Favonius quercus (Linnaeus, 1758)

Description: Wingspan 33-40mm. Adults have a dark upperside to the wings with a purple metallic sheen. In the male this extends over almost the entire surface of both wings. In the female the purple sheen is only at the base of the forewing and otherwise the wings are black. The underside in both sexes is pale grey with an orange eyespot near the small tail.

Key Identification Features:

• When seen this butterfly is unmistakable but the challenge is getting an adequate view as adults normally stay high in the tree canopy.
• The purple coloured upperside and the pale grey underside are unique amongst Irish butterflies.

Sets:

Flight Period: Single-brooded, July to early September

Status: This is one of the rarest butterflies in N. Ireland, though this is perhaps exaggerated by its elusive habits. It was first found in N. Ireland in the late 19th Century but there were no further reports until it was discovered at Crom in Fermanagh in 1983. It is now known to be widespread in the oak woodland at Crom and has also been found at two other sites, Correl Glen in Fermanagh and Ness Wood in Londonderry. Other colonies probably await discovery.

Ecology: The Purple Hairstreak is a colonial, arboreal species confined to oak woodland. Adults fly around the crowns of oak trees and are generally difficult to observe. Late afternoon and early evenings, or after heavy rain are often the best time, as insects can come down from the treetops. Males will chase females. Females are most often observed at close quarters especially when egg-laying. The adults feed mainly on honeydew, but have been recorded on flowers especially after heavy rain.

World Distribution: southern and central Europe to southern Scandinavia; North Africa, Asia Minor and the Caucasus.

Bradley & Fletcher number: 1557 Agassiz number: 61.004

Additional information:

UK Butterflies account

Caterpillar: