Common Blue

Polyommatus icarus (po-lee-oh-MAY-tuss IK-uh-russ)

Common Blue male - Shadowbrook Meadows Solihull 21.05.2014
Photo © Neil Freeman
 

Wingspan
29 - 36mm

Checklist Number
61.018

Family:LycaenidaeLeach, 1815
Subfamily:PolyommatinaeSwainson, 1827
Tribe:PolyommatiniSwainson, 1827
Genus:PolyommatusLatreille, 1804
Subgenus:PolyommatusLatreille, 1804
Species:icarus(Rottemburg, 1775)
Subspecies:icarus (Rottemburg, 1775)
 mariscolore (Kane, 1893)

< Previous SpeciesNext Species >

Introduction

Living up to its name, this butterfly is the commonest blue found in the British Isles. While the male has bright blue uppersides, the female is primarily brown, with a highly variable amount of blue. This is the most widespread Lycaenid found in the British Isles and can be found almost anywhere, including Orkney. It is absent, however, from Shetland and the mountainous areas of Wales and Scotland. This butterfly forms reasonably discrete colonies measured in tens or hundreds, with individuals occasionally wandering some distance.

Taxonomy Notes

Oberthür (1910) described the English race of Common Blue as ssp. tutti. In comparison with the continental race, the English race is said to have less rounded forewings that are lengthened, a male underside that is a deeper grey in tint, and uppersides that have a more transparent blue and pink sheen. Females are generally blue with orange marginal lunules punctuated by black, especially on the hindwings, and a tendency for the colour to lighten to white near the apex of the forewings. Oberthür came to his conclusions based on 150 specimens from North Scotland, Rannoch, Cheshire, North Devon, the New Forest, North Kent, Folkestone, Dover, Glengariff and County Kerry in Ireland, and from various collections.

Graves (1930b) also described f. postclara of ssp. mariscolore that is used to represent the second generation that occurs in some parts of Ireland. In comparison with the first generation, both sexes have more tapered forewings and are slightly smaller. The male upperside is brighter and the underside of a lighter grey. The female upperside is paler at the apex of the forewings and the submedial area of the hindwings. The female underside has less metallic blue-green scaling on the bases of the hindwings.

Polyommatus icarus ssp. icarus

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

The nominate subspecies is found throughout England, Scotland, Wales, the Isle of Man and the Channel Islands. It may also be found in some parts Ireland, although there is some confusion regarding its status, as discussed under the subspecies mariscolore.

Common Blue male - Chantry Hill, Sussex 6-Aug-2013

Male
Photo © Neil Hulme

Common Blue - Brockham Quarry,Surrey - 10.05.2015

Male Underside
Photo © Buchan Boy

Common Blue Female - Crawley, Sussex 17-June-05

Female
Photo © Vince Massimo

Common Blue female - Chantry Hill, Sussex 6-Aug-2013

Female Underside
Photo © Neil Hulme

Photo Album ...


Polyommatus icarus ssp. mariscolore

This subspecies was first defined in Kane (1893) as shown here (type locality: Ireland).

Kane first hinted that such a subspecies existed in his European Butterflies [Kane (1885)] where he says "Often the females of L.Bellargus [Adonis Blue] and Icarus [Common Blue] are indistinguishable, and a female form of the latter occurs corresponding to v. (female) Ceronus of the former. Occasionally the male of L.Icarus also assumes a more vivid blue, as in Spain, etc., and the blk. ray points extend slightly into the fringe."

In his definition of mariscolore, Kane (1893) refers to South (1887) who makes similar observations with a direct reference to Irish and Scottish specimens: "Male ... Fig.2 shows a male icarus, closely approaching male bellargus in colour; and fig.3 a decidedly violet specimen. These two last are from Ireland, and were kindly sent me, together with others, ... by Mr. Percy Russ, of Culleenamore, Sligo. Several of the males from Sligo exhibit a tendency to the bellargus coloration, but the one figured is the most decided. The only other locality from which I have seen similar examples is the Isle of Hoy, but these are not quite so striking as the Sligo specimens, and the bellargus colour is mostly confined to the inferior wings. In typical icarus the hind margins of all the wings have a linear black border; this in English specimens does not usually attract one's attention, but in Scotch and Irish examples it is sometimes very conspicuous ... In a few of the Sligo specimens there is a distinct row of black spots on the inferior wings internal to the marginal border. Female ... Some female icarus from Pitcaple, Aberdeenshire; and others from Castletown, Co. Cork, Ireland ... are very handsome. The blue, which in these specimens is of a violet tint, suffuses nearly the whole of the wings up to the large and bright orange crescents. These last are almost confluent, and consequently the orange marking appears band-like, as shown in the Scotch example, Pl.II., fig.6 ... Both sexes of Irish and Scotch are uniformly larger than English specimens".

