This time of year is when Processionary Caterpillars come out and make an appearance. These are not creatures you want to tangle with or let your pets near.
What Are Processionary Caterpillars?
Processionary caterpillars, specifically the pine processionary caterpillar (Thaumetopoea pityocampa), are a common sight in many parts of Spain, especially in or near pine forests. These caterpillars are named for their distinctive behavior of moving in long, nose-to-tail processions on the ground. While they are a natural part of the ecosystem, processionary caterpillars pose significant risks to both humans and animals, particularly dogs, due to their urticating hairs.
Life Cycle
- Egg Stage: The life cycle of the pine processionary caterpillar begins in summer when female moths lay eggs in rows on the needles of pine trees. These eggs hatch in late summer or early autumn.
- Larval Stage (Caterpillar): After hatching, the caterpillars feed on pine needles, which can result in significant defoliation of the trees. They undergo several developmental stages (instars), becoming more visible and larger with each stage. During the day, they reside in silk nests they construct on the branches of pine trees, emerging at night to feed in a communal manner to minimize heat loss and predation risks.
- Procession Behavior: In late winter or early spring, the caterpillars leave their nests and descend the tree in long, head-to-tail processions to find a suitable place in the soil to pupate. This behavior is what gives them their name and is a remarkable sight, albeit a potentially dangerous one due to the caterpillars’ urticating hairs.
- Pupal Stage: Once they have buried themselves in the soil, they enter the pupal stage, from which moths will emerge in the summer, completing the cycle.
Dangers to Dogs
Dogs are especially at risk of coming into contact with processionary caterpillars because of their curiosity and the manner in which they explore their environment, often using their noses. The caterpillars have tiny barbed hairs that can become airborne or remain on the ground and vegetation. When a dog sniffs or licks a caterpillar or its trails, these hairs can embed in the mucous membranes of the mouth, tongue, or throat, leading to severe reactions including:
- Intense Pain and Swelling: The immediate effect of contact with the caterpillar hairs is intense pain and swelling. This can cause the dog to paw at its face, drool excessively, or exhibit signs of distress.
- Tissue Necrosis: In severe cases, the embedded hairs can cause tissue necrosis, leading to parts of the tongue or throat tissue dying, which might require surgical removal.
- Difficulty Breathing: Swelling in the throat can obstruct the airway, making it difficult for the dog to breathe.
- Allergic Reactions: Some dogs may have allergic reactions, further complicating their condition.
Dangers to Humans
Humans are also at risk, though typically to a lesser extent because we are less likely to directly touch or disturb these caterpillars. However, contact with the hairs can occur through the air or by touching objects that have come into contact with the caterpillars. The risks include:
- Skin Rashes: Contact with the hairs can cause skin rashes, itching, and irritation.
- Eye Irritations: If the hairs get into the eyes, they can cause redness, swelling, and itching. In severe cases, it can lead to more serious eye injuries.
- Respiratory Issues: Inhaling the hairs can cause respiratory problems, such as coughing, difficulty breathing, or an allergic reaction, particularly in individuals with pre-existing respiratory conditions like asthma.
Management and Prevention
In areas where processionary caterpillars are common, local authorities often take measures to control their population and reduce risks, such as applying biological control agents or physically removing nests from trees during the winter before the caterpillars descend. For individuals, precautionary measures include:
- Avoid contact with the caterpillars and their nests.
- Keeping pets on a leash and away from known infested areas during the caterpillar season, which typically peaks in late winter and spring as the caterpillars descend from the trees to burrow into the ground.
- Seeking immediate veterinary care for pets that have come into contact with these caterpillars.
- Consult a doctor if you or someone you know has a severe reaction after potential contact with processionary caterpillars.
Awareness of the risks associated with processionary caterpillars and taking appropriate precautions can help protect both humans and pets from their harmful effects. Avoid the temptation to stamp on these creatures as the risk far outweighs the rewards.
Contact your local Ayuntamiento and let the town hall sort out these nests.
