pine processionary caterpillers emerging from their silk like nest

thaumetopoea pityocampa coniferous destructive behaviour woods urticating hairs europe france mediterranean climate tent irritating moth larvae pupa insect dangerous allergic reaction pest rash skin infection forest nature natural infestation seasonal foliage damage wildlife invertebrate harmful nesting environment cocoon allergy control change bug grub contamination bristly leaf summer plant closeup tree pine processionary orange brown blue black stripped hairy caterpillars crawling nest silk threads embedded branches bush caterpillers silken like emerging