Life Cycle

• Oleander caterpillars are the larvae of the polka-dot wasp moth. Not remotely resembling a butterfly or moth, it looks like a large wasp with white polka-dotted black wings and a cobalt blue body. The wings are narrow and angled backwards. White eggs, about 1/30 inch in diameter, are laid on oleander leaf undersides. They hatch into small orange caterpillars that consume leaves for up to 19 days, molting up to six times and enlarging to about 1 to 1 1/2 inches in length. The caterpillars then pupate in silky cocoon clusters and hatch out as winged adults.
  
  

Leaf Damage

• The first signs of oleander caterpillars manifest on healthy leaves. The chewing mouthparts create a skeletonization -- creating holes in leaf blades in between veins. The chewed leaf parts turn light beige while the remainder of the leaf stays healthy green. Tiny, younger caterpillars often hide on leaf undersides, but the plumper, hungrier caterpillars crawl everywhere for a meal. Extreme infestations by large caterpillars can defoliate an oleander shrub.
  
  

Affected Plants

• If oleander shrubs do not exist in the landscape, or all extant shrubs already have be defoliated, other plants can serve as food sources. According to the University of Florida, oleander caterpillars do not exist in the American Southwest and California, but do in Florida and along the Gulf Coast. Any other member of the dogbane plant family, Apocynaceae, can become their food. Desert-rose (Adenium obesum) and wild allamanda (Urechites lutea), for example, are attacked by oleander caterpillars in South Florida.
  
  

Control

• Birds do not eat oleander caterpillars because they are full of toxins from oleander plants. Stink bugs, parasitic tachinid flies and wasps, red fire ants and spined soldier bugs all eat oleander caterpillars. These beneficial insects often do not exist in large enough numbers to prevent damage to oleander shrubs in summer. Caterpillars may be picked off and destroyed or drowned in soapy water. The hairs on the oleander caterpillar do not sting. Gardeners can spray plants with the microbial bacterium Bacillus thuringiensis, known as Bt, which is ingested by the caterpillars as they eat leaves. Repeated applications are needed after heavy rains.