What is "holly blue"

n. A blue butterfly, (taxlink Celastrina argiolus species noshow=1), of the family Lycaenidae.

The holly blue (Celastrina argiolus) is a butterfly that belongs to the Lycaenids or blues family and is native to Eurasia and North America.

The holly blue has pale silver-blue wings spotted with pale ivory dots. In Europe, the first generation feeds mainly on holly (Ilex aquifolium) but the second generation uses a range of foodplants.