Small Blue

Cupido minimus (kew-PY-doh MI-nim-uss)

Small Blue (m) Totternhoe Quarry, Beds; 2nd June 2010
Photo © millerd

18 - 27mm

Checklist Number

Family:LycaenidaeLeach, 1815
Subfamily:PolyommatinaeSwainson, 1827
Tribe:PolyommatiniSwainson, 1827
Genus:CupidoSchrank, 1801
Subgenus:CupidoSchrank, 1801
Species:minimus(Fuessly, 1775)

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This is our smallest resident butterfly with a wing span that can be a little as 16mm. The sexes are similar in appearance, although the male upperside is almost black with a dusting of blue scales, whereas the female is more dark brown in colour. Both sexes have an underside that is silvery-grey in colour, and not unlike that of the Holly Blue. This butterfly has a large distribition, being 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 pockets, typically in coastal locations. Most colonies consist of less than 30 adults, although a few colonies consist of thousands of adults. This butterfly is absent from the western and northern Scottish isles, the Isle of Man and the Channel Islands.

Cupido minimus

This species was first defined in Fuessly (1775) as shown here (type locality: Switzerland).

Small Blue - Bishops Hill, Warwickshire 17.05.2014

Photo © Neil Freeman

Small Blue, Male, MHD, 28/07/2014

Male Underside
Photo © Pauline

Small Blue, female, Kithurst Hill, West Sussex, 9 June 2012

Photo © Colin Knight

Small Blue - imago - Martin Down - 31-May-06 (0195)

Female Underside
Photo © Pete Eeles

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Conservation Status

The population trend of this dainty butterfly is considered relatively stable, whereas the distribution trend shows a distinct decline, with the butterfly completely disappearing from some areas. For example, this species is now considered extinct in Northern Ireland with the last sighting in 2001. This species is therefore considered a priority species for conservation efforts.

UK BAP StatusDistribution Trend (%)Population Trend (%)
Priority Species
Click here to access the Biodiversity Action Plan (BAP) for this species.

The table above shows the distribution and population trends of species regularly found in the British Isles. The distribution trend represents a comparison between data for the periods 1995-1999 and 2005-2009. The information provided is taken from the Butterfly Conservation report The State of the UK's Butterflies 2011. The UK BAP status is taken from the UK Biodiversity Action Plan (UK BAP) (2007 review).


Suitable sites for this species are those that are sheltered and contain a good amount of Kidney Vetch, together with grasses and shrubs which are used for perching and roosting. A wide variety of habitats is used, including unimproved chalk and limestone grassland, abandoned quarries, road and railway embankments and woodland rides and clearings.



Click here to see the distribution of this species or here to see the distribution of this species together with specific site information overlaid.

Life Cycle

Adults generally appear in early May in southern sites, reaching a peak at the end of May and start of June. This butterfly has a partial second generation each year, except in northern Scotland.

The chart(s) above have been correlated with the phenology plot below, taken from the UK Butterfly Monitoring Scheme. The blue line gives average counts over the full data set from 1976 to date, and the red line gives the average for the last year.


Both sexes spend a large amount of time basking or resting. Males perch on small shrubs or grass stems which they leave when investigating passing insects or when searching out nectar sources. They are not territorial, however, and can often be found in small groups of 2 or 3. Both sexes take nectar from various flowers, with Kidney Vetch, Bird's-foot Trefoil and Horseshoe Vetch being particular favourites. Males will also take salts and minerals from damp mud, animal droppings and carrion.

Virgin females entering the perching sites are quickly mated without any elaborate courtship. Once mated, the female spends most of her time searching out suitable plants on which to lay and, once found, she lays a single egg between 2 florets on the flower head. She then rubs her abdomen over the flower head which is believed to deter other females from laying on the same plant since the larvae are cannibalistic in their first instar.

Adults feed primarily on Bird's-foot Trefoil (Lotus corniculatus), Kidney Vetch (Anthyllis vulneraria) and Vetches (Vicia spp.).

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Several eggs are occasionally found on the same inflorescence, although these will generally have been laid by different females. The eggs are quite easy to find at suitable sites, and hatch in 1 to 3 weeks depending on temperature.

Small Blue ovum - Found at Durdle Door, Dorset - 16.06.14

Photo © Tony Moore

Small Blue - ovum - Magdalen Hill Down - 11-Jun-15-8

Photo © Pete Eeles

Small Blue - ovum - Magdalen Hill Down - 26-Jun-12-1

Photo © Pete Eeles

Small Blue ovum, Magdalen Hill Down, 27/05/2015

Photo © Pauline

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The newly-hatched larva is less than 1mm in length and immediately burrows into a floret where it feeds on the developing seed. As the larvae grow they start to feed outside the floret with their head buried deep inside, with their back end exposed. The larva hibernates on the ground, often under moss or in a crevice in the soil. The larvae emerge in the spring and, without feeding further, wander off to find a suitable pupation site. There are 3 moults in total.

The primary larval foodplant is Kidney Vetch (Anthyllis vulneraria).

Small Blue larva, Magdalen Hill Down, 22/07/2015

Photo © Pauline

Small Blue larva - Caterham, Surrey 2-Aug-2012 L1

Photo © Vince Massimo

Small Blue larva, Magdalen Hill Down, 22/07/2015

Photo © Pauline

Small Blue - larva - Magdalen Hill Down - 11-Jul-12

Photo © Pete Eeles

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The pupa is attached to a grass blade, leaf, or other vegetation, where it is attached to a silk pad by a silk girdle and the cremaster. This stage lasts between 1 and 3 weeks, depending on temperature.

Cupido minimus - Pupa [Wolfgang Wagner]

Photo © Wolfgang Wagner

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Description to be completed.

Click here to see the aberration descriptions and images for this species.

Similar Species

Holly Blue

Description to be completed.


Watch Video

The following links provide additional information on this butterfly.


The species description provided here references the following publications:

Fuessly (1775) Fuessly, J.K. (1775) Verzeichniss Der Ihm Bekannten Schweizerischen Insekten.
Leach (1815) Leach (1815) In Brewster: The Edinburgh Encyclopaedia.
Schrank (1801) Schrank, F. (1801) Fauna boica. Durchgedachte Geschichte der in Baiern einheimschen und zahmen Thiere.
Swainson (1827) Swainson, W. (1827) A Sketch of the Natural Affinities of the Lepidoptera Diurna of Latreille. The Philosophical magazine : or Annals of chemistry, mathematics, astronomy, natural history and general science.