Hertfordshire & Middlesex Branch

Distribution and Status

The Green Hairstreak is rare in the two counties and is mostly found on calcareous grassland and heaths such as Hexton Chalk Pit, Aldbury Nowers and the Tring Park area. In the last few years, colonies have been discovered in south-western Middlesex, like Hounslow Heath. Reports of sightings on at least two new sites were received in 2019 including Waterford Heath and Dartmouth Park, east of Hampstead Heath. In 2021 there were reports from Alexandra Park, Heartwood Forest and Bushy Park. It does not appear to exist in open areas in woodland like it did in the past

Habitat Requirements

Unimproved grassland, heaths, railway banks, and woodland rides but scrubby plants or hedgerows must be present

Larval Foodplants

Common Rock-rose Helianthemum nummularium, Broom Cytisus scoparius, Dyer's Greenweed Genista tinctoria, Gorse Ulex spp., Common Bird's-foot Trefoil Lotus corniculatus on chalk. [Greater Bird's-foot Trefoil L. pedunculatus, Dogwood Cornus sanguinea, Purging Buckthorn Rhamnus catharticus, Bramble Rubus fruticosus]

Adult Food Sources

Goat Willow Salix cinerea, Bluebell Hyacinthoides non-scripta, Common Bird's-foot Trefoil Lotus corniculatus

Behaviour/Observation notes

Males take up territories around shrubs like hawthorn, in search for females or to chase off rival males. Females tend to fly close to the ground

Life History

Only one generation is produced each year with most specimens emerging in May. Eggs are laid singly on the foodplant and hatch after about ten days. Larvae begin by feeding in buds then the leaves as they grow. Pupae are formed on the ground, often in ants' nests. The ants being attracted by the pupae are thought to carry them to the nests. The winter is spent in the pupal stage