The Large Yellow Underwing caterpillar, Noctua pronuba, is a common sight in gardens and fields across North America and Eurasia. Many people wonder about the safety of this relatively large larva, particularly when children or pets are present. This article aims to provide clear, science-backed information regarding the toxicity of this specific caterpillar species and explains what to do if you come into contact with one.
Is the Large Yellow Underwing Caterpillar Toxic?
The Large Yellow Underwing caterpillar, often referred to as a “winter cutworm,” is generally not considered toxic or venomous to humans or domestic animals. Unlike some caterpillar species that possess specialized stinging hairs connected to venom glands, this species lacks such a defense mechanism. This means that physical contact or even accidental ingestion is not expected to result in a systemic poisoning reaction.
While there are rare reports of illness in domestic animals after consuming a large quantity of these caterpillars, the cause is not definitively linked to a specific toxin. For the average person, the caterpillar is harmless beyond its status as an agricultural pest.
Key Characteristics for Identification
Accurate identification is important to ensure that you are, in fact, dealing with the Large Yellow Underwing caterpillar and not a different, potentially irritating species. This larva can grow quite large, reaching up to 2 inches (50 mm) in length when fully mature. Its coloring is highly variable, ranging from pale green when newly hatched to shades of dull brown, gray, or reddish-brown in later stages.
A distinguishing feature is the pattern of dark markings along the body. Look for two rows of black dashes that run along the sides of the caterpillar’s back, with these marks often becoming more prominent toward the rear end. The caterpillar is a “cutworm,” meaning it hides just under the soil, beneath debris, or low down on plants during the day. It is primarily a nocturnal feeder, emerging at night to chew through plant stems at the base.
Potential Contact Reactions and First Aid
While the Large Yellow Underwing caterpillar is not poisonous, contact with any hairy caterpillar can sometimes result in mild skin irritation. Although this species does not have venomous spines, the fine hairs on its body may cause a localized reaction, known as dermatitis, in some individuals. This is more likely to occur in people with highly sensitive skin or those with pre-existing allergies.
If skin contact occurs, the reaction is usually limited to symptoms like redness, mild itching, or the formation of small welts. These symptoms are generally localized to the area of contact and typically resolve quickly. The first step in treating this minor irritation is to remove any residual hairs that may have broken off on the skin.
A simple and effective method for hair removal involves gently pressing adhesive tape, such as duct tape, onto the affected area and pulling it off to lift the hairs. Following this, the area should be washed thoroughly with soap and cool water. Applying a cold compress can help reduce any swelling, and an over-the-counter hydrocortisone cream or oral antihistamine can alleviate persistent itching.
Seek medical attention if symptoms worsen, if you experience widespread swelling, or if any respiratory distress occurs, as rare allergic reactions can affect the airways.