Many stinging caterpillars are mistaken for worms. Some are quite colorful with sparse spikes while others are woolly and tempting to touch. Stinging caterpillars, with their worm-like movements can cause varying levels of pain, from mild to severe.

Thousands of caterpillars and worms exist that employ various means of self-defense. Some feature large eyespots in a pretense of appearing bigger. Others are patterned for camouflage to remain undetectable. Stinging caterpillars, however, often use a blend of coloration and woolly hairs or spikes that serve as a warning to “back off.” While these “worms” eventually turn into interesting moths and beautiful butterflies, in the caterpillar stage they can be downright irritating and sometimes quite painful.

As caterpillars go through several larval stages, they’re referred to as “instars.” Younger instars are sometimes darker in color, including woolly blacks and browns. As they become larger, their ability to cause greater discomfort also increases.

In the case of woolly caterpillars, the “urticating” hairs – and not actual stingers – do the damage. They’re hollow and can transmit venom from poison glands located on the caterpillar’s body. Once the fragile tube breaks or becomes embedded, it releases the toxins.

Some of the more familiar species include:
-Arctiidae: includes hairy and spiny caterpillars in the Tiger moth family.
-Lymantriidae: includes caterpillars of Tussock moths.
-Megalopygidae: caterpillars in the Flannel moth family. The Puss caterpillar in this family is well known for its intensely painful stinging ability.
-Nymphalidae: including caterpillars of Mourning Cloak butterflies.
-Saturniidae: spiny caterpillars in the Silk moth family. Also, Mesquite buck moth caterpillar.

The Io moth caterpillar and the saddleback caterpillar are not as potentially harmful as the Puss caterpillar but are also common. They feed on lower-hanging bushes as well as trees, which makes them a frequent problem in gardens and wooded areas. Indeed, the majority of stinging caterpillars are moth species with far fewer that belong to the butterfly groups.

You can treat the wounded area in several ways. In some cases, the stingers will be embedded in the skin or in clothing. Use strong sticky tape to pull them away. Also, cleansing with soap and water, then applying a disinfecting agent may help dissolve some of the venom. Ice packs followed by a poultice of baking soda may also help reduce pain and inflammation.

Professional medical attention may be required in some cases. The stung area can become infected easily from the urge to scratch at the inflammation. In rare instances, this can lead to a potentially life-threatening condition known as cellulitis. Symptoms include fever, chills, and red streaks spreading outward from the wounded area. Other symptoms may result from an adverse reaction to the toxins. Those that warrant immediate medical attention include swollen lymph nodes, especially near the site or in the groin area. Any indication that the pain or redness is increasing should be attended to immediately.

Most experts agree that prevention is the best solution. Adults should warn children to avoid picking up fuzzy “worms.” While plenty of these interesting creatures are harmless, it is very difficult to know the difference, unless you’re an expert. Sometimes a stinging attack cannot be avoided, however. These caterpillars can drop onto individuals from higher feeding spots and do their damage. Even after the outer skin has shed, or a caterpillar has died, the hairs and spikes can do just as much damage.

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