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Small Blue (Cupido minimus)

On this page, we have made available all the information we have for this species

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Picture of Small Blue
© Nick Greatorex-Davies

The Small Blue is a small, very localised and easily overlooked butterfly that occurs in small discrete colonies on herb-rich grassland on calcareous soils where its foodplant Kidney Vetch (Anthyllis vulneraria) grows. It has declined throughout most of its British range. Changes in management are likely to affect the quantity and quality of foodplant available for oviposition and subsequent survival of the larvae. Some disturbance is usually necessary to provide good germination sites for the establishment of new plants of this biennial or short-lived perennial.(For further details on this species see

Family : Lycaenidae

Status : Stable

Status details :
Status since 1978 is Stable with a decrease of -18.3%
Status over the last 20 years is Stable with a decrease of -3.5%
Status over the last 10 years is Stable with a decrease of -17.5%

Log collated index plot

Species Log Collated Index Plot

This chart shows the index of abundance (LCI = Log Collated Index) over time. It shows fluctuations in populations from year to year, and is scaled so that the average index over the whole series is equal to 2 (horizontal line). For greater detail about how this index is derived, click on the green question mark above.

Trend description :
This butterfly is recorded regularly on a relatively small number of transects and the data show no significant trend. This is reflected in the site level trends, with no significant declines or increases at any site with sufficient data to calulate a long-term trend. Abundance on monitored sites can be extremely large, reaching three figure indices regularly at sites such as Swyncombe Downs in Oxfordshire, where in 2005 Small Blue produced an impressive site index of 1,042, the highest recorded on any UKBMS site. It was once considered a normally single-brooded species in Britain and Ireland, but in recent years it has shown an increasing tendency to produce a second brood, presumably in response to a warming of the climate.

This map shows the distribution between 1995 and 2016. Data is derived from the Butterflies for the New Millenium dataset via the NBN Gateway

Phenology plot
Species Phenology Plot

Phenology plot

This chart shows the average number of butterflies seen on transects between Arpil and October across all sites (fitted values from a Generalised Additive Model). The blue line gives average counts over the full BMS series (1976 to date) and the red line gives the average for the last year.

Species abundance map


This map shows symbols for the mean abundance at transect sites, with the colour of the symbol reflecting the level of abundance. Means are over all years. Grey background squares are the occupied cells as shown by the Butterflies for the New Millenium over the previous ten year period.


In total, Small Blue has been recorded from 282 transects in the Butterfly Monitoring Scheme. Of these, annual indices of abundance have been calculated from 257 sites, with an average index of 15 individuals per site.

For 84 of these sites, Small Blue has been recorded well enough to calculate annual indices of abundance in more years, allowing trends to be calculated.

In 2019, 2714 individuals were recorded from 83 sites, producing annual indices at 69 of these.

The UK Butterfly Monitoring Scheme is organized and funded by Butterfly Conservation (BC), the UK Centre for Ecology and Hydrology (CEH), the British Trust for Ornithology (BTO), and the Joint Nature Conservation Committee (JNCC). The UKBMS is indebted to all volunteers who contribute data to the scheme.