Purple Hairstreak (Favonius quercus) in Ireland

Ribeog chorcra in Gaeilge. The Purple Hairstreak, Favonius quercus, is a canopy-dwelling species of mature oakwood and is more often seen at binocular range in tree-tops than on ground-level flowers.

Identify it in four steps

1. Males upperside dark brown with a strong purple iridescence across both wings, visible only in fresh sunlight at the right angle.
2. Females upperside brown with a bold purple patch across each forewing, more compact than the male’s overall wash.
3. Underside silvery-grey with a fine white hairstreak line and small orange marks near the tail on the hindwing.
4. Wingspan 32 to 40 mm; flight is a fast, spiralling dash around the tops of oak trees, often at 8 to 15 metres above the ground.

Habitat in Ireland

The Purple Hairstreak is an oakwood species tied entirely to Sessile Oak (Quercus petraea) and Pedunculate Oak (Quercus robur) as larval foodplants. Adults spend most of their lives in the canopy and are best seen on warm still evenings in July and August when they descend briefly to lower foliage or feed on honeydew.

The species is under-recorded in Ireland because canopy behaviour makes fieldwork difficult. Distribution follows mature oakwood distribution, which is concentrated in the southwest, west, and Wicklow.

Where to see it

• Killarney National Park oakwoods, County Kerry: sessile-oak canopy at Muckross and Torc supports well-documented populations.
• Glengarriff Nature Reserve, County Cork: mature sessile-oak canopy with sheltered rides.
• Glendalough Vale oakwoods, County Wicklow: east-coast oakwood populations tracked by transect.

Related species

• Green Hairstreak (Callophrys rubi)
• Brown Hairstreak (Thecla betulae)
• Silver-washed Fritillary (Argynnis paphia)