WILDLIFE OF THE WEEK
Polka-dot Wasp Moth
I’m always delighted to get photo ID requests from readers. It’s delightful way to get to know fellow nature-lovers and always gives me a chance to practice my naturalist skills, especially with folks who live in different locales. Beyond that, I often end up learning new species that I myself have never encountered. This week, I’m excited to share this “What is it??” photo I received from a reader. The beast in question was a strange-looking caterpillar trundling its way across the sidewalk. While I initially suspected it was a type of tussock moth, famous for their funky hair-dos, iNaturalist pegged it as the Polka-dot wasp moth. Yes, that’s its real (common!) name!
A specialty wasp in subtropical areas of North America, this moth’s zany-looking caterpillar didn’t lead me totally astray: they belong to the same family, Erebidae, as the tussock moths I was thinking of. This species’ larvae feed on oleander, a widespread ornamental shrub (super common in Florida so that checks out!) famous for being pretty and highly poisonous. Aside from their wild diet, the species is particularly fascinating as a mimic: as adults, they look very little like a moth, and much more like a bright and colorful wasp.
The moth’s sharp-looking antennae, narrow, shiny wings, pronounced head, long legs, and slender a abdomen all suggest a wasp’s body shape, a great example of Batesian mimickry - when a harmless organism imitates a harmful one so predators leave it alone. The moth’s characteristic polka dots, themselves likely imitating a wasp species found somewhere in its massive global range (the species likely came from the Mediterranean, but the oleander plant has been moved around too much for thousands of years for people to be sure!), are an example of aposematic coloration - warning colors to keep predators away.
Although this wasp-wannabe can’t sting, those spots aren’t entirely a fib: since their larvae eat notoriously huge amounts of oleander as they grow up, these moths may be carrying around a substantial amount of oleander poison. I noticed in a bug guide that I was thumbing through that, while munching, the caterpillars are careful not to bite into the leaf veins of the plant, therefore avoiding the brunt of its poison. If that’s the case, I wonder whether they carry around enough poison to be dangerous, or just a little?
The fact that Polka-dot wasp moths fly unbothered by birds in broad daylight, and not at night like many other moths, is enough clue for me to decide not to find out.
The original photo—a Polka-dot wasp moth larva makes its way determinedly across a sidewalk, bearing a formidable armament of hair-tufts. These are harmless but might make a larger predator think twice, or foil the attacks of a pack of ants.
Oleander (Nerium oleander), the food plant of the polka-dot wasp moth and a common ornamental, especially in the subtropical areas of North America.
RELATED POSTS
This week’s reader question brought to mind a lot of useful posts from Gulo in Nature - check out some helpful supporting info here:
LATEST BLOG POST
My latest post comes directly from conversations with curious readers and nature walk companions. “Why do animals have tails?” is one of my favorite kinds of nature questions: it sounds a little silly, even childish at first, but answering it leads you through a lot of topics on biology and natural history. As such, it’s a fun lead into a romp through our natural world. I tackled this deceptively complex question with a full scientific breakdown—from what tails actually are (anatomically and phylogenetically speaking) to 11 fascinating reasons animals have them. Check it out to find out the deep history of tails, their many uses, and how they showed up on the scene. As always, please share with friends and fellow nature-lovers!
NATURALIST WORD OF THE WEEK
Crepuscular (adj.) - most active both at dawn and dusk. Many mammals are crepuscular, and dawn and dusk are some of the best times for spotting larger wildlife.
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