Holly Blue Lycaenidae

Celastrina argiolus (Linnaeus, 1758)

Description: Wingspan 26-34mm. Males have lilac-blue upperwings. The outer fringe of hairs is chequered black and white. The underside is pale silvery blue with black spots. Females differ from males in having a broad black border to the upperside of the forewings.

Similar Species: This should be easily recognisable as it is the only blue likely to be seen in woodland. The lack of orange spots on the hindwing also instantly tell it from the Common Blue the only similarly-coloured species in N. Ireland. The two species occur in different habitats and there is little overlap in flight period.

Key Identification Features:

Sets:  male upperside male underside female upperside female underside

Flight Period: In N. Ireland the Holly Blue is univoltine flying from early April to June. In the south of Britain and Ireland the Holly Blue is bivoltine and this habit is apparently spreading north at least in Britain. The second brood flies from late July to September.

Status: In N. Ireland the Holly Blue is confined to central and south Down especially in a triangle betweeen Newcastle, Carryduff and Comber and also the Rostrevor area. There have been records from several other areas but the only confirmed colony outside Co. Down is at Correl Glen in Fermanagh.

Ecology: Colonies of Holly Blue are found in open woodland, hedgerows and mature gardens which support its foodplants. In Britain and Ireland the principal foodplants are Holly Ilex aquifolium and Ivy Hedera helix. The spring brood feeds principally on Holly and the second brood mainly on Ivy. In N. Ireland where all populations are univoltine, Holly is probably the sole foodplant. The females lay eggs at the base of base of flowerbuds on plants growing in sunny warm conditions. The larvae feed on the developing flowers and fruit. It overwinters as a pupa.

World Distribution: The Holly Blue is a very widespread Holarctic species and is present in the whole of Europe except most of northern Scandinavia, North Africa, Asia Minor and Central Asia, China, Japan and N. and Central America.

Bradley & Fletcher number: 1580 Agassiz number: 61.012

Additional information:

UK Butterflies account


 Thompson, R. S. & Nelson, B., 2003 (Oct 2). [In] The Butterflies and Moths of Northern Ireland