Ford (1945) makes an additional observation regarding the wing shape, saying "In Ireland, however, occurs a characteristic and brilliant sub-species which has arisen in isolation there. The specimens are large and tend to have rather pointed wings, while the females are heavily marked with blue, and the orange crescents along the outer margin of their wings are exceptionally well developed". Ford (1945) also claims that "gynandromorphs are very much more frequent in the Irish than the British race".

The distribution of the subspecies mariscolore is a confusing one. In describing mariscolore-like features, both South (1887) and Kane (1893) make reference to both Irish and Scottish specimens. Indeed, Dennis (1977) states that "The most exaggerated development of the subspecies the writer has seen is from Burray and mainland Orkney - extremely large insects ... with large, bright red lunules on the upperside of the female". Thomson (1980) confirms that a race "resembling" mariscolore is found in north and west Scotland but that "subspecific differentiation without a careful analysis of all the factors and characters involved is not considered to be justified". Thomas & Lewington (2010) state that mariscolore is found both in Ireland and in north-western Scotland. When it comes to Ireland, Nash (2012) suggests that both ssp. mariscolore and ssp. icarus are found there. It is certainly true that not all Irish Common Blues conform to the description of mariscolore, which is characterised by the amount of blue in the female, since many individuals are brown with a variable amount of blue. Riley (2007), however, seems to take a different position from all other authorities, stating that mariscolore is "Restricted to Ireland where it is widespread and common" and is the only subspecies found there, but gives no explanation for this position. Aldwell & Smyth (2015) say that "In Donegal the female Common Blue, most frequently observed, is the beautiful subspecies mariscolore", suggesting that this is not the only subspecies found. The authors go on: "It is also found in NW Scotland and parts of Scandinavia which suggests that the colouration is temperature-influenced", but give no explanation for this assumption or provide any analysis of the temperature difference with other regions.

The subspecies mariscolore differs from the subspecies icarus as follows:

  • 1. Generally larger in size, especially the female.
  • 2. The upperside of the female has extensive patches of blue, with large and bright orange marginal spots.

Polyommatus icarus ssp. mariscolore (Kane, 1893)

In the first place, the Irish butterfly usually considerably exceeds in size that of England, varying from about 1 inch 2 lines to 1.5 inches in the June emergence; but the individuals of the second emergence are much smaller, and generally conform much more nearly to the usual English type in both sexes, to which, therefore, I need not further refer. Probably referable to var. pusillus, Gerhard (cf. Dale's 'British Butterflies'). Mr. South notes that the Irish and Scotch icarus are similarly characterised by their large size, and the brilliant blue of the female bordered with bright orange marginal ocelli ...

The female offers the most conspicuous divergence from the normal English and Continental type, in which the basal half only is dusted with blue scales (fig.8), the brown of the upper side being widely replaced by a violet or occasionally wholly by the bright blue of L. bellargus. These forms are not uncommon in Ireland, in Galway, Sligo, Donegal, Antrim, Down, Westmeath, Waterford, &c., and are accompanied by a series (often almost confluent) of very bright orange peacock-eye markings on the outer margins of all wings, so that some specimens (if not too brilliant) would pass muster as the var. ceronus of L. bellargus (fig. 12); another most interesting testimony to the genetic affinities of this species. This var. ceronus of icarus occurs in some abundance at Ballynahinch, Connemara, and at Ardrahan and other parts of Galway, as well as in some central and southern localities ...

