The book I used to find these butterflies (British and Irish Butterflies by Adrian Riley) could not have been more accurate. Parking as close to Happy Valley on the Great Orme as I could, I made my way to the upper slopes where the Common Rock-rose was in flower. The scarce Hoary Rock-rose (Helianthemum oelandicum ssp incanum) for which this area is famous flowers earlier and only a few remained with flowers at very top of the limestone cliffs. The Common Rock-rose dominates at this time of year.

Suddenly these beautiful blue butterflies were everywhere. Perhaps they had suddenly hatched in the sudden spell of warm weather but there was a virtual plague of these insects fluttering all round me as I climbed up through the flowers to the cliff tops.

The females vary in colour from quite brownish to those with a bluish hue but the males are fairly consistently metallic blue. The most surprising things is their size - they are quite small butterflies not much larger than Cupido minimus (Small Blue) and smaller than a Common Blue. The male of main sub species (ssp argus) has a black edge to the upper hind wing which is usually continuous but ssp caernensis has intermittent black banding giving a black flecked appearance.

The larval food plants are Helianthemum nummularium (Common Rock-rose) and Lotus corniculatus (Bird's-foot Trefoil) but as I observed these creatures for an hour or so, the adults definitely tended to favour the Rock-rose to settle on.

Slopes above Happy Valley, Great Orme, North Wales 16th June 2010

Added on June 16th 2010, updated 29th May 2011, updated 9th Dec 2014