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Small Blue butterfly (Cupido minimus)

Small blue, Small blue


The small blue butterfly is one of the smallest butterflies found in the UK, with a wingspan of just 20-30mm they are often hard to spot!  You can see them flying in late May to June, and in good years a second brood can emerge in August. They are happiest in sunny and sheltered areas, typically on open stony or sandy limestone that supports finer grasses and wildflowers. An abundance of kidney vetch is essential, as it is the only plant that the females use to lay their eggs. The larvae live and feed on the flower heads during summer months, dropping to the ground and nestling in the soil to become dormant over winter, before entering chrysalis phase in late April and emerging as adults in spring.  


This butterfly has a wide geographic range and is found from northern Scotland to the south of England, with colonies also in Wales and Ireland. However, outside of its strongholds in the south of England, colonies are often isolated and left vulnerable to extinction. The small blue is now absent from the western and northern Scottish isles, the Isle of Man and the Channel Islands. In Cumbria, the species occurs on three sites, typically near the coast on abandoned industrial locations, such as the slag banks in Barrow in Furness and brownfield sites near the coastal towns of Maryport and Whitehaven. Despite conservation efforts and translocations the small blue has suffered a 44% population decline since the 1970s.   

Reason for decline 

The UK population of the small blue butterfly has declined as a result of extensive land use change, overgrazing of grassland, and the general spread of scrub on grassland and brownfield sites. The small blue butterfly tend to thrive in post-industrial areas such as disused railways and slag heaps. However, these sites are almost always first on the list for development, meaning that populations are constantly at threat of being destroyed. 

Project aims 

The aim of the small blue project is to expand the current population and extend the geographic range of the species, working with Butterfly Conservation, landowners and local communities. As a team we will improve the habitat at known small blue sites and also in connected areas where they are likely to thrive. Once we are certain that the population is stable and self-sufficient, we will initiate an exciting adult translocation program in the final year of the project.

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