16 Mar, 2007 @ 10:51
3 mins read

Danger! Caterpillars crossing

thaumetopoea pityocampa

Jason Heppenstall

If you go down to the woods today you might just be in for a big surprise – especially if you have a dog. There lurks, in pine forests around the region, a very nasty creature that has such an effective means of self defence it is more akin to chemical warfare. The little beast to which I allude is the dreaded processional caterpillar (Thaumetopoea Pityocampa) – a pest so rampant and hazardous that the environmental branch of the Guardia Civil (Servicio de Protección de la Naturaleza) can be called out if you have them on your land and you want to get rid of them.

“Bastards!” says Dave Shaw, an estate agent who recently took his four dogs for a walk above Carataunas. “The dogs were running around and picking up sticks and generally behaving like dogs will in a forest. But on the way home in the car three of them began to vomit and one, a puppy, was seriously sick for fourteen hours” Dave took the animals to the vet, who quickly realised what had happened. The dogs had come into contact with a column of processional caterpillars. In the worst case one dog, Chester, had taken one into the mouth; as a result the dog lost two pieces of tongue and is lucky to still be alive. “The vet said that in some cases the tongue has to be amputated or it will wither and die.”


So what exactly is a processional caterpillar? The species is common throughout the Mediterranean and lives in pine trees at any altitude. You may have seen their silky cocoon-like nests in the branches and wondered what they were. Inside each nest there can be hundreds of baby caterpillars which, during the spring months, hatch out and fall to the ground. They roam around in long columns, ‘nose to tail’, hence the name, and move from tree to tree, stripping it of its foliage.

“Don’t go near them!” warned Steve Lee who runs a health food shop in Órgiva and had a recent brush with the processional caterpillar. Steve noticed several nests in his garden and, concerned for his animals, attempted to eliminate them. Already aware of the dangerous poisonous spikes on the caterpillars’ bodies, Steve was taking no chances when it came to getting rid of them. Using sticks he manoeuvred the caterpillars into a bucket and then emptied them onto a roaring bonfire and stood back. So far so safe, you might think. Not so.

“What happened next,” Steve related “was the fire sent a cloud of poisonous fine spines into the air, mixed in with the smoke. These then rained down on me and caused a terrible skin reaction.” Several weeks later Steve is still showing signs of the “incredibly itchy” rash that developed on exposed parts of his skin. “They’re ‘orrible.” Added his wife, Audrey.

Just how dangerous can these caterpillars be? Dave Shaw told me that this years’ outbreak is the worst in years and that three dogs have reportedly died in Cadiar alone in recent weeks. “Even worse,” he says “I heard reports that a young girl in Mallorca had come into contact with them and suffered a violent anaphylactic shock reaction from which she died. People have got to know about the dangers of walking in pine forests around here in the spring.”

I wonder how one might safely get rid of them. One supposedly recommended method is to spray the caterpillars nest with hairspray, wrap it in a plastic bag and torch it. I wouldn’t recommend this method though as it would seem to pose a high risk of starting a forest fire. By no means hit the caterpillars with a stick or stamp on them because this will just send their spines into the air in a kind of toxic dust cloud that can be inhaled. No, the best advice I have come across for dealing with them is to simply steer clear of them. They are active and dangerous between the months of February and May, and colonise pine forests or individual pine trees. After this time they turn into moths and are harmless. If you simply have to walk in the woods around this time the official advice is to carry some antihistamine tablets with you.


If you have any in your garden you can call Seprona on 062 and ask them to come round and deal with them. Another method is to purchase a hormone trap which, very basically, emits a hormone that makes all the male caterpillars smell like females. The resulting orgy of confusion means there won’t be many babies produced and the colony will die out. These traps can be purchased from www.exosect.com

A popular method of control is to destroy the nests during winter (i.e. before January) by blasting them out of high branches with guns. Again, I wouldn’t advise this unless you really detest your neighbours who are downwind of you.

So is there anyone out there who regards the processional caterpillar as a cute furry friend? Steve knows of someone. “They came in our shop once and said they had seen a column of processional caterpillars under attack by an army of ants. So what did they do? They drove the ants off with sticks and helped the caterpillars reform their broken column.”

It’s heart warming to know that someone out there cares.


  1. Just to clarify a little the article above

    “hundreds of baby caterpillars which, during the spring months, hatch out and fall to the ground.”

    In reality, the caterpillar has stages called “instars” and at the beginning of each “instar” it sheds its old skin and grows in size

    At about this time of year (spring) the 5th “instar” caterpillars start to drop off of the pine trees and form the familiar processions. What they are actually doing is looking for some soft ground to burrow into so that they can Chrysalis until the temperature and other conditions are right for hatching into moths.

    As far as I know they can stay in the ground for a few years like this and I think that the ones that come out from the ground as moths are not necessarily from the previous years processions.

    To break the cycle the caterpillars need removing when they are very small in the tree nest or destroying whilst in procession mode on the ground.

