Holly Blue (Celastrina argiolus)
The Holly Blue is a common garden visitor and is also seen in parks, churchyards, hedgerows and woodland rides. It is widespread in England and Wales but is rarer in Ireland. It undergoes large fluctuations in numbers from year to year. It has expanded northwards in recent years and has colonised parts of midland and northern England.
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 range of other wild and garden plants including Spindle (Euonymus europaeus), dogwoods (Cornus spp.), snowberries (Symphoricarpos spp), gorses (Ulex spp.), and Bramble (Rubus fruticosus).
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).
Wings are bright blue and have a span range (both male and female) of 35mm. Females have black wing edges. Undersides pale blue with small black spots which distinguish them from the Common Blue.