Guardia Civil warns of danger posed to humans and dogs by processionary caterpillars at this time of year

Guardia Civil warns of danger posed to humans and dogs by processionary caterpillars at this time of year

Image of processionary caterpillars. Credit: Gonzalo Jara/

This is the time of year when processionary caterpillars start coming down from their nests, posing a danger to humans and especially dogs.

The Guardia Civil warned through its social networks this Sunday, March 19, about the danger that processionary caterpillar infestations can pose at this time of the year. The bite of this insect is very harmful to health, especially for children, and for our pets, especially dogs.

In a Twitter post, they wrote: “These days the #procesionaria of the pine tree is appearing. In humans, they can cause irritation to the ears, nose, and throat, but if your dog licks a caterpillar or is stung, it can be seriously injured or even die. Be careful”.

They inhabit silky nests in coniferous forests that have been built high up in pine trees by the larvae. These were laid as eggs by the completely harmless processionary moth Thaumetopoea pityocampa. It is one of the most destructive species to pines and cedars in Central Asia, North Africa, and southern Europe.

The species is notable for the behaviour of its caterpillars, which hibernate in tent-like nests usually high in pine trees but occasionally in cedar or larch. It is one of the few insects where the larva develops in winter in temperate zones.

These pests can often be seen marching in single file to feed on the needles dropped by the trees. There are often several nests in a single tree. When they are ready to pupate, the larvae march in their usual fashion to the ground, where they disperse to pupate singly on or just below the surface

They subsequently proceed through the woods in what looks like a furry snake but is in fact a line of caterpillars, nose to tail. Lengthy processions are formed when fully grown caterpillars abandon their host tree in search of pupation sites.

As many as three hundred caterpillars may travel long distances from the natal tree looking for soft soil in which to bury themselves and form cocoons.

Processionary caterpillars are covered with stinging hairs that detach and float in the air and can cause ear, nose and throat irritation in humans, as well as severe allergic reactions. The hairs contain an irritant chemical called thaumetopoein, which gives them this stinging ability.

Dogs will often be inquisitive when they spot this moving line on the ground but any attempt by your pet to put its nose near to, or lick these creatures, could have dire consequences in some instances.


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Written by

Chris King

Originally from Wales, Chris spent years on the Costa del Sol before moving to the Algarve where he is a web reporter for The Euro Weekly News covering international and Spanish national news. Got a news story you want to share? Then get in touch at