Pine Processionary Caterpillars in Spain: Here’s everything you need to know

Sharing is caring!

The Pine Processionary Caterpillar is feared by dog owners all over southern Spain, and for good reason. These hairy larvae can easily end your dog’s life. But they can also be dangerous to young children and create severe allergic reactions in adults.

After living 8 years in Andalucia and spending a lot of time outdoors, it still baffles me that so many people don’t know how poisonous these creatures are.

At the same time, dogs die every year because they have stuck their nose where they shouldn’t have, and I talk to people who got an allergic reaction from coming in contact with them.

That’s why I’ll explain everything you need to know about Pine Processionary Caterpillars, when and where you can expect to see them, and what to do if you or your dog gets in direct contact with them.

Pine processionary caterpillars

What are Pine Processionary Caterpillars

Pine Processionary Caterpillars are usually around 3-4 cm long, with a warm yellow, orange, or brown color. Their bodies are covered in millions of hairs which function as tiny poison arrows to protect themselves.

They spend their first living weeks in white spider-web-like nests in pine trees. Once they crawl down to the ground, is where you mostly will see them either still in a crowd regrouping or walking in a line, sometimes up to 2 meters long.

This is why they are called processionary caterpillars. They will walk in a line until they find a suitable place to crawl underground. After a few months underground, they turn into moths and fly out, usually in autumn.

Also known as the pine processionary moth, they will eventually fly up in the pine trees and lay their eggs. Each individual can lay around 300 eggs in a sticky mass which is fastened to a pine needle.

Once the baby caterpillars are born, they build a nest which they use as a base while foraging on the pine trees until they are big enough. Monitoring of pine processionary caterpillars have shown that they travel long distances at night to feed on pine trees far from their nests, even in freezing temperatures.

Once they’re done growing is where the life circle starts all over again by crawling down of the pine tree and looking for a nice spot in the soil to dig themselves down and form cocoons.

The pine processionary caterpillar don’t have many predators, but there are a few bird species that enjoy them for a snack. Luckily for the pine forests, which are suffering when large numbers of pine processionary caterpillars devour their pine trees.

processionary caterpillar nest
processionary caterpillar nest

Where can you find processionary caterpillars in Spain

You can mainly find processionary caterpillars in Spain in the southern Mediterranean areas including the islands where ever there are pine trees. Not only in pine forests, as the pine processionary month even lay eggs in pine trees in inhabited areas like gardens and golf fields.

If you detect nests in your garden, do not try to remove them yourself as it can result in their tiny poisonous hairs flying around and creating more harm than good. Call local authorities or pest control so that you know they get removed in a safe way.

pine processionary moth nests
pine processionary moth nests in the pine trees

When can you expect to see processionary caterpillars in Andalucia

After the nests are built, it usually takes two to three weeks before the pine processionary caterpillars come out. Yet, they usually don’t come out if it’s too cold. That’s why you often see them earlier on eg. Costa del Sol where the winter is warmer compared to higher areas in the inland where minus degrees are common at night.

Yet the season for the pine processionary caterpillars to move out from their nest is anywhere between late December to March, usually seen until summer.

Every year I meet surprised hikers with their dogs running around the pine forests on the coast, when I mention that I’ve already seen them out on the path late December or early January.

It seems like people don’t want to accept the fact that they come out this early. Because they’re “meant to come out in February-March”. Sorry to disappoint! That’s not the reality. At least it hasn’t been for the last 8 winters.

Yet, in the colder areas and higher mountains, they often come out later. Though I did see them out at nearly 1800 m of altitude in Sierra de Cazorla in December.

If you’re normally hiking with dogs, you might just want to leave them at home whenever you hike a place with pine trees with nests any time from the end of December and until summer.

If the nests aren’t built yet, it means they haven’t started their foraging yet and you can safely bring your furry friend.

Processionary caterpillar group
Pine Processionary Caterpillars regrouping

Why are pine processionary caterpillars dangerous?

As I mentioned above, the pine processionary caterpillars are covered in millions of hairs that work like tiny, poisonous arrows. They contain a protein called Thaumetopoein, which in small doses can create a rash that is similar to what you get when stung by a nettle.

When they protect themselves, they dart out these toxic hairs which in turn can get stuck in your skin, eyes, or in your pet’s skin or fur – which they are likely to lick thus transfer to their tongue.

