As some of you might know I’m on Twitter quite a lot, mainly following other people who post about nature and history here in the north of England. Today I saw the following video of a kaleidoscope of Green Hairstreak butterflies filmed by Dinesh Patel (@lancsgp) and was inspired to write about this beautiful species, which is unique in the British isles in being our only green butterfly.
The Green Hairstreak is a bright emerald green and has the scientific name Callophrys rubi, Callophrys meaning ‘beautiful eyebrows’, referring to the graceful sweep of the white streak on its wings, and rubi coming from ‘rubus’ which is the scientific name for brambles which are one of its preferred food plants.
It is a medium-sized butterfly, 26 to 34mm wide, and almost always seen perching with its wings closed, the metallic green underwings blending in perfectly with the bright green leaves of spring foliage. This green is edged with orange/brown and otherwise only punctuated by a faint white streak a short distance in from the edge of the wing. The extent of this white, hair-thin streak can be variable, often there is only a few white dots and it may even be completely absent.
(Anaxibia)
Green or Brown?
As it usually rests with its wings closed you rarely get to see the top of them, which is a dull-brown, many species rest with their wings open so one could fairly argue that the green hairstreak is actually a brown butterfly, it will rest like this for long periods too, with its wings orientated towards the sun to maximise its exposure and warm itself up.
The males and females look almost identical but if a green hairstreak suddenly leaves its sunny perch to chase after a passing insect which has impinged upon its territory this identifies it as a male, if the passing insect happens to be another green hairstreak a brief, spiralling, airborne battle will ensue where the victor will take over the male’s spot. This action will be followed keenly by the females and the sharp-eyed observer may notice them shifting their position slightly to better watch the duel.
When and Where to see
The Hairstreak’s flight-time is from April to July and they only have one brood a year, they also overwinter as a pupa, unlike other butterflies, hatching in April to get a head start on things.
They are found throughout most of the British isles but are very localised in most areas, forming distinct colonies which can be as small as a few dozen individuals, these colonies will always be in a sunny locale near to where its food plants grow.
Here in the northwest I’ve regularly seen Green Hairstreak at a few sites and have found that they seem to like south-facing areas of moor, in particular where fresh growth of Bilberry and Heather has been stimulated by burning. These include the south-west facing side of Beatrix fell above Dunsop bridge and at High Stephen’s head, both parts of the Forest of Bowland that happen to be where lots of Bilberries can be picked later in the year, another site I’ve spotted them at is Birkbeck Bog in Cumbria which is also heather moorland but i can’t remember if there was much Bilberry there.
(Gilles St Martin)
Wide range of foodplants
As well as heather moorlands they can be found in a variety of other habitats including sunny hedgerows and woodland edges, south-facing banks and scrubby areas of heath. Their larvae also have one of the widest range of foodplants of any British butterfly. These include heather, Bilberry, Gorse and, as can be seen in Dinesh’s video, Willow. The adults also, as their scientific name suggests, have a liking for Brambles and are attracted to Birds foot trefoil and Cottoneaster, the nectar of which the adults, although not normally nectar feeders, will flock in their dozens to.
One slightly unusual location you can find quite a few of them at the right time of year is on Longridge fell, this is at a spot by the side of one of the gravel forestry tracks quite far in where the track splits off towards a dead-end track, here there grows a Cottoneaster bush and they seem to be addicted to the tiny red flowers on it along with many bees. This stretch of track also has a south-facing bank of Bilberry on it which the larvae no doubt feed on and which is a good spot to pick the berries later in the year.
A B-H
Northwest Nature and History 
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