Celastrina

Celastrina is a genus of small butterflies in the family Lycaenidae, commonly known as azures because males typically display pale blue uppersides. Females are often brown or gray with blue accents, and the underside of both sexes is pale with a pattern of small dark markings and a row of small marginal spots.

Distribution and habitat include temperate regions across Europe, Asia, and North America. Members of the genus inhabit open woodlands, hedgerows, clearings, and edges of fields and streams. They favor sunny, sheltered microhabitats with abundant nectar sources, such as dandelion, clover, and other small flowers.

Ecology and life history feature eggs laid on host plants, often on flower buds or new growth. The larvae feed on flowers and developing shoots of various shrubs and trees. Many Celastrina species engage in mutualistic relationships with ants during larval stages, a common trait among Lycaenidae. Some species overwinter in the egg or larval stage, while others survive as pupae, with adults typically emerging in spring or early summer. The flight period is usually short and can be two generations per year in mild climates, or a single generation in cooler regions.

Taxonomy and diversity note that the genus contains about a dozen described species, with regional variations in species boundaries. Notable members include Celastrina ladon, commonly called the spring azure in North America, and Celastrina argiolus, known as the holly blue in parts of Europe and Asia. Identification often relies on the patterning and coloration of the underside, as well as geographical range and seasonal timing.