Vivid orange and black warning coloration and resemblance to a wasp may help the beautiful spotted oleander caterpillar moth escape hungry predators.
When colonists brought oleander to the New World, this plant of Mediterranean origin was readily fed upon by the spotted oleander caterpillar, a native of the Caribbean region.
As winter tightens its grip in the United States, Bug of the Week continues its adventures in tropical places with a quick stop in the Antilles to catch up with another member of the tiger moth clan, the spotted oleander caterpillar moth, a relative of the last week’s featured guest, the polka-dot wasp moth.
When European colonists arrived on islands such as Cuba and Guadeloupe, they brought along the beautiful but deadly woody shrub, oleander. Leaves, flowers, and fruit of oleander are laced with heart - stopping poisons known as cardiac glycosides. We met oleander and learned of its poisonous qualities in last week’s episode of Bug of the Week. Apparently, oleander was suitable tucker for the island native, Empyreuma affinis, a.k.a spotted oleander caterpillars, and the brightly colored day-flying adult moths soon added this Mediterranean plant to the list of suitable places to deposit eggs.
The spotted oleander caterpillar dines with great gusto on non-native oleanders, like its cousin the oleander caterpillar.
Most moths seek nectar and deposit eggs at night cloaked by darkness from the searching eyes of hungry predators. However, like the polka-dot wasp moth we visited last week, the gaudy spotted oleander caterpillar moth is believed to gain protection from visually hunting predators by resembling a stinging wasp. In addition to resembling a nasty stinging insect, the moth’s vivid coloration warns predators experienced with brightly colored noxious prey to bugger- off and find a more delectable meal elsewhere. It has been suggested that spotted oleander caterpillars obtain noxious heart-poisons from the oleander plants on which they feed and pass them along to the adult moths. By taking a taste of these flashy toxin-laced insects, birds experience their noxious emetic properties and soon learn to avoid making a meal of brightly colored moths and caterpillars.
In last week’s episode we also learned of the interesting courtship behavior of the polka-dot wasp moth. The polka-dot wasp moth relies on ultrasonic communication including reciprocal duets to complete the mating ritual. However, females of the spotted oleander caterpillar moth rely on chemical communication in the form of pheromones to attract their mates. Like a mixed media combination of a rock concert and perfumery, acoustic communication and mating of the polka-dot wasp moth occurs in the waning hours of night between 2:30 and 4:30AM, and the pheromone-driven wooing of the spotted oleander caterpillar moth takes place in the wee hours of the morning just before and during dawn. Romantic creatures are these tiger moths.
Feathery antennae enable the male spotted oleander caterpillar moth to detect sex pheromones released by the female onto the morning breeze.
If a trip to the Antilles is a little beyond your travel budget, but you yearn to witness the spotted oleander caterpillar moth and its larvae, no worries. Our global economy has shrunk the world and global trade and transit have brought this fascinating insect to Florida, where it was first discovered in Boca Raton in 1978. During your quest to see the native polka-dot wasp moth in Florida, don’t be surprised to encounter its immigrant spotted cousin also dining on oleander.
Spotted oleander caterpillars are easily distinguished from oleander caterpillars by the spots and hair tufts lining their bodies.
Spotted oleander caterpillars have light colored spots and reddish-brown hair tufts.
Their cousins oleander caterpillars have dark spots and black hair tufts.
References
The fascinating book “Tiger Moths and Woolly Bears”, by William Conner, and the wonderful Featured Creature article by Heather McAuslane, “Spotted Oleander Caterpillar, Empyreuma affinis Rothschild…” were consulted for this episode. To learn more about the spotted oleander caterpillar moth, please visit the University of Florida Featured Creature web page at the website below:
http://entnemdept.ufl.edu/creatures/orn/spotted_oleander_caterpillar.htm