Adonis Blue

Polyommatus bellargus (po-lee-oh-MAY-tuss bell-AH-guss)

Adonis Blue - Bonchurch Down IOW 27.05.2014
Photo © Neil Freeman

30 - 40mm

Checklist Number

Family:LycaenidaeLeach, 1815
Subfamily:PolyommatinaeSwainson, 1827
Tribe:PolyommatiniSwainson, 1827
Genus:PolyommatusLatreille, 1804
Subgenus:LysandraHemming, 1933
Species:bellargus(Rottemburg, 1775)

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The Adonis Blue is a species of chalk downland, where it may be found in warm, sheltered spots. The male Adonis Blue has brilliantly-coloured blue wings that gives this butterfly its name, and can be found flying low over vegetation, seeking out the less-conspicuous females that are a rich chocolate brown in colour. Like its close relative, the Chalk Hill Blue, the distribution of this species follows the distribution of Horseshoe Vetch which, in turn, follows the distribution of chalk and limestone grassland. However, this species has a more restricted distribution than the Chalk Hill Blue, indicating more precise habitat requirements. This butterfly can be found in large numbers where it does occur, such as the chalk downloads of Dorset, South Wiltshire, West Sussex, East Sussex and East Kent. This species is absent from central England, northern England, Wales, Scotland, Ireland, the Isle of Man and the Channel Islands. This species lives in discrete colonies.

Taxonomy Notes

There is considerable variation in this species, especially with regard to the amount of blue scaling on the upperside of the female. This variation has resulting a number of named subspecies and forms, although only the nominate species is recognised here.

  • Verity (1919) described the English race as ssp. brittanorum, with a type locality of Cuxton in Kent. It was said to differ from the nominate subspecies in the greater amount of blue and smaller and less vivid lunules in the female, and a darker underside that is less frequently tinged with fulvous in the male, the black dots on the underside also being smaller. The description is to be found under Agriades thetis, an earlier scientific name for the Adonis Blue.
  • Verity (1919) also singled out a particular race from Ventnor on the Isle of Wight, which he named ssp. vestae, where the adults were small, the male appearing more silvery and with, in most cases, a series of premarginal black dots, and the female with greatly reduced, sometimes absent, orange lunules on the upperside which are very pale on the underside of both sexes. The underside of both sexes is also very dark.
  • Verity (1934) also described f. antebrittanorum to represent the Spring generation of the English race brittanorum which, according to Verity, is separable by androconial differences.

Polyommatus bellargus

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

Adonis Blue male - Mill Hill, Sussex 29-Aug-2013

Photo © Neil Hulme

Adonis-Blue- 5D34448 Larden Chase 23 August 2013

Male Underside
Photo © IainLeach

Adonis Blue female - Mill Hill, Sussex 19-May-2010

Photo © Neil Hulme

Adonis-Blue-Martin Down 21 May 2011 03C0831

Female Underside
Photo © IainLeach

Photo Album ...

Conservation Status

This butterfly is dependent on unimproved calcareous grassland and has suffered from both loss of habitat as well as inappropriate habitat management. It is therefore considered a species of conservation concern.

UK BAP StatusDistribution Trend (%)Population Trend (%)
Species of Conservation Concern

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).


This is a warmth-loving species, preferring sheltered, south-facing slopes. This species is found where the turf is closely-cropped, possibly because it provides a higher temperature for the immature stages or because this is a requirement for the ant species that attend the Adonis Blue larva and pupa. The loss of grazing by rabbits, for example, causes the sward to become overgrown and can render a site unsuitable for this species.



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

There are two broods each year. The first adult emergence is in the second half of May, peaking at the end of May and beginning of June. The second adult emergence is in the second half of August, peaking at the end of August and beginning of September.

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.


The sexes are strongly dimorphic; the males being a magnificent electric blue, and the females being a chocolate brown. The adults live in concentrated colonies and appear to have limited powers of dispersal. However, on good sites, this species can be found by the hundred. This species can be found roosting communally at night.

Adults feed primarily on Marjoram (Origanum vulgare) and Ragwort (Senecio jacobaea).

Photo Album ...


Eggs are laid singly, typically on the underside of terminal leaves of the foodplant. A preference is shown for small sprigs of foodplant growing in short turf. Eggs laid in May or June hatch in a week or two, whereas those laid in August and September can take several weeks longer.

Adonis Blue - ovum - Godlingstone Hill - 90 [Tim Norriss]

Photo © Tim Norriss

Adonis Blue - ovum - Figsbury Ring - 19-Jun-13

Photo © Pete Eeles

Adonis Blue ovum - Found - Ballard Down, Swanage 16.06.14

Photo © Tony Moore

Adonis Blue - Ovum - Durlston Country Park - 20-Sep-2012

Photo © Coopera

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The larvae are green with yellow stripes running along the length of the body. Unlike its close relative, the Chalkhill Blue, the larva of the Adonis Blue feeds by day. The larva has a Newcomer's gland in the 7th segment which provides secretions that are attractive to ants. This is a symbiotic relationship for, like many other blues, the Adonis Blue larva (and pupa) is afforded protection by the ants from parasites and other predators.

