Field Guide
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Small Blue
Cupido minimus
Not yet photographed by the community
UK's smallest butterfly; dusty blue; chalk and limestone grassland.
Species Profile
Amber List; declining due to habitat loss and fragmentation of grassland reserves
- Lifespan
- 2–4 weeks as an adult butterfly; larvae overwinter and can survive 6–9 months
- Size & Weight
- Wingspan 16–18 mm
- Habitat
- Open, sunny grassland and scrubland with low-growing bird's-foot trefoil, particularly on chalk, limestone, and sandy soils.
- UK Distribution
- Localised to southern England, with populations scattered across the Cotswolds, South Downs, and coastal areas; increasingly rare in the north and absent from Scotland and Wales.
- Diet
- Adults feed on nectar from small wildflowers such as bird's-foot trefoil, clover, and vetches. Caterpillars feed exclusively on bird's-foot trefoil (Lotus corniculatus).
- Predators
- Robins, wrens, and other small insectivorous birds; parasitic wasps and tachinid flies target larvae
- Mating Season
- May to August, with two generations per year in favourable conditions
- Breeding
- Females lay eggs singly on bird's-foot trefoil flower heads. Caterpillars pupate after 3–4 weeks; first generation emerges in June–July, second in August–September. Larvae overwinter in the pupal stage.
- Behaviour
- Males perch on grass stems and low vegetation, darting up to intercept passing females in characteristic skipping flight. Highly sedentary and rarely venture far from their breeding plants. Flight is weak and erratic compared to other blues.
- •The Small Blue is Britain's smallest butterfly species
- •Males have a brilliant blue upperwing while females are predominantly grey-brown with faint blue scaling
- •The caterpillar is attended by ants of the genus Lasius, which feed on sugary secretions from a nectary on the caterpillar's back
- •Population strongholds are rapidly shrinking, making it a conservation priority in several southern English counties
- •Adults are incredibly weak fliers and can be blown off course by even light wind, restricting their range expansion
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