Some scenes in nature can feel almost mesmerizing right now. Among them, the long single-file lines of caterpillars marching at the base of pines or oaks. But behind this impressive display lies a real danger. The processionary caterpillars are among the insects most problematic for human and animal health.
Curious children, dogs exploring the ground, or casual walkers may be exposed to their extremely irritating hairs. It’s best to know the risks and the right reflexes to avoid accidents.
Microscopic Hairs, Highly Irritating
Processionary caterpillars are the larvae of a nocturnal moth. In winter they live in silk nests in pine or oak trees. When temperatures rise, typically late winter or early spring, they leave the tree in a procession to the ground where they bury and continue their life cycle.
The issue comes from the thousands of irritating hairs that cover their bodies. These tiny barbs contain a chemical irritant called thaumetopoein. When they feel threatened, the caterpillars release these hairs into the air.
Carried by the wind, they can land on the skin, clothing, hair, or outdoor surfaces like garden furniture. Contact triggers strong inflammatory reactions.
It is also recommended to avoid drying your laundry near infested trees, as the hairs can cling to fabrics and cause irritation when wearing the clothes.
What Symptoms If Contact Occurs?
In humans, exposure to processionary caterpillar hairs can provoke several types of reactions:
- intense itching
- red patches or skin burns
- eye irritation
- cough or breathing discomfort
- sneezing or throat irritation
In more severe cases, especially among people with allergies, swelling or anaphylactic shock can occur. A medical consultation becomes essential.
Dogs and Cats: Frequent Victims
Domestic animals are among the main victims of processionary caterpillars. Dogs in particular are highly exposed, as they explore the ground with their noses and can easily come into contact with the caterpillars or their hairs.
When the animal licks or bites a caterpillar, the irritating hairs provoke a very violent reaction in the mouth.
The most common symptoms are:
- excessive drooling
- swelling of the tongue
- difficulty swallowing
- vomiting
- intense pain
In the most severe cases, the tongue can suffer partial necrosis. Quick veterinary intervention is essential to limit damage.
What To Do If Contact Occurs?
If a person or an animal comes into contact with these caterpillars, it is important to act quickly.
For humans:
- do not rub the affected area
- rinse thoroughly with clean water
- remove exposed clothing
- consult a doctor if there is a significant reaction
For animals, you should see a veterinarian as soon as possible. In the meantime, you can gently rinse the mouth with water to limit the spread of the irritating hairs.
How to Keep Them Out of Your Garden?
Several strategies exist to limit processionary caterpillars around the home.
The eco-traps installed around trunks capture the caterpillars as they descend from the tree to reach the ground.
The pheromone traps catch male moths during the mating period, which reduces egg-laying by females.
Finally, promoting biodiversity can also help. Some bird species, such as chickadees, eat caterpillars and naturally help regulate their population. Installing birdhouses in the garden can therefore be a simple and eco-friendly solution.
A Pest on the Move: Expanding With Climate Change
Formerly limited to the southern regions of Europe, processionary caterpillars are now moving northward. Warmer winters favor their survival and facilitate their geographic expansion.
As a result, many regions that were previously spared must now contend with their presence in parks, gardens, and natural spaces.
In the face of this trend, vigilance remains the best protection. Monitoring trees near your home, avoiding contact with the caterpillars, and raising awareness among children can already significantly reduce risks.