Taking a general view of the foregoing, we note, firstly, that the Scotch and Irish races are unusually large (Mr. Jenner Weir notes the Orkney insect being "unexpectedly large," 1 inch 5 lines - Ent. xiv. 3), that they vary in parallel directions from the English type, and present as numerous genetic characters linking them to other species as do the latter; and in the female sex have acquired generally a very remarkable one in addition, and instance of gynandrochromism. It may be that the acquisition of more brilliant colours in the female may be of advantage under less sunny skies, where the sun-loving Rhopalocera have less opportunities of selecting their mates, and cannot afford to indulge in long engagements ...

I have not heard that this Irish variety of the female has been recorded as a local form from the Continent; and as it is an important parallel variation to that of L.bellargus and var.syngrapha of L.corydon, think it may receive the varietal name of mariscolore.

[The counties mentioned in this definition are shaded green in the image below.]

Highslide JS
Common Blue ssp. mariscolore - male - Craigavon Lakes, Northern Ireland - 11-Jun-14-10

Male
Photo © Pete Eeles

Common Blue ssp. mariscolore - male - Craigavon Lakes, Northern Ireland - 11-Jun-14-7

Male Underside
Photo © Pete Eeles

Common Blue ssp. mariscolore - female - Craigavon Lakes, Northern Ireland - 11-Jun-14-11

Female
Photo © Pete Eeles

Common Blue ssp. mariscolore - female - Craigavon Lakes, Northern Ireland - 11-Jun-14-13

Female Underside
Photo © Pete Eeles

Photo Album ...


Conservation Status

Despite a general decline in distribution, this butterfly remains widespread and is not currently a species of conservation concern.

UK BAP StatusDistribution Trend (%)Population Trend (%)
Not Listed
Stable-6
Decrease-30

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).

Habitat

This species is found in a wide variety of habitats, including unimproved grassland such as roadside verges and waste ground, downland, woodland clearings, heathland and even sand dunes.

Distribution

 

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

This species has 2 broods in the southern counties of England, and 1 brood further north. There may be a 3rd brood in favourable years. Time of emergence is highly variable. In good years, adults may be seen as early as the middle of May on more southerly sites. These peak at the end of May, giving rise to a second generation that emerges in the second half of July, peaking in the middle of August. Colonies in northern England and Scotland typically have a single brood that emerges in June, reaching a peak in July.

Polyommatus icarus ssp. icarus

Polyommatus icarus ssp. mariscolore

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.

Imago

This species is most active in sunshine and is a frequent visitor to flowers. Males are the more active of the two sexes and set up territories which they patrol in search of females. The female is less conspicuous, spending most of her time nectaring, resting and egg-laying. When egg-laying, the female makes slow flights, low over the ground, searching out suitable foodplants on which to lay. When a suitable plant is located, a single egg is laid on the upperside of a young leaf.

In dull weather this species roosts head down on a grass stem. As for similar species, such as the Brown Argus, this species roosts communally at night, with several individuals occasionally found roosting on the same grass stem.

Adults feed primarily on Bird's-foot Trefoil (Lotus corniculatus), Bugle (Ajuga reptans), Carline Thistle (Carlina vulgaris), Fleabane (Pulicaria dysenterica), Kidney Vetch (Anthyllis vulneraria), Knapweeds (Centaurea spp.), Marjoram (Origanum vulgare), Ragwort (Senecio jacobaea), Thistles (Cirsium spp. and Carduus spp.), Thyme (Thymus polytrichus), Vetches (Vicia spp.) and White Clover (Trifolium repens).

Polyommatus icarus ssp. icarus

Common Blue Male - Crawley, Sussex 18-May-05

Photo © Vince Massimo
18-May-2005

Common Blue Male - Rusper Road,Crawley 17th May 2014

Photo © Buchan Boy
17-May-2014

Common Blue - imago - Hartslock - 10-May-08 (1)

Photo © Pete Eeles
10-May-2008

Common-Blue- 1DX7356. Lincs. August 2015

Photo © IainLeach

Common-Blue- 5D38428 Lincs June 2013

Photo © IainLeach

Common Blue - Penhale, Cornwal 21-Sept-2014 [Paul Fenn]

