South Carolina is home to some 165 species of butterflies, including the Red-spotted Purple (Limenitis arthemis astyanax) — arguably among the most beautiful of them all.
It’s a medium-sized butterfly with lush, velvety, bluish black wings. The wing borders are lined with small whitish spots, and there’s a scattering of orange spots at the tips of both forewings. But it’s the shimmering iridescence of its wings that makes this butterfly so striking.
Red-spotted Purples occur throughout most of the eastern half of the United States. A close relative, the White Admiral, or Banded Purple (Limenitis arthemis arthemis), has broad white stripes on its wings. This subspecies is found mostly in the Northeast and in Canada, so we won’t see it down here in the Lowcountry.
But further north, in a narrow zone of overlap, the two variants may interbreed. This hybridization has prompted much research on the evolution, genetics, and ecology of these two beautiful butterflies.
In the Lowcountry, look for Red-spotted Purples in open woods, forest edges, and wooded residential areas. Males spend their afternoons searching for females, adopting look-out perches on sunlit branches and chasing away other males.
Females lay eggs on the leaves of various shade trees, such as cherries and willows. The brown and white caterpillars look remarkably like bird droppings — presumably an adaptation that protects them against predation. This protective resemblance also applies to the chrysalis, or pupal case, within which the larva gradually morphs into a butterfly.
Adult Red-spotted Purples use a different tactic to avoid predation – they mimic the appearance of toxic Pipevine Swallowtails (Battus philenor), which have somewhat similar iridescent bluish-black wings, plus a “tail” on each hindwing. Pipevine caterpillars sequester toxins from Dutchman’s Pipe and related food plants, thus rendering themselves distasteful to predators.
Red-spotted Purples sometimes visit flowers to drink nectar, but they prefer other food sources — fermented fruit, tree sap, even dung and carrion.
As butterflies go, they’re strong fliers and are often wary of humans. But sometimes males can be approached more closely when they’re busy sipping liquids from muddy ground or other wet places.
This “mud-puddling” behavior — also seen in a variety of other butterflies — provides them with salts and amino acids needed to make the sperm packets transferred to females during mating.
In South Carolina, Red-Spotted Purples are found throughout the state, from spring into early fall.