Common Blue

The Common Blue (Polyommatus icarus) is the UK's most widespread blue butterfly, featuring brilliant blue males and brown females with orange-spotted margins. These small insects (35mm wingspan) hibernate as caterpillars, rely on legumes like bird's-foot trefoil, and can be found in gardens, grasslands, and sand dunes.

Key Facts About the Common Blue Butterfly:

• Gender Differences (Sexual Dimorphism): Males are a brilliant, iridescent blue, while females are usually brown with a dusting of blue near the body, though some (especially in Scotland and Ireland) can be quite blue. Both have distinctive orange spots on the undersides of their wings.

• Unique Hibernation: These butterflies spend the winter as caterpillars. In autumn, the caterpillars crawl down their foodplant and hide under leaves, in moss, or within leaf litter for up to six months before emerging in March.

• Multiple Generations: The species is usually double-brooded, with generations flying from May to September, but in warm years, a third brood can emerge.

• Habitat Variety: They are highly adaptable, found in diverse, sunny habitats such as coastal cliffs, sand dunes, woodland clearings, and even suburban gardens.

• Diet and Life Cycle: The caterpillars feed primarily on legumes, including Common Bird's-foot Trefoil, Black Medick, and White Clover.

• "Common" yet Distinct: Although common, they are distinguished from other blues by their vibrant color and lack of a black-and-white checkered fringe on their wings.

• Dispersal: While not migratory, they can undertake partial migrations, searching for new, suitable habitats.