Small blue
The Small Blue (Cupido minimus) is a small butterfly species belonging to the family Lycaenidae, recognized as the smallest resident butterfly in the United Kingdom with a wingspan ranging from 16 to 27 mm.[1][2] Males exhibit sooty brown upperwings dusted with silvery blue scales at the base, while females lack this blue and have predominantly brown wings; both sexes feature pale silvery-grey underwings marked with small black dots and a white fringe.[1][3] This Palearctic species is monophagous, with its larvae exclusively feeding on the flowers and seeds of kidney vetch (Anthyllis vulneraria), which serves as both its primary foodplant and oviposition site.[1][2] Native to Europe, Asia Minor, and parts of Siberia, the Small Blue has a widespread but patchy distribution across the Palearctic region, extending from northern Spain and Greece northward to Scandinavia and eastward to the Russian Far East.[4] In the British Isles, it is most abundant in south-central England, particularly on chalk and limestone grasslands, with scattered colonies along the eastern Scottish coasts, south Wales, and the east and west coasts of Ireland.[2][1] Preferred habitats include sheltered, warm calcareous grasslands, coastal dunes, undercliffs, quarries, road embankments, and other early successional sites where kidney vetch thrives, often in areas with light grazing to maintain short vegetation.[2][3] The butterfly's life cycle is annual and single-brooded in most regions, though a partial second brood occurs in some southern UK populations in warm years, with adults emerging from mid-May to early July in southern populations and slightly later northward.[1] Females lay eggs singly on the flowerheads of kidney vetch between mid-May and late June, and the resulting caterpillars, which are cannibalistic, feed on the anthers and developing seeds before overwintering as larvae in diapause from late summer. Pupation occurs from mid-April onwards.[1][3][5] Adults, which can live up to three months, nectar on flowers such as common bird's-foot-trefoil (Lotus corniculatus) and horseshoe vetch (Hippocrepis comosa), with males often perching territorially on low vegetation to attract mates.[3][1] Conservation efforts for the Small Blue are prioritized due to its vulnerability, with populations in Great Britain classified as Near Threatened on the 2022 UK Red List and showing a 43-44% decline in distribution since the 1980s, although 2025 records indicate significant increases in some Scottish sites, attributed to habitat loss from agricultural intensification, scrub encroachment, and coastal development.[2][1][6] It is protected under the UK Wildlife and Countryside Act 1981 and designated as a priority species in the UK Post-2010 Biodiversity Framework, with management focusing on maintaining kidney vetch-rich grasslands through controlled grazing and habitat restoration.[3][1]Taxonomy
Scientific classification
The Small blue, scientifically known as Cupido minimus (Fuessly, 1775), belongs to the order Lepidoptera within the class Insecta.[7][8]| Taxonomic Rank | Name |
|---|---|
| Kingdom | Animalia[7] |
| Phylum | Arthropoda[7] |
| Class | Insecta[7] |
| Order | Lepidoptera[7] |
| Family | Lycaenidae[7] |
| Subfamily | Polyommatinae[8] |
| Genus | Cupido[7] |
| Species | Cupido minimus[8] |