Processionary caterpillars return across France, warn local authorities
Insect has been seen two months earlier than usual in many areas
Mild weather in France means processionary caterpillars are already descending from their treetop nests, which resemble large balls of cotton wool
Joao Serafim/Shutterstock
People in France are being warned to watch out for toxic processionary caterpillars, as mild temperatures encourage their early return.
The caterpillars are a relatively common sight each year in France, however the tiny, irritating hairs covering their bodies can cause irritation, inflammation, and skin rashes for domestic animals and humans.
They can also be fatal if eaten by a pet, and were officially deemed a harmful species in France in a decree dated April 27, 2022.
They can be recognised by their movement in ‘single file’ long lines (‘processions’) along tree trunks and the ground, while their nests look like large balls of cotton wool in trees.
There are two main species in France. Pine caterpillars (chenille processionnaire du pin) are mainly seen in the south, centre and west of France between January and May, with a spike in March.
Oak caterpillars (chenille processionnaire du chêne) are mainly found in the north-east, the Paris region and the north-west of France between April and July, however residents in the north of the country are already spotting the creatures - two months earlier than usual.
Present across the country
In Saint-Malo (Ille-et-Vilaine), the caterpillars have already poisoned several dogs in parks, particularly in the Cité d'Alet, reports local media, Le Pays Malouin.
Further south, the Var Prefecture also confirmed the species is “already back again” in a warning posted on social media on February 1.
The town of Vichy (Allier) has experienced problems with the caterpillars for several years and in 2026 plans to invest €15,000 to help to reduce their number and danger by installing 125 traps and destroying nests, reports La Montagne.
Action is also being taken in Bourg-en-Bresse (Ain) where 277 nests have been destroyed so far this year, compared to 185 in 2025.
Some communes in the Nouvelle-Aquitaine region are once again handing out ‘eco-traps’ this year, designed to be attached to trees to capture processionary caterpillars as they make their way from their nests to the ground. Traps are also offered for trapping Asian hornets.
These can be collected for free upon showing proof of identity and address at La communauté d'agglomération Royan Atlantique (Cara) headquarters every Friday morning until the end of this month. See here for more information.
Early action is key to slowing the spread and reducing risks.
What should you do upon seeing the caterpillars?
Members of the public are warned not to try and kill the insects - as this could be more dangerous and environmentally damaging - and instead to avoid them as much as possible.
To avoid an allergic reaction, people are also advised to:
Wear long clothing when walking in the forest or near infested trees
Avoid rubbing your eyes during or after a walk
Take a shower and wash your clothes above 60°C if you suspect exposure to caterpillars
Symptoms of irritation (including in pets) are:
Painful, severely itchy rash within eight hours of skin contact
Conjunctivitis (red, painful, watery eyes) within one to four hours in case of eye contact
Sneezing, sore throat, difficulty swallowing and possibly breathing difficulties if inhaled
Hypersalivation, vomiting and abdominal pain if ingested.
Any pets or infants thought to have been exposed to the caterpillars should be taken to a medical professional immediately, says the Agences régionales de Santé (ARS).
People across France are also urged to report sightings of pine and oak processionary caterpillars via the dedicated government app or website.