Worth noting, is that these hairs are poisonous even after the caterpillars are dead. It’s common to see lines of them ran over by cars on the roads, so you need to take care so your pet don’t walk on them.

It’s also common that venomous hairs are left behind wherever the caterpillars have passed on the ground. You or your dog could just as well walk in those.

Typical symptoms to look for on your dog – unless you actually witness that it is in touch with the insects:

  • small white spots around their mouth and tongue
  • drooling
  • swollen tongue
  • vomiting
  • suffocation
  • disorientation

You might also notice that your dog is itching or trying to lick off the pain on the affected area intensively.

Common reactions in humans are allergic reactions and respiratory problems, which makes it especially dangerous for small children. When caterpillar hairs are in contact with the eyes, it can even harm your sight.

Some people react mildly, while others have a stronger reaction. It’s not unheard of that people have gotten an arm or a leg blow up to double the size due to an allergic reaction.

The potential danger of pine processionary caterpillars should not be underestimated.

Processionary caterpillar nest
Processionary caterpillar nest

How to protect your dog against pine processionary caterpillars

The only way you can safely protect your dog from pine processionary caterpillars, is to avoid taking it to pine forests with nests from the end of December until summer.

However, if you choose to take your dog until you actually see them, or if you live in an area with a lot of pine trees with nests, you can ask your vet for pills to slow down a potential allergic reaction.

Nearly every year, I see pine processionary caterpillars on a hike when I walk with Ayla (my ever faithful furry friend) – very early in the season before I expect to see them.

Whenever this happens, I keep her on a short lead next to my leg and browse the ground while walking so I make sure that she doesn’t walk or stick her snout on any.

I usually wash her paws when we get home too. Not sure if it actually makes a difference to wash her, but I hope it removes any caterpillar hair she might have stepped on so she won’t try lick them off. I’d rather be safe than sorry.

Another thing to keep in mind, even though you leave your dog at home for the hike, is that if you step on the caterpillars, you will have your shoes full of hairs. Shoes that you bring home and walk on the same ground as your dog. If your dog gets stung on the paw, there is a big chance it’ll lick it. So clean your shoes too or leave them in a secure place where your dog won’t get in touch with them.

Stepping on the caterpillars can also result in venomous hairs flying in the air which in turn can get stuck on you or anyone around you, including pets.

Hikes in Andalucia without pine trees:

YOU MIGHT ALSO LIKE: Essensial tips you need to know about hiking with dogs

What to do if your dog licks on a pine processionary caterpillar

If you have pills given by your vet, make sure you give them to your dog the same moment you realize it has been licking or eating on the caterpillars.

You still need to hurry to the vet as soon as you notice your dog has been in contact with the larvae or notice any of the earlier mentioned symptoms.

Giving this pill is no guarantee that your pet will survive – especially if it eats or lick the caterpillars – but it might buy you a bit more time to reach the vet.

According to my vet, washing the affected area with cold water (which you’ll have with you on a hike anyway) might also help slow down the reaction.

In any case, make sure you get to the closest vet as soon as possible for treatment as the sooner you get there, the better chances your pet has to survive.

Caterpillars outside their nest

What to do if you get in direct contact with a pine processionary caterpillar

As I mentioned above, different people react in different ways when being in touch with the pine processionary caterpillar.

If you only get a mild reaction with a rash, it can often be enough with an antihistamine cream. But if you swell up, the pain is very strong, or you notice respiratory problems, you should definitely seek a doctor as soon as possible.

If your child gets in touch with the pine processionary caterpillar, make sure you go to a doctor straight away. If the child has touched his or her mouth with an infected hand or put a caterpillar in the mouth, make sure you call the emergency number (122) directly so you can talk to a professional while you wait for the ambulance so you can get the right guidance.

If you have small children, teach them at an early age not to touch these creatures and to tell an adult if they see them.


The pine processionary caterpillar is probably the only creature in Andalucia that is a true threat to pets and small children. I might be a bit over-protective with Ayla when it comes to them but I find them rather scary and definitely don’t want to gamble.

Yet, I think it’s important not to let them scare you away from hiking and enjoying the outdoors. Make sure you respect them and take the right measures for whenever you go in their territory when they’re out on their processions.

If you live in southern Spain, make sure you spread the information so that more people are aware of the dangers of these small insects.

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.