The oak beauty

Description

Biston strataria, the oak beauty, is a moth of the family Geometridae. It is native to Europe, the Balkan countries and the Black Sea region as far as Asia Minor and the Caucasus. The species was first described by Johann Siegfried Hufnagel in 1767. B. strataria is found in a variety of habitats, but is mostly found in woodlands where it rests on the bark of trees, camouflaged by its mottled black and grey wings. The male has feather-like antennae while those of the female are more thread-like. The moth has a wingspan of 40 to 56 mm (1.6 to 2.2 in). The larvae are mainly brown with three lumps near the end of the abdomen. They have evolved to resemble sticks which helps protect them from predators. The larvae feed on many species of trees, but the most commonly used host plants are oaks. It is common throughout Europe, with the exception of the far north and the far south. In the south, its range extends through the entire Mediterranean, the Balkan countries and the Black Sea region as far as Asia Minor and the Caucasus. In the north it reaches the southern Fennoscandia. It is found in the British Isles including Ireland. In July and August, the larvae can be found feeding on various host plants. B. strataria is prevalent in wooded areas including parks, gardens, and other suburban habitats. It is usually found on the trunk of trees where it can blend with its surroundings. Adults emerge in early spring. B. strataria begins its flight period from mid-March to April, which is an early flight period compared to other moth species. B. strataria usually flies at night and is readily attracted to light. Its mottled appearance aids in its concealment from predators when it rests on tree trunks during the day Although the adult camouflages well with its surroundings, predators may occasionally spot the moth. In these circumstances the moth has one last defense mechanism its hindwings, which were previously hidden in the resting position, carries shocking markings which may warn off predators when suddenly exposed. The oak beauty caterpillar is brown, marbled with white, and has two small red lumps on the back of its eighth, ninth and twelfth segments and a small lump on the belly on the seventh, eighth and ninth segments. The caterpillar's head is slightly notched in the middle, possibly due to evolutionary pressures to resemble twigs in appearance.