Early instars feed by grazing on one side of the leaf, leaving the epidermis of the other side intact. When not feeding, the larva rests at the base of the foodplant, often on bare soil. Ants are known to bury the larva in a cell in the earth, where the ants continue to "milk" it for secretions. If not overwintering, this stage lasts around a month.

The primary larval foodplant is Horseshoe Vetch (Hippocrepis comosa).

Adonis Blue - larva - Thatcham - 08-Sep-07 (1195) {REARED}

Photo © Pete Eeles

Adonis Blue larva - Mill Hill, Sussex  14-April-2011

Photo © Neil Hulme

Adonis Blue larva -  Mill Hill, Sussex  14-April-2011

Photo © Neil Hulme

Adonis Blue Larva - Durlston CP - 26-7-08

Photo © Gwenhwyfar

Photo Album ...


The pupa is formed on the ground, often in a small hollow or crevice. Ants are known to bury the pupa in a chamber in the earth that is connected to the ants' nest, where it is constantly attended by ants. This stage lasts around 3 weeks.

Adonis Blue - pupa - Thatcham - 06-Oct-04 [REARED]

Photo © Pete Eeles

Photo Album ...


Although far more consistent in colour and marking than its close relative the Chalk Hill Blue, the Adonis Blue is a considerably variable butterfly nonetheless.

In common with other members of the family, this species demonstrates much variation in the number, size and orientation of the underside spotting, ranging from the extremes of ab. Krodeli (absence of spotting to the underside) to heavily striated examples where the familiar spots are greatly extended into black streaks (ab. striata).

The blue of the male upperside can also vary; in some examples there is a distinctly green tint to the wings (ab. viridescens) while others are sometimes of a pale shade (ab. pallida). A grey-blue colouration is known as ab. suffusa and examples where the typical blue colour is replaced by a blue-black shade are known as ab. nigra.

The blue form of the female in which the blue scaling extends over the fore and hind wings obliterating the brown ground colour except along the costa and outer margins, and with orange lunules present on all wings is called ab. ceronus. Where the orange lunules are present on the hindwings only this is referred to as ab. semiceronus. The amount of blue on the female is subject to much variation and at first may appear random, with each 'blue female' appearing different from the next, however, once you start looking at these females closely you begin to see that the same traits do occur again and again, and all of a sudden the distribution of blue scales and development of the lunules is far from random but actually made up of a finite series of recognisable and repeating characteristics. It is these repeating characteristics that enables us to name these aberrations from descriptions made over a century ago. The blue aberrations of the female Adonis Blue are more frequently met with in the spring brood, suggesting an environmental trigger at the heart of these suffusions.

Very rarely this species is known to hybridise with its close relative the Chalkhill Blue, resulting in specimens that bare traits from each species and a colouration that appears (in the male) to be half way between each species in their typical forms. This butterfly is traditionally known as ab. polonus, although being a hybrid it is not an aberration as such at all. Strictly speaking it should probably be known as bellargus x coridon. It is well worth looking out for this hybrid at sites where both species fly together. Polonus is encountered within the spring brood of Adonis Blue.

Gynandromorphs occur in this species but are rare. Occasionally female specimens will be found with strong streaks of male colouration on one or more wings (sexual mosaics or mixed gynandromorphs) and very rarely halved gynandromorphs are encountered where the butterfly exhibits male colouration on one side, and female colouration on the other, even on the abdomen.

There are 109 named aberrations known to occur in Britain.

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

Similar Species

Brown Argus

Description to be completed.

Chalkhill Blue

The female Adonis Blue is easily mistaken for a female Chalkhill Blue and the two species occasionally fly together toward the second half of August on some sites. Distinguishing the two is not at all easy. One guideline is that the pale scales on the hindwings, between the red dots and the white fringe, are blue in a female Adonis Blue, and white in a female Chalkhill Blue.

Adonis Blue female (left) and Chalkhill Blue female (right)

Common Blue

The male Adonis Blue is often mistaken for a male Common Blue. However, the two can be distinguished by looking at the white fringes of the wings. Only on the Adonis Blue are the fringes intersected by black bands. This diagnostic can also be used to distinguish the two species based on their undersides.

Adonis Blue male (left) and Common Blue male (right)

Northern Brown Argus

Description to be completed.


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The following links provide additional information on this butterfly.


The species description provided here references the following publications:

Hemming (1933) Hemming, F. (1933) Holarctic Butterflies: Miscellaneous Notes on Nomenclature. The Entomologist.
Latreille (1804) Latreille, P.A. (1804) Nouveau Dictionnaire d'Histoire Naturelle.
Leach (1815) Leach (1815) In Brewster: The Edinburgh Encyclopaedia.
Rottemburg (1775) von Rottemburg, S.A. (1775) Der Naturforscher.
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.
Verity (1919) Verity, R. (1919) Seasonal Polymorphism and Races of some European Grypocera. Entomologist's Record and Journal of Variation.
Verity (1934) Verity, R. (1934) The Lowland Races of Butterflies of the Upper Rhone Valley. Entomologist's Record and Journal of Variation.