Gypsy moths (Lymantria dispar) are an invasive species in North America, known for their caterpillar stage that can cause considerable defoliation of trees. As these insects are often present in residential and recreational areas, concerns arise about their interaction with humans, specifically whether they bite or pose other direct health risks. This article clarifies how gypsy moths and their caterpillars interact with people.
Gypsy Moths and Human Contact
Neither adult gypsy moths nor their caterpillars bite humans in the traditional sense. These insects possess mouthparts designed for chewing and consuming plant material. The primary human interaction comes from the larval or caterpillar stage, which is most active from April through July.
These caterpillars are covered in small, bristly hairs, known as setae, which are the actual cause of human reactions, not bites. These tiny hairs can detach from the caterpillar’s body and become airborne, or transfer through direct contact with clothing or outdoor surfaces. While they are known for defoliating vast areas of forests, their impact on humans is through these physical irritants rather than direct biting.
Skin Irritation from Gypsy Moth Hairs
While gypsy moth caterpillars do not bite, contact with their microscopic hairs can cause an irritant reaction known as gypsy moth dermatitis or rash. This reaction is often characterized by itchy, red bumps, welts, or hives on the skin, sometimes resembling poison ivy. Symptoms can appear within minutes or hours after exposure and typically last from one to several days, though some reactions may persist for up to two weeks. The severity of the rash varies among individuals, depending on their sensitivity and the extent of exposure.
The skin irritation is a result of either physical irritation from the barbed setae or an allergic reaction to substances, including histamine, found within these hairs. These hairs can break off and embed in the skin, releasing irritating compounds that trigger the body’s response. In addition to skin reactions, some individuals may experience hay fever-like symptoms, such as a runny nose, watery eyes, or sneezing, if the airborne hairs are inhaled. More serious reactions, including shortness of breath or difficulty swallowing, can occur if mucous membranes are affected, especially in sensitive individuals or young children.
Protecting Yourself from Gypsy Moths
To minimize the risk of skin irritation from gypsy moth caterpillars, avoiding direct contact is a primary protective measure. Do not handle the caterpillars directly, even if they appear harmless. When spending time in areas known to have gypsy moth populations, especially during the caterpillar season from April through July, wearing protective clothing can help. Long-sleeved shirts, long pants, and gloves can create a physical barrier against the irritating hairs.
After potential exposure, it is important to wash any exposed skin thoroughly with soap and water to remove any lingering hairs. Clothing worn in infested areas should also be washed promptly to prevent further irritation or spread of the hairs, as setae can travel through fabric.
Be mindful of outdoor furniture, play equipment, or other surfaces where caterpillars or their detached hairs might accumulate, and clean them regularly. Inspecting and cleaning these items before use can prevent unexpected contact. Removing debris like old wood piles or leaf litter from your yard can also reduce potential hiding spots for egg masses and caterpillars.