Common Blue
Polyommatus icarus
The Common Blue is one of the most widespread butterflies in Europe and temperate Asia. It inhabits a wide range of open habitats, including nutrient-poor grasslands, meadows, and even gardens. The species exhibits strong sexual dimorphism, with males featuring vibrant blue wing uppersides. The larvae feed on various legumes, particularly bird's-foot trefoil and restharrow.
Details
Identification
Undersides of wings grey-brown with black, white-ringed eye spots and orange marginal spots; basal spot present on the underside of the forewing.
Social behavior
Solitary; males exhibit territorial behavior when searching for females.
Diet
Larvae feed on the leaves of legumes (Fabaceae); adults consume nectar from a wide variety of flowering plants.
Spawning substrate
Leaves and stems of Fabaceae, especially Lotus corniculatus and Ononis species.
Overwintering
Overwinters as a larva (L3 instar) in the leaf litter or at the base of the host plant.
Ecology
Ecological role
Pollinator and important food source for insectivorous birds and invertebrates.
Natural predators
Birds, spiders, predatory bugs, ichneumon wasps (parasitoids).
Competitor species
Other lycaenid species such as the Chalk Hill Blue (Polyommatus coridon) in overlapping habitats.
Ecosystem service
Pollination of wild plants and promotion of biodiversity.
Threats
Agricultural intensification, eutrophication, loss of fallow land, and pesticide use.
Scientific profile
Profile
Distinguishing features
Characteristic is the basal spot in the cell on the underside of the forewings (absent in Polyommatus thersites). On the hindwing underside, there is often a white, wedge-shaped streak between the orange submarginal spots and the postdiscal region. The fringes are pure white and not checkered (distinction from P. bellargus).
Habitat
Highly euryoecious species; inhabits a wide range of open land habitats such as nutrient-poor grasslands, meadows, fallow land, embankments, forest edges, as well as gardens and parks in urban areas.
Protection & threats
Main threats
Agricultural intensification (frequent mowing, high fertilizer input), loss of fallow land and nutrient-poor grasslands, habitat fragmentation, and increasing land sealing.
Population trend
Overall stable and widespread in Germany, though local declines are recorded in intensively used agricultural landscapes (Red List Germany: Least Concern).
Conservation measures
Promotion of extensive grassland management, preservation of margin structures, reduction of pesticide use, and creation of stepping-stone biotopes to link populations.