Photo © Paul Fenn

Common Blue pair - Cissbury, Sussex 21-July-2010

Photo © Neil Hulme
21-Jul-2010

Common Blue female - Shipton Bellinger - 4th August - 2014

Photo © Maximus
04-Aug-2014

Common Blue male - Chantry Hill, Sussex 6-Aug-2013

Photo © Neil Hulme
06-Aug-2013

Common Blues roosting  Stanwell Moor Middlesex  23rd August 2012

Photo © millerd
23-Aug-2012

Common-Blue- 5D38526 Lincs June 2013

Photo © IainLeach

Common Blue Female - Chaldon, Surrey 5-Aug-10

Photo © Vince Massimo
05-Aug-2010

Common Blue male - Great Yarmouth north dunes 30.05.2012

Photo © Neil Freeman
30-May-2012

Common Blue Female (Variant) - Chaldon, Surrey 22-Aug-11

Photo © Vince Massimo
22-Aug-2011

Common Blue male - Shadowbrook Meadows Solihull 21.05.2014

Photo © Neil Freeman
21-May-2014

Common Blue Dew - Larkhill - 04-09-2013

Photo © Wurzel
04-Sep-2013

Common Blue - imago - Greenham Common - 10-Jun-13-11

Photo © Pete Eeles

Common Blue Female - Chaldon, Surrey 5-Aug-10

Photo © Vince Massimo
05-Aug-2010

Common Blue - imago - The Holies - 31-May-10 (1)

Photo © Pete Eeles
31-May-2010

Common Blue - imago - Greenham Common - 19-Aug-12

Photo © Pete Eeles

Photo Album ...


Polyommatus icarus ssp. mariscolore

Common Blue ssp. mariscolore - female - Craigavon Lakes, Northern Ireland - 11-Jun-14-15

Photo © Pete Eeles
11-Jun-2014

Common Blue - female - The Raven, Co. Wexford, Ireland - 12-Aug-13-4

Photo © Pete Eeles
ssp.mariscolore distribution uncertain
12-Aug-2013

Common Blue ssp. mariscolore - male - Craigavon Lakes, Northern Ireland - 11-Jun-14

Photo © Pete Eeles
11-Jun-2014

Common Blue ssp. mariscolore - male - Craigavon Lakes, Northern Ireland - 11-Jun-14-7

Photo © Pete Eeles
11-Jun-2014

Common Blue ssp. mariscolore - female - Craigavon Lakes, Northern Ireland - 11-Jun-14-13

Photo © Pete Eeles
11-Jun-2014

Common Blue - imago - North Bull Island, Dublin, Ireland - 12-Jun-13-4

Photo © Pete Eeles
ssp.mariscolore distribution uncertain

Common Blue ssp. mariscolore - female - Craigavon Lakes, Northern Ireland - 11-Jun-14-12

Photo © Pete Eeles
11-Jun-2014

Common Blue ssp. mariscolore - female - Craigavon Lakes, Northern Ireland - 11-Jun-14-14

Photo © Pete Eeles
11-Jun-2014

Common Blue ssp. mariscolore - female - North Bull Island, Dublin, Ireland - 11-Jun-14

Photo © Pete Eeles
11-Jun-2014

Common Blue ssp. mariscolore - male - Craigavon Lakes, Northern Ireland - 11-Jun-14-8

Photo © Pete Eeles
11-Jun-2014

Common Blue ssp. mariscolore - male - Craigavon Lakes, Northern Ireland - 11-Jun-14-6

Photo © Pete Eeles
11-Jun-2014

Common Blue - female - The Raven, Co. Wexford, Ireland - 12-Aug-13

Photo © Pete Eeles
ssp.mariscolore distribution uncertain
12-Aug-2013

Common Blue ssp. mariscolore - female - Craigavon Lakes, Northern Ireland - 11-Jun-14-17

Photo © Pete Eeles
11-Jun-2014

Common Blue - imago - Ballyteigue Burrow Nature Reserve, County Wexford, Ireland - 20-Aug-13

Photo © Pete Eeles
ssp.mariscolore distribution uncertain
20-Aug-2013

Common Blue ssp. mariscolore - female - Craigavon Lakes, Northern Ireland - 11-Jun-14-16

Photo © Pete Eeles
11-Jun-2014

Common Blue ssp. mariscolore - female - Craigavon Lakes, Northern Ireland - 11-Jun-14-10

