Holly Blue - Celastrina argiolus

Description

The adults are most easy to identify when at rest, since their pale undersides are distinctive among the blues found in the British Isles, with the possible exception of the Small Blue, which is much scarcer (and, as its name implies, much smaller). The forewings of the female have broad black borders that are absent in the male. However, the adults only tend to open their wings in weak sunshine. Second brood females generally have broader black borders than first brood females. A particular characteristic of this blue is that it will fly high off the ground, distinguishing it from other blues. In this respect they are more similar in behaviour to a hairstreak.

Photo ID?
Habitat

This butterfly is found in many different types of habitat, including gardens, churchyards, woodland, parks and anywhere its food plants and nectar sources can be found.

When to see it

April to early September.

Life History

There are two broods each year, although there may be only one brood in the north. Adults from over-wintering pupae emerge as early as the first week of April in a typical year, with the next generation emerging at the end of July and early August. The main larval foodplants are Holly (Ilex aquifolium) and Ivy (Hedera helix). This species is renowned for fluctuating wildly in numbers, forming a predictable cycle over a few years, believed to be caused by parasitism from the wasp Listrodomus nycthemerus whose sole host is the Holly Blue.

UK Status

This species is found mainly in the south of the British Isles. It is found in England, Wales and Ireland, especially in the south but is largely absent from Scotland.

VC55 Status

Common in Leicestershire and Rutland.

Leicestershire & Rutland Map

UK Map