From Gwen Norman
Come mid June, I always go to a sunny spot on the limestone escarpment of Lansdown, near Bath, just off the Cotswold Way, to see the Small Blue in its habitat. This butterfly breeds on the Kidney Vetch Anthyllis vulneraria and locally this is the only spot I know where this flower blooms.
The Small Blue is so called because of its dusty dark blue colour and pale underwing with dark spots. The female has a light edge on the topside. It is the smallest butterfly in the British Isles.
The mature female butterfly, after mating in late spring, lays its eggs into the flower heads of the Kidney Vetch. The resultant caterpillars eat and burrow their way into the flower head and at the same time show cannibalistic tendencies so that finally only one caterpillar is left in each flower head. These survivors go into hibernation as early as July after gorging themselves on the embryo seedpods. After spinning together a few flower heads they remain there throughout the winter months. At the beginning of May, the caterpillars leave their winter retreats, spin pads of silk and bind themselves upright onto the stem of surrounding plants where they eventually change into chrysalides. The Small Blue butterfly emerges after a couple of weeks ready for the mating season. The butterfly is on the wing until mid summer. Year after year the Small Blues will live and breed in the same place.
The Kidney Vetch is found in dips and hollows on chalk and limestone grasslands. The flowers are a rich source of nectar, but only certain insects, such as the bumblebees are able to open the stiff, large petals. The flower colour varies from yellow, orange, red, purple, to off-white. The sepals are purple tipped and woolly, enclosing the pod.
In the Middle Ages, the plant was used for speeding the healing of wounds, hence its Latin name 'vulneraria'. There are several local names, such as; Butterfingers, Fingers and Thumbs, Double Pincushion and Lamb's Foot.
Due to the Small Blue's specific habitat, it is a rare pleasure to see this delightful small blue butterfly flitting amongst the green grasses and the bright summer flowers.