The Pine Processionary caterpillar is greyish-brown, with orange and brown hairs covering the back and lighter hairs along the flanks. On each abdominal segment, small mirror-like patches appear from the third larval stage onward — they contain microscopic urticating hairs invisible to the naked eye. Early instars spin discreet pre-nests. It is from the fourth stage onward that the caterpillars build their large, cottony winter nest, clearly visible in pine trees. They live in dense colonies throughout their development. In spring, they descend from the trees in long, unbroken lines — the famous procession — to burrow into the soil and pupate.
Large parts of France and Europe, primarily in the South. The species is gradually expanding northward due to rising temperatures.
Warning: its urticating hairs can cause severe skin, eye and respiratory reactions in humans and animals. Do not approach or touch.