Thaumetopoea pityocampa
| Pine processionary | |
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| Pine processionary larvae marching in characteristic fashion | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Class: | Insecta |
| Order: | Lepidoptera |
| Family: | Thaumetopoeidae |
| Genus: | Thaumetopoea |
| Species: | T. pityocampa |
| Binomial name | |
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Thaumetopoea pityocampa (Denis & Schiffermüller, 1775) |
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The pine processionary (Thaumetopoea pityocampa) is a moth of the family Thaumetopoeidae. Sometimes placed in the genus Traumatocampa, it is one of the most destructive species to pines and cedars in Central Asia, North Africa and the countries of southern Europe. The urticating hairs of the caterpillar larvae cause harmful reactions in humans and other mammals. The species is notable for the behaviour of its caterpillars, which overwinter in tent-like nests high in pine trees, and which proceed through the woods in nose-to-tail columns, protected by their severely irritating hairs, as described by the French entomologist Jean-Henri Fabre.
Though most pine processionary moths only live one year, some in high altitudes or more northern areas may survive for over two years. The adult moths lay their eggs near the tops of pine trees. After hatching, the larva eat pine needles while progressing through five stages of development. In order to maintain beneficial living conditions, silken nests are built over the winter. Around the beginning of April, the caterpillars leave the nests in the procession for which the species is known. They burrow underground and emerge at the end of summer. High numbers of adults are produced in years with a warm spring.
The eggs are laid in cylindrical bodies ranging from 4 cm to 5 cm in length. The eggs are covered with scales which come from the female and mimic pine shoots.
The larva is a major forest pest, living communally in large "tents", usually in pine trees but occasionally in cedar or larch, marching out at night in single file (hence the common name) to feed on the needles. There are often several such tents in a single tree. When they are ready to pupate, the larvae march in their usual fashion to the ground, where they disperse to pupate singly on or just below the surface.
Fabre conducted a famous study on the processionary pine larvae where a group of them were attached nose-to-tail in a circle with food just outside the circle; they continued marching in the circle for a week; he described the experiment in his 1916 book The Life of the Caterpillar. The caterpillars may follow a trail of pheromones or silk, but the main stimuli that induce following are from the hairs (setae) on the end of the abdomen of the caterpillar in front. The ant mill is a similar phenomenon.
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Wikipedia