimicry between the monarch and viceroy butterfly went one way: The viceroy looked like the terrible-tasting monarch to avoid predators. For this reason, people sometimes called the viceroy a “false monarch butterfly.” However, entomologists now believe that the mimicry benefits both species. While monarch caterpillars consume milkweed plants full of cardiac glycosides that render the insect foul-tasting, it turns out viceroy butterflies aren’t very tasty either. Viceroy caterpillars eat willows and poplars that are loaded with bitter salicylic acid. When researchers delved into the idea of mutual mimicry, they found that each species benefits from looking like the other – because they both taste bad.

Monarch vs Viceroy

Of course, human butterfly watchers still want to tell apart the two species of butterfly (without resorting to tasting them). The main differences between the two are size, coloration and flight patterns. The viceroy butterfly is generally smaller than the monarch; the viceroy wingspan is approximately 3 inches while the monarch wingspan is closer to 4 inches. When it comes to coloration, both species are orange and black, but viceroy butterflies have a darker orange color and also show a distinct black line across the hindwing. Perhaps the easiest way to distinguish between the two species from a distance is their flight patterns. Monarch butterflies tend to float and glide in the air while viceroy butterfly wings flap in a faster, more erratic fashion.

While scientists and butterfly enthusiasts alike have always appreciated the similarities between monarch and viceroy butterflies, the idea of mutual mimicry adds another layer of interest to these popular insects. Thanks to some subtle differences in appearance and behavior, distinguishing between the two species is unexpectedly straightforward.