The gatekeeper or hedge brown (Pyronia tithonus) is a European species of butterfly. Given its preference for warmer weather, the restriction of range expansion can be assumed to be due to climate. Colonies vary in size depending on the available habitat, and can range from a few dozen to several thousand butterflies. Similar species and subspecies It is a member of the subfamily Satyrinae in the family Nymphalidae. A similar species is the meadow brown; the two species can be difficult to distinguish with closed wings, since the underwing markings are very similar. However, the gatekeeper tends to rest with its wings open, whereas the meadow brown usually rests with its wings closed. The gatekeeper is also smaller and more orange than the meadow brown and has double pupils on its eyespots. Two other similar species of Pyronia are found in southern Europe, the southern gatekeeper (P. cecilia) and the Spanish gatekeeper (P. bathsheba). P. tithonus has two known subspecies. P. t. ssp. britanniae, defined by Ruggero Verity in 1915, is represented in the British Isles. P. t. ssp. tithonus, defined by Carl Linnaeus in 1771, is not found in the British Isles. Instead, this subspecies is seen in central and southern Europe except southern Italy and in the Mediterranean islands except for southern Corsica and Sardinia. Physical appearance The gatekeeper is orange with two large brown spots on its wings and a brown pattern on the edge of its wings. The eyespots on the fore wings most likely reduce bird attacks, therefore the gatekeeper is often seen resting with its wings open. A large number of aberrant forms are known, such as excessa, where specimens have two to four extra spots on the fore wing upperside. The number of spots on the hind wing underside also varies. Sexual dimorphism The male has a dark patch on the upper side of the fore wing that contains scent-producing scales known as the androconia. This is most likely for courtship purposes. Androconia have evolved through sexual selection for the purpose of releasing pheromones for attracting mates. Little is known about how androconia actually function during courtship, and the chemical composition of the pheromones is unknown. Females typically have more spots than males. Males have more costally placed eyespots, compared to the females, whose eyespots are more spread over the wing margin. Distribution As indicated by its alternate name, the gatekeeper butterfly prefers