These are in fact caterpillar nests, constructed by the pine processionary caterpillar (chenille processionnaire) larva, who live in large ‘tents’ and march out at night in single file (hence the name) to feed on the pine needles.

At this time of year, we read a lot about Pine Processionary Caterpillars, hairy and dangerous little fellows who can cause severe irritation and allergic reactions in both human and animals who touch them or who come across their hairs, which can also blow in the wind.