Purple thorn
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Insecta
Order:	Lepidoptera
Family:	Geometridae
Genus:	Selenia
Species:	S. tetralunaria
Binomial name
Selenia tetralunaria (Hufnagel, 1767)

The purple thorn (Selenia tetralunaria) is a moth of the family Geometridae. The species was first described by Johann Siegfried Hufnagel in 1767. It is a species of both Northern Europe and Central Europe. It has a scattered distribution in Britain but is absent from Ireland.

This species is dark purplish brown, paler towards the termen, with a dark spot at the apex of the forewing. Both wings are marked with a comma-shaped white mark. The margins of the wings are angular, giving the species a distinctive shape. Two broods are produced each year and they differ considerably in size and colour. Adults of the spring brood, which fly in April and May, have a wingspan of 46–52 mm. Moths of the summer brood, flying in July and August,^[1] are smaller (wingspan 44–46 mm) and darker. The caterpillar is reddish brown, mottled with darker brown, and with pale greyish.

The species flies at night and is attracted to light.

The caterpillar feeds on a variety of trees and shrubs (see list below).^[1] The species overwinters as a pupa.^[2]

1. ^ The flight season refers to the British Isles. This may vary in other parts of the range.

• Alnus – alder
• Betula – birch
• Fraxinus – European ash
• Malus – apple
• Populus – black poplar
• Prunus
• Pyrus – pear
• Quercus – oak
• Rosa – rose

• Chinery, Michael (1986, reprinted 1991). Collins Guide to the Insects of Britain and Western Europe.
• Skinner, Bernard (1984). The Colour Identification Guide to Moths of the British Isles.

Wikimedia Commons has media related to Selenia tetralunaria.

• Kimber, Ian. "70.239 BF1919 Purple Thorn Selenia tetralunaria (Hufnagel, 1767)". UKMoths. Retrieved 5 July 2019.
• Fauna Europaea
• Lepiforum e.V.