Here’s a detailed natural history overview of the Common Blue (Polyommatus icarus), one of Europe’s most widespread and recognizable butterflies:

**Common Blue (Polyommatus icarus)**

Taxonomy & Classification

Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Lepidoptera
Family: Lycaenidae (blues, coppers, hairstreaks)
Genus: Polyommatus
Species: P. icarus

General Description

A small but striking butterfly, often abundant in grasslands and meadows.

Wingspan: 28–36 mm.
Male: Brilliant violet-blue upperside with a thin black margin and white fringe.
Female: Variable—usually brown with orange spots along the edges, sometimes with a blue suffusion, especially in southern populations.
Underside (both sexes): Greyish-brown with a series of black spots, orange lunules, and metallic blue scales near the wing base.
Sexual Dimorphism: Very marked, with males and females differing strongly in coloration.

Behavior & Lifestyle

Flight Period:
- April to October, in 2–3 broods depending on climate (more in southern Europe).
Flight: Low, fluttering but rapid, often close to vegetation.
Feeding:
- Adults nectar on a wide range of flowers, especially clovers, bird’s-foot trefoil, knapweeds, scabious, and thistles.
Mating Behavior:
- Males actively patrol territories in search of females.
- Females are more secretive, spending more time near host plants.

Life Cycle

Eggs: Tiny, white, laid singly on host plants.
Caterpillar: Small, green with faint stripes, slightly flattened—cryptic among plant material.
Larval Food Plants: Various legumes (Fabaceae), particularly:
- Bird’s-foot trefoil (Lotus corniculatus)
- Common restharrow (Ononis repens)
- Clover (Trifolium)
- Medick (Medicago)
Overwintering Stage: Usually as a small larva, hidden at the base of plants.
Pupation: Occurs in a loose cocoon on or near the ground.

Habitat

Prefers open, sunny habitats:
- Grasslands, meadows, heaths, road verges, field edges, dunes, and wasteland.
Avoids dense woodland and heavily shaded areas.

Geographic Range

Europe: Very widespread, from the Iberian Peninsula to Scandinavia and across Eastern Europe.
Asia: Extends through temperate Asia into Siberia, Central Asia, and parts of the Middle East.
North Africa: Present in Morocco and nearby regions.
British Isles: One of the commonest blue butterflies, found almost everywhere except the far north of Scotland.

Ecological Role

Pollinator: Important nectar visitor for wildflowers.
Larval Interactions: Caterpillars often tended by ants (myrmecophily), which offer protection in exchange for sugary secretions.
Food Source: Adults and larvae are prey for birds, spiders, and predatory insects.

Special Adaptations

Sexual Dimorphism: Helps reduce competition between sexes, with different camouflage strategies.
Ant Associations: Caterpillar-ant mutualism increases larval survival.
Wide Host Range: Ability to use many legumes allows it to colonize diverse habitats.

Conservation Status

IUCN Red List: Least Concern
Population Trend: Stable and often abundant.
Threats:
- Loss of wildflower-rich grasslands due to intensive agriculture.
- Pesticide use and urbanization.
Conservation Needs: Maintenance of flower-rich meadows and field margins.

Interesting Facts

Despite its name, the female Common Blue is not blue at all in many regions—adding to confusion with other “brown” butterflies.
Often the most numerous blue butterfly seen in Europe.
The species name icarus refers to Icarus of Greek mythology, who flew too close to the sun.
Frequently used as an indicator species for the health of grassland ecosystems.