Photo © Pete Eeles
11-Jun-2014

Common Blue - imago - North Bull Island, Dublin, Ireland - 13-Jun-13-5

Photo © Pete Eeles
ssp.mariscolore distribution uncertain

Common Blue ssp. mariscolore - female - Craigavon Lakes, Northern Ireland - 11-Jun-14

Photo © Pete Eeles
11-Jun-2014

Common Blue - female - The Raven, Co. Wexford, Ireland - 12-Aug-13-3

Photo © Pete Eeles
ssp.mariscolore distribution uncertain
12-Aug-2013

Common Blue - imago - North Bull Island, Dublin, Ireland - 13-Jun-13

Photo © Pete Eeles
ssp.mariscolore distribution uncertain

Photo Album ...


Ovum

The white bun-shaped eggs are quite visible and can be easily found on good sites. This stage lasts just over a week.

Common Blue Egg freshly laid - Collard Hill, Somerset 2-June-2011

Photo © jamesweightman
03-Jun-2011

Common Blue Egg side view (laid on Rest Harrow) - Collard Down 2-June-2011 (Image taken 8-June-2011)

Photo © jamesweightman

Common Blue - ovum - Godlingstone Hill - Sep-90 [Tim Norriss]

Photo © Tim Norriss

Common Blue - ovum - Unknown location - 2004 (2) [REARED] [Reg Fry]

Photo © Reg Fry

Common Blue - ovum - Unknown location - 2004 [REARED] [Reg Fry]

Photo © Reg Fry

Common Blue (egg) - Stanwell Moor, Middlesex 1-Oct-2009

Photo © millerd

Common Blue (egg) - Stanwell Moor, Middlesex 1-Oct-2009

Photo © millerd

Common Blue - ovum - Greenham Common - 18-May-11 (1)

Photo © Pete Eeles

Common Blue - ovum - Greenham Common - 18-May-11 (2)

Photo © Pete Eeles

Common Blue - ovum - Greenham Common - 18-May-11 (3)

Photo © Pete Eeles

Common Blue ovum, Oxenbourne Down, 10/08/2015

Photo © Pauline
10-Aug-2015

Common Blue Ova - Somerset - 22/08/13

Photo © William
22-Aug-2013

Common Blue Ovum - Somerset - 29/08/13

Photo © William
29-Aug-2013

Common Blue ovum - Found near Stafford - Summer 2013.

Photo © Tony Moore
15-Aug-2013

Common Blue ovum, Bramshott Common, 05/06/2015

Photo © Pauline
05-Jun-2015

Photo Album ...


Larva

The larva emerges after a week or two. On emerging from the egg the larva moves to the underside of the leaf, where it feeds, by day, on the lower surface without breaking through the upper leaf surface. This leaves characteristic blotches on the foodplant that can give away the presence of a larva. More mature larvae feed more extensively on the leaves. Those larvae that overwinter do so in leaf litter at the base of the foodplant, changing from green to olive, resuming their green colouring in the spring.

Like many other species of blue, the larva is attractive to ants, although only in its last instar. There are 4 moults in total. If the larva does not overwinter, then this stage lasts around 6 weeks.

The primary larval foodplant is Bird's-foot Trefoil (Lotus corniculatus). Black Medick (Medicago lupulina), Common Restharrow (Ononis repens), Greater Bird's-foot Trefoil (Lotus pedunculatus), Lesser Trefoil (Trifolium dubium) and White Clover (Trifolium repens) are also used.

Common Blue Larva - Somerset - 12/07/15

Photo © William
12-Jul-2015

Common Blue Larva (3 days old) - Caterham, Surrey 14-Aug-11

Photo © Vince Massimo
14-Aug-2011

Common Blue Larva (21 days old) - Caterham, Surrey 1-Sept-11

Photo © Vince Massimo
01-Sep-2011

Common Blue - larva - Thatcham - 20-Apr-10 (1) {REARED}

Photo © Pete Eeles
20-Apr-2010

Common Blue 4th instar being attended by ants, Noar Hill, 08/04/2016

Photo © Pauline
08-Apr-2016

Common Blue larva, 7 days old, 28/08/2015 (reared)

