The Adventures of Django and Arya

Processionary Caterpillars

Caterpillars, harmless little creatures aren’t they? Unfortunately not. The processionary caterpillar (Thaumetopoea pityocampa) is one of the most destructive species to pine and cedar trees in Southern Europe, including Spain and Portugal, as well as in Central Asia and North Africa. In fact, these critters can be found in most areas around the Mediterranean Sea, except Egypt and Libya. As well as the defoliation issues to forestry, they also pose a significant threat to humans and other mammals. Aptly named ‘processionary’, they march nose to tail in a line, protected by their highly toxic hair fibers. Read on to find out more about the processionary caterpillar, and the threat it poses to inquisitive dogs and cats.

During the summer months, the processionary moth lays its eggs high up on pine trees, optimising the hours of sunshine while also offering protection from ground level predators. In order to deceive any flying threats, the eggs are covered with scales that mimic pine shoots. After hatching, the processionary caterpillar larvae gorge on pine needles as they progress through the five stages of their lifecycle.  The nests themselves are globes that look similar to cotton wool or spiders webs, and can be spotted high up on pine trees.

Processionary caterpillar nest Southern Europe

Towards the end of their larval period, the caterpillar’s protective hairs can cause severe irritation to humans, dogs and cats on contact with the skin. When ingested, they result in much more significant problems, and possibly even death in pets. We have sadly heard of this happening many times in The Algarve, Portugal and coastal areas in Spain – the threat of the processionary caterpillar to dogs and cats cannot be underestimated. Even on survival, it has resulted in several dogs losing their tongue or part of their face, therefore it’s absolutely vital to be vigilant.

The caterpillars tend to venture from their nests during the months of January to April, depending on whether or not it’s been a wet winter. If the winter season has been particularly dry, as in recent years, the caterpillars depart the security of their nests to prepare for the next stage of their life cycle – burrowing underground to transform into the processionary moth. This is the final stage of their cycle, and the processionary moth itself is not dangerous to humans and other mammals.


At the moment, there are no treatments available to protect your dog or cat from the poisonous hairs of the processionary caterpillar. If you encounter a nest, it is best for it to be destroyed by professionals due to the intricate and toxic nature of the fibers.

During the winter months, especially January to April, if you’re taking a break Southern Europe, particulary Spain or Portugal, keep your eyes peeled for processionary caterpillars when walking your dog. Look out for any pine trees in your area and avoid being close to them. Often, you will spot fibers from their nests at ground level, which look like giant pieces of cobweb. Take that as a telltale sign to steer clear of that area. If you walk your dog in wooded areas, it’s best to keep them on a lead so that they can’t go off foraging anywhere they may encounter the processionary caterpillar.

So, always be extra vigilant if you are in Southern Europe with your pet dog or cat during the winter, or in any other area with pine and cedar trees and a known processionary caterpillar problem.

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