Les Harrison is the UF/IFAS Wakulla County Extension Director
“Beauty is in the eye of the beholder” is a well-known phrase, commonly associated with physical attractiveness. In the case of Io moths, beauty is in the beholder of the eyes. Whether one sees the insect as “attractive” or not, depends on whether one chooses to view Io caterpillars and moths as pests.
The painful sting inflicted by the barbs located on the caterpillars back is reason enough to doubt the value of this creature, but these features are not redeemed by the usefulness of the moth–Io moths have no mouth-parts; therefore, they are not active pollinators!
Io moth caterpillars are one species in this group of stinging insects. They are not especially finicky in their diet selections, so they may be encountered on a variety of plants and trees.
Their mostly green, tubular bodies are easily hidden among the oaks, dogwoods, redbuds and other leafy plants and trees which flourish in Wakulla County. Regrettably, they quickly make their presence known if blundered into when enjoying the outdoors.
The tiny, needle-sharp spines, which cover their body, are an excellent deterrent to any bird or animal which considers this caterpillar as a snack option. Each spine is a hollow tube, filled with a toxin and topped with a sharp point.
A chance encounter resulting in physical contact will rupture the tube and deliver the toxin beneath the surface of the skin. An almost instantaneous burning sensation occurs, followed by pain, swelling and reddening of the affected area.
Early stage caterpillars are quite active and are seen in groups, sometimes moving in single file over a host plant. As they grow, they change from orange to bright green and grow the defensive spines.
When mature, the caterpillars spin delicate cocoons of brown silk. With an irregular and rough appearance, some will be located on leaves of lower branches, while others will populate the base of host plants.
The Io moth usually emerges from the cocoon in the hours near noon. The entire exit is quick, taking less than 10 minutes.
These moths fly only after dark, usually during the few hours past sunset. Their only defense as adults are two large eyespots on their wings, which, when the moths are stationary, appear to be a large, partially hidden, predatory creature.
The onset of reproductive activities occurs quickly, with the use of pheromones to attract a mate. Once the female lays her eggs, she rests for the remainder of her life.
While there are many moths in North Florida which aid with plant pollination, the Io moth is not capable. They have non-functioning mouth-parts and never eat during adulthood.
As quickly as the tiny, white eggs hatch, the life cycle resumes, along with the threat of an accidental encounter.
To learn more about stinging caterpillars in Wakulla County, contact your UF/IFAS Wakulla Extension Office at (850) 926-3931 or https://blogs.ifas.ufl.edu/wakullaco/
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