Photo © Pauline
28-Aug-2015

Common Blue larva, 7 days old, 28/08/2015 (reared)

Photo © Pauline
28-Aug-2015

Common Blue Larva - Somerset - 27/08/13

Photo © William
27-Aug-2013

Common Blue - larva - Thatcham - 05-May-10 (1) {REARED}

Photo © Pete Eeles
04-May-2010

Common Blue Larva (17 days old) - Caterham, Surrey 28-Aug-11

Photo © Vince Massimo
28-Aug-2011

Common Blue Larva - Shedding Skin - Somerset - 31/08/13

Photo © William
31-Aug-2013

Common Blue Larva (post hibernation) - Caterham, Surrey 4-April-12

Photo © Vince Massimo
04-Apr-2012

Common Blue Larva - Somerset - Freshly Hatched - 28/08/13

Photo © William
28-Aug-2013

Common Blue Larva - Somerset - 27/07/15

Photo © William

Common Blue Larva (34 days old) - Caterham, Surrey 14-Sept-11

Photo © Vince Massimo
14-Sep-2011

Common Blue larva, 1 day old, 22/08/2015 (reared)

Photo © Pauline
22-Aug-2015

Common Blue - larva - Stockbridge Down - Jul-99 [Tim Norriss]

Photo © Tim Norriss

Common Blue Larva (1 day old with empty egg) - Caterham, Surrey 12-Aug-11

Photo © Vince Massimo
12-Aug-2011

Common Blue larva, 4 days old, 25/08/2015 (reared)

Photo © Pauline
25-Aug-2015

Common Blue Larva with eggshell Larva emerged 12-6-11 from egg laid 2-6-11

Photo © jamesweightman
12-Jun-2011

Photo Album ...


Pupa

The pupa is formed on the ground or, occasionally, at the base of the foodplant, under a few silk strands. The pupa is attractive to ants which may bury it in earth. This stage lasts around 2 weeks.

Common Blue - pupa - Stockbridge Down - Jul-99 [REARED] [Tim Norriss]

Photo © Tim Norriss

Common Blue - pupa - Thatcham - 03-Jun-10 (1) {REARED}

Photo © Pete Eeles
03-Jun-2010

Common Blue - pupa - Thatcham - 03-Jun-10 (2) {REARED}

Photo © Pete Eeles
03-Jun-2010

Common Blue - pupa - Thatcham - 03-Jun-10 (3) {REARED}

Photo © Pete Eeles
03-Jun-2010

Common Blue pupal cell - Caterham, Surrey 29-May-12

Photo © Vince Massimo
29-May-2012

Common Blue Pupa (11 days before hatching) - Caterham, Surrey 3-June-12

Photo © Vince Massimo
03-Jun-2012

Common Blue Pupa (3 days before hatching) - Caterham, Surrey 11-June-12

Photo © Vince Massimo
11-Jun-2012

Common Blue Pupa (2 days before hatching) - Caterham, Surrey 12-June-12

Photo © Vince Massimo
12-Jun-2012

Common Blue Pupa (1 day before hatching) - Caterham, Surrey 13-June-12

Photo © Vince Massimo
13-Jun-2012

Common Blue pupa (6 days old) - Caterham, Surrey 3-June-12

Photo © Vince Massimo
03-Jun-2012

Common Blue Pupa (6 days before hatching) - Caterham, Surrey 8-June-12

Photo © Vince Massimo
08-Jun-2012

Common Blue Pupa (4 days before hatching) - Caterham, Surrey 10-June-12

Photo © Vince Massimo
10-Jun-2012

Common Blue Pupa (3 days before hatching) - Caterham, Surrey 11-June-12

Photo © Vince Massimo
11-Jun-2012

Common Blue Pupa (2 days before hatching) - Caterham, Surrey 12-June-12

Photo © Vince Massimo
12-Jun-2012

Common Blue Pupa (1 day before hatching) - Caterham, Surrey 13-June-12

Photo © Vince Massimo
13-Jun-2012

Photo Album ...


Aberrations

Description to be completed.

