Common blue butterfly

  • Scientific name: Polyommatus icarus
  • Type: Insects

Key information

Male common blues have violet-blue upper wings with grey-beige undersides. However, females vary from those with predominantly brown upper wings and orange crescents, usually more common in the south, to those with more blue, found farther north and west.

This butterfly is common throughout the UK. There are often two broods, with eggs laid in June, then August and September. Common blue caterpillars hibernate and pupate in April and May giving rise to adults in May and June.

The caterpillars are short, green and furry. They feed on the underside of young leaves, leaving the upper leaf epidermis intact. This creates silvery blotches on the leaves that are easy to spot.

The caterpillars secrete nutrient-containing substances that attract ants. In turn, the ants protect the caterpillar from predators. Ants probably tend the chrysalis too.

What they eat:

Adults drink nectar from flat-headed flowers. Caterpillars eat wild, leguminous plants such as bird's-foot trefoil, rest harrow and white clover.



Identifying features:

Natural habitats: Flower border Herb garden Meadow area Shrub Woodland area

Where and when to see them

Feeding on a variety of flat-headed flowers, basking in the sunshine. Caterpillars on young, leguminous plants such as white clover. Also in grassland, grassy dunes, meadows, woodland clearings, heaths.

Adults between May and September, sometimes October in warm years. Caterpillars are present throughout the year except May and late July-early August.

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