Holly Blue (Celastrina argious)

.... and in Manx that's Gorrymag hollin

Passport crop

This is one of only two species of blue found on the Island but their habitats are vastly different.

The Holly Blue is a butterfly of woodland or shrubby areas where its foodplants grow in sheltered sunny positions. It is the only British butterfly to use different foodplants according to the time of year. The spring brood emerges in late April and the spring foodplant is Holly. The eggs are laid singly on female flowers and the caterpillar feeds on the developing berries. The second brood eggs are laid in late summer on Ivy flowers and again the caterpillars feed on the developing berries.
The upper wings are bright blue and the female has distinctive black borders. The black borders are larger in the second brood. The underwings are blue with small black spots. Double brooded although on the Island the second brood may only be partial. On thw wing from early March to June and again from late July through August. Overwinters as a pupa.

Aside from the generally different habitats in which they are found, a fairly reliable way of telling Common Blue from Holly Blue is that if you have to look up to see a blue butterfly then it is likely to be a Holly Blue.