The saddleback caterpillar (Acharia stimulea) is a distinctive insect found across eastern North America. While not poisonous if ingested, it is venomous and can inflict a painful sting upon contact. This caterpillar possesses specialized stinging spines that release an irritating venom, making it a creature to approach with caution. Accidental encounters can occur in gardens and wooded areas, leading to an uncomfortable experience.
Identifying a Saddleback Caterpillar
Recognizing the saddleback caterpillar is key to avoiding its sting. It typically measures around 0.75 to 1 inch in length when mature. Its body is primarily bright green, often described as resembling a saddle blanket, with a prominent oval-shaped, brown or purplish-brown spot in the center of its back, which gives it its common name. This central “saddle” is often bordered by a white ring.
The saddleback caterpillar features four prominent, fleshy knobs or horns, two at the front and two at the rear of its body. These, along with smaller knobs along its sides, are covered in stiff, spiny tubercles that bear stinging hairs. Its vibrant coloration serves as a warning to predators. These caterpillars are often found on the leaves of various trees and shrubs, including oak, cherry, maple, and corn, particularly during late summer and fall. They move in a unique, slug-like manner, as they lack typical prolegs.
How Saddleback Caterpillars Cause Harm
The harm from a saddleback caterpillar comes from its venomous spines, not from ingestion. These caterpillars are equipped with numerous hollow spines, often orange or black, that cover their body, including the prominent knobs. Each spine is connected to a venom gland.
When skin brushes against the caterpillar, these fragile spines easily break off and embed themselves. Upon breaking, the venom is released into the skin, causing an immediate reaction. This defense mechanism means caution is needed, as spines can also detach onto surfaces, requiring caution even without direct contact with the caterpillar itself.
Symptoms and Treatment of a Sting
A saddleback caterpillar sting causes immediate and intense pain, often described as a burning or stinging sensation similar to a bee or wasp sting. The affected area typically develops redness, swelling, itching, and a rash or welts. The pain can sometimes spread to nearby lymph nodes.
In some individuals, systemic reactions can occur, including nausea, headache, and localized muscle cramps. While severe allergic reactions like anaphylactic shock are rare, they are possible. If stung, first remove any visible spines. This can be effectively done by repeatedly applying and pulling off adhesive tape, such as duct tape or scotch tape, over the affected area to extract the embedded hairs.
After spine removal, gently wash the area with soap and water to clean the wound and help remove any remaining venom. Applying an ice pack or cold compress to the site can help reduce pain and swelling. Over-the-counter pain relievers can manage discomfort, and antihistamines or hydrocortisone creams may alleviate itching and inflammation. It is advisable to seek medical attention if symptoms are severe, worsen, or if signs of infection develop, or if you experience symptoms of a severe allergic reaction.
Preventing Encounters
To prevent painful encounters with saddleback caterpillars, exercise caution, especially when working in gardens or wooded areas. Wearing protective clothing, such as long-sleeved shirts and gloves, when handling plants, garden debris, or pruning during late summer and fall can reduce the risk of contact.
Visually inspect plants before touching them, as these caterpillars often reside on the underside of leaves or branches. Educating children about the dangers of touching unfamiliar caterpillars is important, as their appearance can be deceptive. While saddleback caterpillars feed on a wide variety of plants, they do not typically cause significant damage to landscapes due to their low numbers, so chemical controls are generally unnecessary.