The Gatekeeper, also known as the Hedge Brown, is a golden butterfly that provides a welcome sight in the middle of summer, when the fresh adults start to emerge. This butterfly spends much of its time basking with wings open, when the sexes are easy to tell apart - only the male has the distinctive sex brands on the forewings. In England and Wales this common and widespread species is found south of a line between Westmorland in the west and South-east Yorkshire in the east. In Ireland it is confined to coastal areas of the south and south-east counties. The butterfly is also found in the Channel Islands, but is absent from Scotland and the Isle of Man. The habitat this butterfly requires is found over most of the British Isles, and so we can only assume that the restriction to its range is governed primarily by climate. Colonies vary greatly in size, depending on the available habitat, ranging from a few dozen individuals to several thousand.
Pyronia tithonus ssp. tithonus
The species was first defined in Linnaeus (1771) as shown here (type locality: Germany). The nominate subspecies is not found in the British Isles.
Pyronia tithonus ssp. britanniae
This subspecies was first defined in Verity (1915) as shown here (type locality: England). The population in the British Isles is represented by this subspecies.
There is one generation each year, with adults emerging in July, peaking in early August, with only a few adults remaining until the end of the month. In contrast with its close relative, the Meadow Brown, this butterfly has a relatively-short flight period.
The chart(s) above have been correlated with the phenology plot below, taken from the UK Butterfly Monitoring Scheme. The blue line gives average counts over the full data set from 1976 to date, and the red line gives the average for the last year.
This species can be found wherever shrubs grow close to rough grassland. In fact, some of the largest colonies can be found at field edges and along hedgerows and we can expect to find this butterfly in scrubby grassland, woodland rides, country lanes, hedgerows and the like anywhere within its range.
Males set up small territories, often centred on a particular shrub or bush, and will fly up from their perch to investigate passing butterflies in the hope of finding a mate. Pairing occurs without any obvious courtship and, once mated, a female will typically lay between 100 and 200 eggs.
Although both sexes feed from honeydew, they will also feed from whatever nectar sources are available - Bramble and Ragwort being particular favourites.
ab. pallidemarginata (Oberthur.Lep.Comp.1909.3.p.389.)
The ground colour normal with the margins pale instead of brownish, but the apical eye remaining black with a white pupil. Similar to albinotica Goodson which however has the eye-spot lacking in black pigment. Oberthur's form is not an albino.
Eggs are laid singly, usually in shade underneath a shrub, either on the foodplant, on nearby vegetation or at random - ejected into the air over a suitable patch of foodplant. Eggs are pale yellow when first laid but soon develop brown patches, giving a mottled effect. They darken further as the larva develops within the egg. This stage lasts between 2 and 3 weeks.
The larva eats its eggshell on hatching and proceeds to feed on the tenderest parts of the foodplant by day, before hibernating after its first moult at the base of a grass clump, usually within a withered grass blade. Larvae resume feeding in the spring and typically only feed at night. There are 2 colour forms of the larva - light brown and green and there are 4 moults in total.