© AVSA 2011-2023 Version 19.1.07 20/01/2023


The pine processionary caterpillar - Be on your guard for these. English: Pine Processionary Moth / Caterpillar Scientific: Thaumetopoea pityocampa Castilian: Procesionaria del Pino.
This is what the nest looks like.
This is what the adult caterpillar looks like.
There are several stages within their lifecycle but they are only dangerous to people and pets during the caterpillar phase, which is usually from January to March. A single female moth can then lay up to 300 tiny eggs which she attaches in a mass to a pine needle. Around one month later these eggs hatch into minute caterpillars. Generally this stage happens around February and March but depending on spring temperatures can begin in January or continue until April as well. This is the time for them to leave the nest in preparation for the next part of their lifecycle, and it is this point when most people and pets come into contact with the caterpillars, sometimes with very painful consequences. The colony follows a leader, nose to tail, in a long procession. These processions can vary greatly in length, depending on how many have survived to this final caterpillar stage and whether they have been disturbed. 60 or so caterpillars each about 4cm long in a chain can be an impressive sight and if seen along a road may be mistaken for a snake. While searching out a pupation site, they may travel a distance of 30 or so metres to find soft soil to burrow into. Once underground they change into pupae and lay dormant until the summer months. If the weather conditions are not favourable, they may remain underground until the following year. This is why some years seem to have many more visible nests than others, it may literally be because two years of moths (this years and last years) emerged at the same time. From the perspective of humans and animals, these caterpillars are only a problem when they are on the pine trees or moving to their new burrow. The caterpillars are covered in tiny barbed hairs which are their defence mechanism. These hairs are often being shed and so can be airborne around infested pine trees, on the branches where they have travelled and also left in the line of the migrating procession. When humans and our pets come into contact with these hairs, they can cause reactions ranging from mild inflammation and irritation to severe anaphylactic shock. The worst problems occur if you make contact with the caterpillar directly and ingest the hairs, either by picking it up, stepping on it or moving them in some manner. Once on your skin a rash soon forms which can be incredibly itchy. Medical advice should be sought if you are unfortunate enough to experience this. The rash can be painful, very itchy and lasts for as much as three weeks. Moving the caterpillars, their nests, or even the branches that they have walked along, may release these hairs into the air where they can be inhaled or come to rest unnoticed on clothing. The nest material that remains on the tree after the caterpillars have left will still contain the hairs. Even burning infected pine branches can result in the hairs being lifted into the air and falling anywhere or being inhaled. If you find that you have an infected tree or trees in your garden, then it is best to contact a specialist, or someone who is experienced in the removal of these creatures. Do not allow small children to approach the caterpillars or their nests. If they occur on your neighbours trees, notify them, and ask that they arrange for their professional removal. Do not attempt to remove the nests or caterpillars yourself, without suitable protection, or experience. It you inadvertently come into contact with the caterpillars, do not touch your eyes or mouth. If you are prone to allergic reactions, seek medical advice immediately. For minor contact, an antihistamine cream may reduce the irritation. The caterpillars are most dangerous to pets. Veterinary services have many emergency calls at the time when the caterpillars are migrating to the ground as inquisitive dogs can get too close to the intriguing procession and may pick up the hairs onto their paws, these irritate and so they lick them. Once the hairs are on the lips/tongue it will induce itching, swelling and possibly vomiting. Look out for the symptoms of small white spots in the mouth and on the tongue, excessive drooling and chomping. In some cases partial amputation of the tongue is the only course of action.