Common blue (Polyommatus icarus)

The Common Blue (Polyommatus icarus) is a small, widespread butterfly belonging to the family Lycaenidae. It is one of the most common and easily recognizable blue butterflies in Europe. Here’s an overview of the Common Blue:


  • Size: The wingspan ranges from 28 to 36 millimeters.
  • Coloration:
  • Males: The upper sides of the wings are a bright blue with a thin black border and a white fringe.
  • Females: The upper sides are brown with a variable amount of blue near the body and a series of orange spots along the edge of the wings.
  • Undersides: Both sexes have greyish-brown undersides with numerous small black spots circled in white and a series of orange spots along the margins of the hindwings.


  • Preferred Habitats: The Common Blue thrives in a variety of habitats, including grasslands, meadows, gardens, roadsides, and coastal dunes. It prefers areas with an abundance of leguminous plants, which serve as host plants for its larvae.
  • Geographic Range: The species is found throughout Europe, North Africa, and temperate Asia. It is widespread and often abundant in suitable habitats.


  • Feeding: Adults feed on nectar from various flowering plants, including clover, buttercups, and knapweed. The larvae feed on the leaves and flowers of leguminous plants, particularly common bird’s-foot-trefoil (Lotus corniculatus) and other trefoils.
  • Activity: They are diurnal and most active during warm, sunny days. Males can often be seen patrolling low over the ground in search of females.
  • Flight: The flight period extends from April to October, depending on the climate and location. There are usually two or three generations per year.

Life Cycle:

  • Eggs: Females lay eggs singly on the leaves and flower buds of host plants.
  • Larvae: The caterpillars are green with a dark dorsal stripe and are well-camouflaged against the host plant. They are often tended by ants, which provide protection in exchange for sweet secretions from the larvae.
  • Pupae: Pupation occurs on the ground or among the vegetation. The pupae are brown and blend in with their surroundings.
  • Adults: Adults emerge after a few weeks of pupation and are ready to mate and continue the life cycle.

Ecological Role:

  • Pollination: As nectar feeders, adult Common Blues contribute to the pollination of a variety of wildflowers.
  • Ant Mutualism: The larvae’s relationship with ants is a notable aspect of their ecology, benefiting both the butterflies and the ants.
  • Food Web: Both larvae and adults are important prey for various predators, including birds, spiders, and other insects.

Conservation Status:

  • Population: The Common Blue is currently not considered threatened and is one of the most widespread and abundant butterflies in its range.
  • Threats: Habitat loss, agricultural intensification, and the use of pesticides can locally impact populations. Conservation efforts focus on preserving and restoring suitable habitats.

Interesting Facts:

  • Color Variations: The extent of blue on the upper sides of the female’s wings can vary significantly between individuals and populations.
  • Ant Associations: The mutualistic relationship between the larvae and ants is fascinating and enhances the larvae’s survival.
  • Adaptability: The Common Blue’s ability to thrive in a wide range of habitats contributes to its widespread distribution and success.

Identification Tips:

  • Blue Males: Look for the bright blue upper wings of males, especially in sunny, grassy areas.
  • Underside Patterns: The greyish-brown undersides with black and orange spots are distinctive and help in identifying both sexes.
  • Habitat Preference: Observing them in a variety of habitats, including grasslands and gardens, can aid in accurate identification.

In summary, the Common Blue (Polyommatus icarus) is a charming and widespread butterfly with distinctive blue and brown coloration, interesting ecological interactions with ants, and a presence in diverse habitats. Its adaptability and abundance make it a familiar and beloved species among butterfly enthusiasts and conservationists alike.

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