Hertfordshire & Middlesex Branch

Small Blue

Cupido minimus

Very rare and restricted

Distribution and Status

In the two counties, there were concerns that the Small Blue would become extinct in the 1990s but it now appears to be established at several sites including Aldbury Nowers, Hillbrow (west Letchworth), Heartwood Forest, the St. Albans area near the former Butterfly World site and the A41 junction at Bourne End although 2020 and 2021 have seen numbers fall significantly in some places. New colonies were discovered in the Royston area in 2022 and there are possibly other colonies elsewhere where its foodplant, Kidney Vetch grows

Habitat Requirements

Warm and sheltered situations where the larval foodplant Kidney Vetch Anthyllis vulneraria grows on chalk and limestone grasslands, woodland clearings and coastal undercliffs. Quarries, railway embankments and roadside verges can also harbour this butterfly

Larval Foodplants

Kidney Vetch A. vulneraria

Adult Food Sources

Kidney Vetch A. vulneraria, Common Bird's-foot Trefoil Lotus corniculatus, Horseshoe Vetch Hippocrepis comosa

Behaviour/Observation notes

It spends most of its time close to the ground with short flights. Males hold territories on shrubs or grass tussocks often at the bottom of south-facing slopes and mating usually takes place here. After mating, females spend the rest of their lives basking, feeding or laying eggs amongst the foodplants. In dull weather, early morning or late afternoon, the butterflies can be seen roosting about 50cm above the ground on the stems of taller grasses

Life History

There are two generations of this butterfly but the second brood is usually much smaller. It is on the wing in May and early June, and again in August. Eggs are laid on the florets of the foodplant and there may be several on the same flowerhead. The larvae eat the developing seeds until they are ready to pupate on the ground either in mid summer or in the following spring

Further information

Photo gallery
Branch Annual Report (2023)
More on life cycle and status
UK distribution map
Full list of larval hostplants (Lycaenidae)
Account for 2022