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

Similar Species

Adonis 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)

Brown Argus

Of the two sexes, it is the female Common Blue that causes most confusion with the Brown Argus. The blue present in a female Common Blue is highly variable, with individuals ranging from almost completely blue through to completely brown. It is this latter colouring that causes the most confusion. Even so, the Brown Argus has no blue scales, but may give off a blue sheen from the wings and the hairs found on the thorax and abdomen. Another diagnostic is that the Brown Argus normally has a prominent dark spot in the centre of the forewings.


Brown Argus (left) and female Common Blue (right)

Differentiating Brown Argus and Common Blue from their undersides is even more problematic, and we need to resort to the pattern of spots. Here we have two distinguishing features. The first is that the Common Blue has a spot on the underside of the forewing that is absent in the Brown Argus. The second is that two of the spots on the leading edge of the hindwing are relatively-close in the Brown Argus, almost forming a "figure of eight", but are more spaced apart in the Common Blue. This diagnostic is particularly useful if the underside of the forewing isn't visible.


Brown Argus (left) and Common Blue (right)

Chalk Hill Blue

Description to be completed.

Holly Blue

Description to be completed.

Northern Brown Argus

Of the two sexes, it is the female Common Blue that causes most confusion with the Northern Brown Argus. The blue present in a female Common Blue is highly variable, with individuals ranging from almost completely blue through to completely brown. It is this latter colouring that causes the most confusion. Even so, the Northern Brown Argus has no blue scales, but may give off a blue sheen from the wings and the hairs found on the thorax and abdomen. Another diagnostic is that the Northern Brown Argus normally has a prominent dark spot in the centre of the forewings and, in the case of the artaxercxes subspecies of Northern Brown Argus, it a distinctive white dot. Any identification challenges are usually, therefore, with respect to the salmacis subspecies of Northern Brown Argus that does not have this white spot.


Common Blue female (left) and Northern Brown Argus ssp. salmacis (right)

Differentiating Common Blue and Northern Brown Argus from their undersides is even more problematic, and we need to resort to the pattern of spots. Here we have two distinguishing features. The first is that the Common Blue has a spot on the underside of the forewing that is absent in the Northern Brown Argus. The second is that two of the spots on the leading edge of the hindwing are relatively-close in the Northern Brown Argus, almost forming a "figure of eight", but are more spaced apart in the Common Blue. This diagnostic is particularly useful if the underside of the forewing isn't visible.


Common Blue (left) and Northern Brown Argus (right)

Silver-studded Blue

Description to be completed.

Videos


Watch Video
Watch Video

The following links provide additional information on this butterfly.

References

The species description provided here references the following publications:

ReferenceDetails
Aldwell & Smyth (2015) Aldwell, R. & Smyth, F. (2015) The Butterflies of Donegal.
Dennis (1977) Dennis, R.L.H. (1977) The British Butterflies - Their Origin and Establishment.
Ford (1945) Ford, E.B. (1945) Butterflies.
Graves (1930b) Graves, P.P. (1930) Notes on Collecting in Ireland. Entomologist's Record and Journal of Variation.
Kane (1885) Kane, W.F. de Vismes (1885) European Butterflies.
Kane (1893) Kane, W.F. de Vismes (1893) A catalogue of the Lepidoptera of Ireland. The Entomologist.
Latreille (1804) Latreille, P.A. (1804) Nouveau Dictionnaire d'Histoire Naturelle.
Leach (1815) Leach (1815) In Brewster: The Edinburgh Encyclopaedia.
Nash (2012) Nash, D., Boyd, T. and Hardiman, D. (2012) Ireland's Butterflies: A Review.
Oberthür (1910) Oberthür, C. (1910) Etudes de Lépidoptérologie comparée.
Riley (2007) Riley, A.M. (2007) British and Irish Butterflies: The Complete Identification, Field and Site Guide to the Species, Subspecies and Forms.
Rottemburg (1775) von Rottemburg, S.A. (1775) Der Naturforscher.
South (1887) South, R. (1887) Notes on the Genus Lycaena. The Entomologist.
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.
Thomas & Lewington (2010) Thomas, J. and Lewington, R. (2010) The Butterflies of Britain and Ireland. Edition 2.
Thomson (1980) Thomson, G. (1980) The Butterflies of Scotland.