    Clive (wildside)

  2. hi, I have been attacked by these little bstds!!
    I went to my cortijo which is underneath a pine forest and found all of these caterpillars in the porch all over the place, so I didn’t want to step on them thinking oh nice little monarch butterflys later! so I swept them up and chucked them in the land. then about 10 mins later I started to itch around the neck. the next day my neck, chest back of neck, parts of my arms and hands were swollen,red, itchy as hell. like I had been bitten by fleas, I went to the pharmacy got antihistine. now 2 days later the itching hasnt stopped its unbearable. does anyone know how long this lasts??? help!! I have put up signs on posts telling people not to go up into the forest and why and telling them its dangerous for dogs , told the ayudamiento but they haven’t taken it seriously. will tell the school as well to inform them of it so they can warn the kids. horrible little things and they look so cute!!!! I look like I have the chicken pox and man its itchy as hell!!! help!!!!!!

  3. Stay away from them, any pets will be in grave danger if they ingest the hairs, and humans alike.

    The best way to get rid of them is to squirt diesel on the cocoon, if accessible.

    I found anti hay fever tablets work for the itching.

    Also, any pine cones found at the foot of the trees should not be used as fire starters / kindle, as they may contain the caterpillars which can give off toxic fumes, there have been deaths reported in spain due to their use in this way.

  4. we have a lonesome pine by our swimming pool, myself and my husband have been attacked by, what we thought may be midges, but obviousoly not, neighbours have complained, and we have had to by antihistamine tables, as i killed some with bleach, and the spines are still floating in the air. Some of these spines have caught in washing, and attach the body after wearing, if this happens to you call the coucil, or urb. office.

  5. Anyone planning to go trekking in the natural and national parks of the Sierra Nevada: beware! There seems to be a lot more of the candy floss-like “nests” in the pines this year; and the amount of processions I saw just yesterday, I would compare to a Madrid rush hour at the start of a puente long weekend! Do not worry the caterpillars and keep dogs at a distance – curiosity can also kill canines.

  6. I keep reading about the processionary caterpillars, and hearing about them on the radio, and in fact I saw them on the move once, near Lanjaron, but nobody ever says what they will turn into, and why they need to be so virulent. Also, once they start to “proceed”, how far can they travel? If they’re only on the move one day a year, for instance, we can just keep our animals away from the pines that day. There is one pinetree by my spring, with one cocoon, which I pass with my dogs and cat most days.

  7. Hi Stephanie,

    Please read the second and third comment made on this article (above)… You will find, in the second comment, a link to a lot of in depth information and discussion at the iberianature forum and in the third comment there is a basic description and you will see that the caterpillars are a larval stage of moths…

    The time the caterpillars are on the ground searching for somewhere to pupate lasts many weeks as the nests in lots of trees hold caterpillars of different ages and some leave the trees later than others…. It’s not just for one day… As to your question about distance, it is generally a maximum of 30 metres from the host tree before the caterpillars find suitable ground to burrow into for pupation..

    If there is only one nest in your pine tree then ask someone for advice as to how to get it removed because in the nest there will be upwards of 300 caterpillars and they will all turn into moths, lay eggs and start the cycle again.

    I hope that helps


  8. They happen in France too. I have had two processions across the car park in my garden. I have several pine trees in my garden and they probably come from them. We used to remove the nests when the trees were small but now it is impossible.

    The second time I checked with various Websites which gave no effective advice, especially not on a Sunday evening, so got some pyrethrum spray, gave them a good dose of that, and then after five minutes brushed them up very carefully with a small brush and shovel They are currently in a sealed plastic bag in my dustbin.

    This all happened half an hour ago and I am still not itching! So touch wood, perhaps the hairs were immobilised by the insect spray. I have a dog and three cats and did not want to leave the caterpillars to get on with whatever they had in mind. Never a dull moment in this neck of the woods.

  9. Thanks for the comments which I see are from 2009 and back. I live in Galicia next to a pine forest and every year have seen the processionary caterpillars and know that they are dangerous. But this year has been terrible. For the first time we all have itchy rashes around our necks, hands and any other exposed parts that are very uncomfortable. It’s really unheard of. Thanks for the tips and other comments.

  10. I’ve just found and destroyed 2 lines if them without incident or injury!
    Boil up a good amount of sugar,water and the oil from the deep fat fryer (though any would do). Make sure it is scalding hot and sticky and pour over the caterpillars. They die very quickly and the spines stay put.
    I then sprayed them with hairspray, just to be sure. Put gloves on and pick them up with a shovel.
    I then sprayed the ground with mild detergent and washed it all away with the hose under pressure so that the dogs won’t be attracted by the sugar.
    Hope this helps some of you with this problem.

  11. We live on the Costa Blanca with three dogs. The Caterpillars are just about to come out. We use a spray bought from Aldi which is primarily for Cockroaches. It seems to kill them immediately and we don’t seem to get any reaction from the dead caterpillars.I am told that to destroy the nest you should first spray it with hair lacquer cut it out of the tree into a fire bucket whilst wearing goggles, and a mask, pour lighter fuel on it and then burn them. This ensures there is no fire risk. Officially you should call out the Guardia who can’t be bothered.

    Best of luck Mike Robins

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