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Moth of the Week

Purple Thorn

Selenia tetralunaria

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The purple thorn (Selenia tetralunaria) is a moth of the family Geometridae. The species was first described by Johann Siegfried Hufnagel in 1767.

Description This moth’s wings are mainly a darker brown with a lighter brown “termen” (“The edge of the wing most distant from the body”). There is a dark spot at the tip of the forewing and a white crescent shaped mark on all the of wings. There is also a black spot on the upper side of the hindwings.

Adult moths’ sizes can vary due to which brood they are a part of:

Spring Brood: 46 - 52 mm (≈1.81 - 2.05 in)

Summer Brood: 44 - 46 mm (≈1.73 - 1.81 in)

Second generation moths are also different in color. Butterfly Conservation says that are paler while Wikipedia says they are darker.

This moth’s caterpillar is reddish brown mixed with darker brown and gray.

Diet and Habitat This species’s caterpillar feeds on a variety of trees and shrubs such as alder (Alnus), birch (Betula), European ash (Fraxinus), apple (Malus), black poplar (Populus), Prunus, pear (Pyrus), oak (Quercus), and rose (Rosa).

This species is distributed in both Northern Europe and Central Europe. It is scattered in Britain, and it is not found in Ireland. They inhabit woodland, scrub, heathland, and rural and suburban gardens.

Mating In the British Isles, there are two generations a year. The spring brood flies from April to May while the summer brood flies from July to August. In more mild years there can be a smaller third generation that flies in late September and October.

Predators This species flies at night and is attracted to light. No listed protections or specific predators.

Fun Fact The purple thorn is similar to the lunar thorn (Selenia lunularia). They can be told apart because the purple thorn has a dark spot on its hindwings.

(Source: Wikipedia [1][2][3], Butterfly Conservation)