They show up every spring and are a real nuisance for walkers, dogs and dog owners. Maybe you’ve heard of them, maybe you’ve even seen them crawling across the sidewalks in long processions or you’ve spotted the weird cotton-ball style nests in a pine tree somewhere. We’re talking about the “pine processionary caterpillar”, Mallorca’s most dangerous animal. But how dangerous is it really?
What are they? #
The hairy little caterpillars – also called “larvae” - are in their middle life stage in becoming a processionary moth. Being no more than 3 to 5 cm long they can be quite hard to spot when crawling around alone. But once they find each other, they start forming long “processions”, crawling head to tail in a line.
Where are they? #
Wherever you find pine trees, in early spring there is a potential risk of coming across these hairy little beasts, but sometimes they nest in other kinds of trees as well. If you see something that reminds you of a big cotton ball or a “tent” of rolled-up spider web in a tree, that's their nest. When it’s time to leave they crawl down the trunk one after the other in a train-like formation looking for a nice spot to dig down and pupate to enter their next stage in life which is developing into moths. This stage ends later in the summer, when the moths emerge, fly off to find themselves a partner and a nearby pine tree to lay their eggs, and the process starts all over again.
When are they active? #
Normally, processionary caterpillars start crawling down from their trees around February to March, but it all depends on the weather and temperature. In some years they show up as early as January and they can stay active until May.
Why are they dangerous? #
Each caterpillar has about 500,000 little hairs on its body and these function like small poisoned arrows - or else, they might spread through the air. When getting in direct contact with humans or pets, this causes large local skin reactions like rashes or irritation. The little hairs might also provoke allergic reactions bring on swollen eyes and respiratory problems, in rare and especially severe cases even leading to suffocation.
The caterpillars’ hairs get more poisonous over time. Older larvae might even eject hairs when threatened or stressed. The hairs then penetrate and irritate all areas of exposed skin they get in touch with.
What to do if affected? #
If you come into contact with a pine processionary caterpillar, immediately wash the area with plenty of soap and hot water. Hot water helps neutralize the poison and remove the hairs. If the irritation gets worse, consult a doctor immediately.
A potentially lethal threat to dogs #
The caterpillars are especially dangerous to our curious four legged friends, mainly dogs, who might try to get a good sniff of the wooly little fellows or even start playing with them. If they get caterpillar hairs on their paws in the process and these get irritated and start hurting they would most probably start licking, so the hairs will be spread to the mouth. In this case, a dog’s tongue might swell up to three times its normal size, i.e. there is a risk of suffocation and shock – and in some cases even of death.
If you suspect your pet has come into direct contact with a pine processionary caterpillar, rinse the affected body area with warm water and soap. If it’s in the mouth, rinse thoroughly with water and contact a veterinarian immediately. Be sure to protect yourself, especially your hands and face, since the poison spreads easily. Unfortunately, the crisis isn’t over yet since this reaction can lead to inflammations on the tongue and in the throat. In the worst case, the affected tissue could die which, without proper veterinary care, poses a potentially lethal danger to the animal.
What about preventive action? #
There’s not a lot you can do personally. The nests are high up in the trees and can’t be taken down easily though they are sensitive to cold and can be eliminated by breaking the protective web in the fall.
Never try to kill the larvae by stepping on them or remove them in any way, since when feeling threatened they can literally shoot their poisonous “arrows” at you. If you spot a nest on your property, alert the environmental department (Medio Ambiente) at your local town hall and have it removed by them.
As the larvae are considered an economic pest in coniferous forests, the island's Environmental Department takes measures against them in the most heavily affected forest areas, and also in especially sensitive places like popular public parks and around hospitals and schools. Depending on location these measures include the use of insecticides like diflubenzuron, an insect growth regulator, which can be sprayed from aircraft, biological agents like bacillus thuringiensis which kill off eggs and first- or second-stage caterpillars (in autumn), the deployment of pheromone traps or by physically removing the nests. On a forest hike you might have noticed small plastic bags hanging from the pine trees? Well, those are pheromone traps deployed to attract the moths.
Natural Controls #
Although the pine processionary caterpillars are well protected by their poisonous hair, they do have a number of natural enemies like insects, bats and certain kinds of birds, depending on what life stage they’re in. Eggs are eaten by ephippiger ephippiger, a type of cricket, larvae are on the menu for birds like te great spotted cuckoo, and can be parasited by solitary wasps or infected by the processionary moth virus smithiavirus pityocampae which is a kind of horsefly. Pupae are a feast for hoopoes, and the adult moths are prey for bats.
Four Essential Tips #
Mallorca is a wonderful place to visit in spring, and you shouldn’t let these annoying little creatures affect you when it comes to enjoying everything the island has to offer. As long as you know your caterpillar do’s and don’ts, you have nothing to worry about:
- If you’re allergic or particularly sensitive to the processionary caterpillar’s hairs, don’t dry your clothes outside during the most active period. The hairs are spread with the wind and might get stuck in the fabric.
- If you’re really sensitive you might even get a reaction from taking a shower, since during the most active caterpillar period, the hairs can end up in the water reservoirs. This, however, normally only affects those who are really allergic.
- If you’re travelling with your pet, it’s always a good idea to check out where you can find the nearest veterinarian just in case.
- Keep an extra eye on the ground after a storm. Winter storms are a special thing in Mallorca, and if the timing’s bad and the downpour occur when the caterpillars are on their way down from their trees, they might be washed off and floated along. In this case you might come across the hairy fellows far away from any pine trees, and they’re flying (literally) solo.
By Maria Strömqvist
21 October, 2019