Green Hairstreak

Green Hairstreak Callophrys rubi (Linnaeus 1758)

Family: Lycaenidae, subgroup Theclinae (The Hairstreaks)

Description

Header photo by Fearnley

Photo above left by Phil Morgan

Photo above middle by J Bone

Photo above right by Dave Williamson

An unmistakeable bright, metallic green butterfly, unlike any other in Britain. Underwings green, upperwings brown, showing golden bronze when fresh. Always settles with wings closed, showing green, and resembling the bright green spring foliage of bilberry etc, providing excellent camouflage. In flight it appears an inconspicuous, drab, olive green-brown blur, and looks surprisingly small. Male and female are similar in appearance, with ‘tailed’ hindwings not very obvious.

The green, closed-wing view is crossed by a variable curved line of white dots, ranging from a full set across both wings (ab punctata Tutt), to no dots at all (ab caecus Geoffroy). The highly dotted form may be more of a feature of the northern races of the Green Hairstreak than those in the south (Haworth 1973), and, in the experience of the writer, often accounts for 5-10% of Yorkshire individuals. True ab caecus forms (with no dots) are rare, but many entomologists use ab caecus to describe specimens with a single dot as well, and these are much more common, again accounting for some 5-10% of individuals. The distribution of these various forms in the county deserves further study (see p48). Only 15 variations have been described, mainly involving the variable dot patterns. The green colouring may occasionally be brown or show brown areas (ab brunnea Tutt).

Habitat

A species of rough, scrubby grasslands in cuttings, quarries, woodland rides etc, also found on moors, bogs and heaths. In Yorkshire, the butterfly is mainly found on upland moors in association with Bilberry Vaccinium myrtillus. The county’s few lowland colonies appear to use Gorse Ulex spp. and perhaps Bramble Rubus fruticosus. A wide range of other foodplants has been recorded in Britain, but not in Yorkshire, including Bird’s-footTrefoil Lotus corniculatus, Broom Sarothamnus scoparius, Buckthorn Rhamnus catharticus, Common Rock-rose Helianthemum nummularium, Dogwood Swida sanguined etc.

In moorland areas, sheltered, sunny slopes are favoured, particularly where there are ruts, hollows, incised streams, gullies, and nearby walls, scrub or trees on which to perch. Although preferring sheltered sites, in warm still conditions, individuals will range extensively over open moorland where a light growth of bilberry often occurs amongst the heather. Many of our strongest colonies are found where there are large areas of mainly just Bilberry. Bilberry bushes growing in shade, such as in woodland appear to be less attractive. The species also occurs in certain bilberry-rich bogs and mosses as at Malham Tarn (VC64). Colonies at Spurn, on the Wolds and at Strensall use patches of gorse.

Distribution

Very local resident: one brood, (late Apr/mid-Jun). Found mainly in upland moorland areas, it can be seen in reasonable numbers almost anywhere in Britain in a suitable habitat, apart from the very north of Scotland, The Outer Hebrides, Orkney and Shetland.

In Yorkshire good sites are Spurn Point (VC61), Hawnby (VC62), Snailsden Moor (VC63), Ilkley Moor (VC64), and Druid’s Plantation, Near Masham (VC65).

Increasing records of this species in recent years suggest a real increase in abundance, although the lack of previous records could have been due to under-recording in the inaccessible places this butterfly prefers.

In view of the butterfly’s preference for remote moorland locations, as well as its early and inconspicuous appearance, it probably remains significantly under-recorded in the county.

2019 was an excellent year, by far the best in the past 10 years with almost 500 more individuals than the next best year. In VC64 it can be seen almost anywhere where there are areas of Bilberry, and it is worth looking out for it even on very small patches of Bilberry.

Life Cycle

Eggs are laid in the young tips of growing shoots or flower buds of the foodplant and hatch within 7-10 days. Green and yellow larvae are woodlouse-shaped and well camouflaged. They are solitary and cannibalistic. By Jul/Aug they are fully grown and wander away from the foodplant to pupate. Pupae attract ants by making audible squeaks and producing tasty secretions. It is thought that in most cases winter is spent within the shelter of ants’ nests. The pupal stage lasts 8-10 months. The male is highly territorial and will fly aggressively at other insects, often circling away into the sky in an aerial battle, before returning to a regular perch. Courtship and mating occur throughout the flight period and pairs may be seen perched on low vegetation or on the ground. Females are more elusive, travelling more widely in search of foodplants, and settling and crawling on them to find suitable egg-laying locations.

Although a fairly sedentary species, wandering butterflies may sometimes be found many miles from any known colonies, especially in years when populations are high.

The first Yorkshire sightings in 2019 were on 17 April at Kilnsea Wetlands, on Otley Chevin, and on Bingley Moor.

The last Yorkshire sighting in 2019 was on 05 May at Worlds End.

Photo above middle by Jim Dignan

Photo above right by N Fearnley

Status

The species is not under threat.

Aberrations


NF 14/11/20