Holly Blue (Celastrina argiolus) — identification, habitat & look-alikes

Holly Blue is a small blue butterfly native to Europe and much of Asia. In the United States, a similar small blue butterfly is more likely to be a native azure such as Spring Azure (Celastrina ladon); a clear location helps tell them apart.

Appearance

Appearance: The wingspan is about 0.9–1.1 in (22–28 mm). Males are bright blue above, while females have broader dark borders; both sexes are pale beneath with small black spots.

Look-alikes

Spring AzureCelastrina ladon

In most of the eastern United States, a spring-flying azure is more likely Spring Azure. Location and local range are often more useful than a single wing photo because the two can look very similar.

Why they get mixed upSome older classifications treated Spring Azure as part of Celastrina argiolus.

Echo AzureCelastrina echo

In western North America, check Echo Azure first. A clear location is important because a closed-wing photo can closely resemble Holly Blue.

Why they get mixed upBoth are small Celastrina butterflies with pale, black-spotted undersides.

Where it lives

Typical habitats: woodland edges in its native range
parks and gardens in its native range
Range: The Holly Blue is native across Europe and much of Asia. It does not include the North American Spring Azure.

Behavior

Activity: In Britain, adults often fly at head height along hedges and woodland paths near their host plants.
Overwintering: It spends winter as a .

Life cycle

Reproduction: Females place single eggs on flower buds, and the caterpillars feed mainly on buds, flowers, and young fruit.
Caterpillar food plants: In Britain, caterpillars use the flower buds of European holly in spring and ivy later in the year.

Name and classification

About the name: Older North American accounts sometimes included Spring Azure under the name Celastrina argiolus.

Conservation

IUCN Red List: NENot EvaluatedNot yet assessed

Culture and stories

Culture and stories: The English name Holly Blue comes from its spring caterpillars’ use of holly.

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