Holly Blue

• Latin name: Celastrina argiolus
• Family group: Blues
• Countries: England, Scotland, Wales, Ireland
• Size: Small

Resident

Range expanding in Britain.

The Holly Blue is easily identified in early spring, as it emerges well before other blue butterflies. It tends to fly high around bushes and trees, whereas other grassland blues usually stay near ground level. It is much the commonest blue found in parks and gardens where it congregates around Holly (in spring) and Ivy (in late summer).

The Holly Blue is widespread, but undergoes large fluctuations in numbers from year to year. It has expanded northwards in recent years and has colonized parts of midland and northern England.

Conservation status

• UK Biodiversity Action Pal: not listed
• Butterfly Conservation priority: low
• European threat status: not threatened
• Protected in Northern Ireland

European/world range

Widespread in Europe between 40B:N and 67B:N and as far east as Japan, as well as being found in North Africa and North America. Its European range is stable, although there have been recent expansions in a few European countries.

Foodplants

The larvae feed predominantly on the flower buds, berries, and terminal leaves of Holly (Ilex aquifolium) in the spring generation, and Ivy (Hedera helix) in the summer generation. The spring generation can complete larval development entirely on leaves of male Holly bushes, although female bushes are preferred. They also use a wide variety of other wild and garden plants including Spindle (Euonymus europaeus), dogwoods (Cornus spp.), snowberries (Symphoricarpos spp.), gorses (Ulex spp.), and Bramble (Rubus fruticosus).

Habitat

The Holly Blue occurs in a wide range of habitats, including hedgerows, field margins, woodland rides, gardens, and parks, including those in urban and suburban areas. In England, it often breeds in churchyards, many of which have Holly and Ivy. In Ireland, it is limited mainly to deciduous woods with Holly and, occasionally, country gardens.