We’ve been watching these polka dot wasp moth caterpillars (Syntomeida epilais Walker) on my oleander plants. The young caterpillars eat the underside of leaves, but avoid eating anything from the veins of the leaves. As they grow, they become tolerant of the poison in the white sap of the oleander plant, which allows the more mature and larger caterpillars to eat the entire leaf. This is an advantage for the caterpillars since birds avoid eating them due to the oleander chemicals in the caterpillars.
The caterpillars are often found clustered together on the leaves. If there are large numbers of them, they can eat all the leaves on the plant in a few days. The information on the University of Florida IFAS link below recommends that one of the most effective means of control is to cut the branches with the clusters of caterpillars, place the branches in a plastic bag, and freeze them. Although the caterpillars are poisonous to birds, humans are not harmed if you touch them. However, avoid touching the white sap from the oleander plant or wash your hands thoroughly after contact with the sap.
Mature caterpillars tend to search for sheltered locations high off the ground. Their bright orange color makes them easy to spot as they climb up the walls of the house. Right now, there are clusters of them under the eves and in the door frame where each has spun its wispy chrysalis structure.
Although the polka dot wasp moth flies during the daytime and not at night as most moths do, they mate and lay their eggs in the pre-dawn hours.
” In this species, female moths perch on oleander foliage and emit an ultrasonic acoustic signal which, although inaudible to us, attracts male moths from great distances. When male and female moths are within a few meters of each other, they begin a courtship duet of acoustic calls which continues until mating occurs two or three hours before dawn.”
We love the polka dots, the iridescent blue of the wings, the bright red abdomen, and the white tips on the antennae. The first time we saw one was on the 4th of July. It looked like it was celebrating with its patriotic red, white and blue colors. We affectionately call these moths the “blue dudes”. I received a photo today from my daughter-in-law of another one that she had spotted and my granddaughter told me, “The blue dude was sitting on the ground.”