Mating of the Common Blue Butterfly

Female (left) and male (right) Common Blue butterfly (Polyommatus icarus), mating

The Common Blue butterfly (Polyommatus icarus) generally produces two broods per year in Ireland, May/June and August/September. However this may vary depending on the part of the island. In the north there is evidence for only a partial second brood, whereas on the south coast there are at least three broods, being centered around April, July and September (1). P. icarus favours rough, dry grassy areas, sand dunes and roadside verges where its preferred larval food, Bird's Foot Trefoil (Lotus corniculatus) grows. Adults will also feed on this plant and females have been shown to lay eggs on plants with flowers in preference over those without (2). The mating pair pictured were observed in a patch of rough ground dominated by Kidney Vetch (Anthyllis vulneraria), Thrift (Armeria maritima), Red Clover (Trifolium pratense) and Bird's Foot Trefoil in a coastal area. P. icarus has an almost Palaeartic distribution and a sub-species, P. icarus mariscolore exists in Ireland that is slightly larger and more brightly coloured than the sub-species P. icarus icarus found in Britain (1).

Male Common Blue butterfly, Polyommatus icarus

References:

1. Nash et al., 2012. Ireland's Butterflies A Review pp. 156-158
2. Janz et al., 2005. OIKOS 109 pp. 535-538