Small Blue Cupido minimus (Fuessly 1775 )
Family: Lycaenidae, subgroup Polyommatinae (The Blues)
Iain H Leach
Iain H Leach
The Small Blue is a very small, easily overlooked butterfly with dusky purple-blue upperwings, and pale grey-blue underwings with black dots (similar to the Holly Blue). It can also look quite brown.
The male has a dusting of blue scales towards the centre of the upperwings. Both sexes show weak, fluttery flight and it can be confused with the Chimney Sweeper moth Odezia atrata. ln flight, it might also be confused with the Brown Argus, although at rest, the latter's orange lunules (on the upperwings), and the more colourful patterned underwings, are distinctive.
This butterfly needs dry, sheltered grasslands with Kidney Vetch Anthyllis vulneraria which is its only known caterpillar foodplant. Typically, this habitat is often found on chalk and limestone, although it can also be found in quarries, along road and railway embankments, and on cliff tops and coastal dunes. Kidney vetch is a colonising plant and needs a continuing element of erosion, or wear and tear, on the habitat, to help maintain its presence. The butterfly can manage to survive in extremely small areas because it doesn’t move far during its life and therefore it’s easy for colonies to be overlooked.
The Small Blue has a range from northern Spain across Europe and Asia. In Britain it survives along the coasts of eastern Scotland, the south of England and the south of Wales. In Yorkshire it is only still present on one site.
The species is normally single brooded from mid-May to late June, but a partial second generation is possible in southern England from late July to August in good years.
Eggs are usually laid singly on kidney vetch flower heads and where two or more larvae end up on the same plant, the strongest is likely to fight and eat any weaker ones. Larvae hibernate through winter hidden in the soil surface and they can stay in diapause (a state of inactivity) for 15 months. Pupation takes place from April to May.
Adults are often very sedentary, rarely moving more than about 40 metres in a lifetime, although occasional longer movements to new sites have been seen. Colonies are usually very small with less than around 30 butterflies.
Larva on Kidney Vetch Flower: Nick Hall
Butterfly Conservation priority: Medium
Section 41 species of principal importance under the NERC Act in England
Section 42 species of principal importance under the NERC Act in Wales
Northern Ireland Priority Species
UK BAP status: Priority species
Protected under Schedule 5 of the 1981 Wildlife and Countryside Act (for sale only)
Fully protected under the 1985 Northern Ireland Wildlife Order
With thanks to the Butterflies of Yorkshire edited by Howard M Frost
Catherine Jones 10/11/2020