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.