Vulnerable butterfly in the Botanical Garden

The Small Blue, Cupido minimus, is a small brown butterfly with a wingspan of 18–25 mm. The underside of its forewing features a band of small black dots surrounded by a white ring.

It is the smallest of around 20 species of blue butterflies in Sweden and inhabits sunny, preferably calcium-rich, hay meadows. As the number of hay meadows in Sweden has fallen by 80 percent since the 1930s, this little brown butterfly is now found primarily on shingle beaches, in abandoned gravel pits and on warm roadside embankments where Kidney Vetch plants thrive.

The Small Blue is very loyal to its local habitat and is often found in large numbers in small areas. As these areas are declining sharply, the Small Blue is classified as a vulnerable species on the Swedish Red List

Dependent on Kidney Vetch

Kidney Vetch, Anthyllis vulneraria is a legume that thrives on open, dry, sandy or gravelly ground. The female Small Blue lays her eggs in the flowers of the Kidney Vetch. Once the eggs have hatched, ants care for the butterfly’s caterpillars.

The Small Blue is therefore found primarily where Kidney Vetch grows, but the female may also lay her eggs on Bird’s-Foot Trefoil and various species of Milkvetch (Astragalus).

Small Blue in the Botanical Garden

The Small Blue is abundant in one of the meadows in the Botanical Gardens, where the grass is mown in mid-July or later. It is a habitat with plenty of nectar, and around 20 butterflies can be seen flying low over the grass on sunny days.

There is no Kidney Vetch available as food for the caterpillars in this meadow, but there is Bird’s-Foot Trefoil and other legumes (Red Clover, Bush Vetch, Black Medic and Meadow Vetchling). The Ödeenska meadow is also located nearby, which is home to a few stands of Kidney Vetch.

Given the butterfly’s dependence on Kidney Vetch, its future in the meadows of the Botanical Garden remains uncertain.

Anders Backlund, Garden Director of the Botanical Garden, on the discovery in the Botanical Garden:

“We are, of course, delighted that this Red Listed butterfly has found its way to our meadow in particular. It shows that our work to promote biodiversity is paying off. Let’s hope that we will see the Small Blue flying around here again next year, and that our meadows continue to attract a variety of other species in the future!"