Processionary caterpillars are more numerous in Monaco this year and pose a direct threat to humans and animals, particularly dogs.

Up to four centimetres long, with a body dotted with red spots and a yellow belly, they are covered with allergenic bristles.

The animals live in pine trees but at this time of the year they leave the trees to burrow underground for up to three years. They should not be touched.

A particular menace for passing dogs, the bristles transmit a poison that infects the tongue, and if left untreated this can be fatal. If a dog starts drooling or foaming at the mouth it should be taken to a vet as an emergency.

A total of 180 pine trees in the Principality have been sprayed with Thuringian Bacillus, which is a natural insecticide for the destruction of caterpillar, but which is harmless to humans and dogs.

Cap d’Ail has experienced a major outbreak and has taken strenuous measures to deal with the problem.

The advice for dog walkers: Keep the animal on a leash and avoid pine trees.