An Exception to the Rules

The exceptional and beautiful polka-dotted wasp moth (Syntomeida epilais) breaks a number of Mother Nature’s rules:

Palkadotted wasp moth  (Syntomeida epilais) 

on Spanish needles (Bidens alba).

#1. Adult moths fly at night. Fortunately for photographers, this beautiful moth flies in the daylight hours.

#2. Adult moths have pale or pastel colorations. With their iridescent gunmetal blue coloring punctuated by white dots and a bright red tip on their abdomens, these insects mimic wasps and display the warning coloration that tells birds that they are dangerous. As larvae (caterpillars) they consume poisonous foliage, so this is not an entirely false warning.


#3. Moths and butterflies emit pheromones (attracting scents) to attract mates. The female polka-dot wasp moth emits ultra sonic sounds to attract a mate, not the scented pheromones like most other moths and butterflies. When the male comes within a few feet he'll start clicking as well. Some researchers have studied this habit in relation to bat populations. The theory is that decreasing bat populations make the sound emissions less dangerous.

#4 Moth larvae will only consume certain species of plants. This is why as wildlife gardeners we plant a wide variety of native plants to serve as larval food sources for butterflies and moths. The polka-dotted wasp moth is native to south Florida and the Caribbean Islands and researchers think that it originally used the devil's potato (Echites umbellatus), a member of the dogbane family (Apocynaceae) as the main host plant for the caterpillar. This family includes an interesting collection of poisonous-sap plants including milkweeds, frangipani, allamanda, deviltree, periwinkle, cape jasmine, and oleander.

The devil’s potato is relatively rare and its range
 is limited to southeast Florida.

Wasp moth on dogfennel flowers (Eupatorium capillifolium)

these interesting moths are quite prolific when given
plenty of larval food.

These days the polka-dotted wasp larvae are sometimes found on other members of the dogbane family such as milkweeds, but they mostly they have switched to oleander (Nerium oleander) as their main host plant and have increased their range with the plantings of this Mediterranean shrub. The Spanish brought oleanders to Florida in the 1600s and now, except for California, the polka-dot wasp moth is found wherever there are oleanders in the Americas. A group of these ravenous caterpillars can strip bare an entire shrub in a matter of a day or two. Now the other common name for this insect is the oleander moth and it has become a significant pest in the landscape.

Isn’t Mother Nature fun to study? Here's a case where one of her exceptional creatures has taken advantage of new plants introduced into its environment.

Post by Ginny Stibolt.