The Common Blue butterfly, scientifically known as Polyommatus icarus, is a widely recognized insect found across a broad native range. It is one of the most familiar butterflies encountered in various open environments.
Identifying Features
The Common Blue butterfly typically measures between 28 and 36 millimeters in wingspan. Sexual dimorphism is evident, with males exhibiting a vibrant, iridescent blue coloration on the upper side of their wings.
Female Common Blue butterflies often display brown or purplish-blue on their upper wings, frequently featuring orange spots along the margins. The underside of the wings in both sexes shares a consistent pattern, characterized by black spots encircled with white rings and additional orange markings near the wing edges.
Life Cycle and Behavior
The Common Blue butterfly undergoes complete metamorphosis, progressing through egg, larva, pupa, and adult stages. Eggs are laid individually on host plant leaves, hatching within one to two weeks. The caterpillar emerges and begins feeding.
Caterpillars primarily feed on legumes such as Common Bird’s-foot Trefoil (Lotus corniculatus) and clover species (Trifolium). This feeding period can last several weeks, during which the caterpillar grows. Caterpillars develop a mutualistic relationship with certain ant species.
Ants are attracted to honeydew, a sugary secretion from glands on the caterpillar’s body. In exchange for this fluid, ants protect caterpillars from predators and parasites. After reaching full size, the caterpillar transforms into a pupa, often at the base of a host plant or in leaf litter, lasting one to three weeks. Adult butterflies emerge, and the species produces two to three broods annually, flying from May to October.
Habitat and Geographic Range
The Common Blue butterfly thrives in a diverse array of open, grassy environments. These preferred habitats include undisturbed meadows, various pastures, and the unique ecosystems of chalk downs. The species is also frequently encountered in more human-modified landscapes, such as gardens, roadside verges, and urban green spaces.
This adaptability contributes to its extensive geographic distribution, which spans across Europe, stretches into North Africa, and extends throughout temperate regions of Asia. The Common Blue butterfly is considered a very common and resilient species. Its ability to inhabit a wide range of environments makes it one of the most frequently observed butterflies across its broad distribution.