Wingspan: 26–35 mm
Flight period: in two or three generations from mid-March to November
Larval food plants: herbs and shrubs from families Rhamnaceae, Fabaceae, Cornaceae, Rosaceae and Ranunculaceae
The holly blue (Celastrina argiolus) belongs to our larger blues. During resting, nectar sipping, or drinking water with dissolved minerals from moist soil, it can be identified by its distinctly light, bluish-white-gray underside of the wings, which is decorated with a pattern of small black spots and specks. The upperside of the wings in males is sky blue, and the edge is accentuated by a thin black band only at the outer corner of the wings.
The base color of the upperside of the female's wings is somewhat darker blue; it clearly differs from the male by a broad black band that starts in the upper corner and continues along the entire outer edge of her forewings. The dark markings on the upperside of the hindwings in the female are limited to the upper corner of the wing, along the outer edge of the wings there are five or six small black dots arranged in a row.
The holly blue is one of the most adaptable and widespread species of butterflies in our country. With the exception of high mountains, it can be observed practically everywhere where there are forest edges, shrubs or hedgerows. Most often you will see it flying along the forest edge or perched in shrubs; it is common on dry, damp and cultivated meadows, but you may also encounter it along forest paths, in parks or in gardens. It prefers to stay in lowlands, and it has also been observed up to 1300 m above sea level.
