on or just below the surface. The moth's pupal stage occurs in a white silken cocoon under soil. The pupae measure around and are a pale brownish-yellow that changes into a dark reddish brown. As an adult, T. pityocampa has predominantly light brown forewings with brown markings. The moth's hindwings are white. Females have larger wingspans of , compared to a male's . Adults only live for a single day, when they mate and lay eggs. How far they are able to spread depends on how far the female is able to fly during her short time as an adult. Her average flying distance is , with a maximum recorded of . Behaviour Shelter building T. pityocampa is highly social. Throughout its life cycle, an individual makes several shelters, possibly for protection from predators; the larvae emerge to feed at night. The first of these is flimsy and temporary, but in the third instar, they build a permanent nest. Once the permanent nest is built, the caterpillars become foragers, staying in the vicinity of the nest. The nest has no openings, so caterpillars force themselves through the layers of the shelter. The waste from the larvae's diet falls as frass and accumulates at the bottom of the nest. Processions Lengthy processions are formed when fully grown caterpillars abandon their host tree in search of pupation sites, when 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. During processions, stimuli from setae on the tip of the abdomen of the caterpillar in front serve to hold processions together, taking priority over the trail pheromone or silk. Parasites, predators, and diseases The species is controlled to some extent by predators, parasites and viruses which attack the moth at many stages of its life cycle. For example, eggs are eaten by the orthopteran Ephippiger ephippiger, while larvae are eaten by birds such as great tit (Parus major) and great spotted cuckoo (Clamator glandarius). Larvae are parasitised by solitary wasps (Ichneumonidae, Braconidae) and some species of flies (Tachinidae), and may be infected by the processionary moth virus Smithiavirus pityocampae. Pupae are eaten by hoopoes (Upupa epops), while adults are eaten by bats. Interactions with humans Skin and eye irritation In the third and subsequent instars of their development, pine processionary caterpillars defend themselves from predators with conspicuous