Wingspan
29 - 36mm |
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Common Blue
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Polyommatus icarus
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Rottemburg, 1775 |
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Ref: 1574 |
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| Superfamily: | Papilionoidea |
| Family: | Lycaenidae |
| Subfamily: | Lycaeninae |
| Genus: | Polyommatus |
| Subgenus: | |
| Species: | icarus |
| Subspecies: | icarus (Rottemburg, 1775) | | | mariscolore (Kane, 1893) |
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Male |
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Male Underside |
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Female |
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Female Underside |
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As its name suggests, 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. Subspecies: icarus This subspecies inhabits most of the British Isles, with the exception of Ireland. Subspecies: mariscolore This subspecies represents the population found in Ireland. The female of this subspecies has larger areas of blue, and larger orange spots, than those found in the subspecies icarus.
This is the most widespread Lycaenid found in the British Isles and can be found almost anywhere, including the Orkneys. It is absent, however, from the northern Shetlands and the mountainous areas of Wales and Scotland. It forms reasonably discrete colonies measured in tens or hundreds, with individuals occasionally wandering some distance.
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. Subspecies: icarus 
Subspecies: mariscolore 
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.
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.
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).
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. Subspecies: icarus
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Common Blue male
Ryton Pools Country Park
Warwickshire
8th August 2009 Photo © millerd |
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Subspecies: mariscolore
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Common Blue - Female Upperside - 12/07/2008, Hogstown Bog, Co Down, Northern Ireland Photo © Dave McCormick 12-Jul-2008 |
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Common Blue - Female Upperside - 12/07/2007, Whitespots Country Park, Co Down, Northern Ireland Photo © Dave McCormick 12-Jul-2007 |
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Common Blue - Male Upperside - 12/07/2009, Hogstown Bog, Co Down, Northern Ireland Photo © Dave McCormick 12-Jul-2009 |
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Common Blue - Courting Pair- 16/06/2009, Mountstewart, Co Down, Northern Ireland Photo © Dave McCormick 16-Jun-2009 |
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Description to be completed
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Common Blue - Male Underside - 12/07/2007, Whitespots Country Park, Co Down, Northern Ireland. Minor ab, spots on underside are slightly different than normal. Photo © Dave McCormick |
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Common Blue (bilateral gynandromorph) Holyrood park,Edinburgh 09th July 2009
While clicking snaps of a Small Tortoiseshell and some Meadow Browns at Holyrood Park in Edinburgh on the 9th of July 2009, I came across this unusual blue butterfly - I understand it is a Common Blue (Polyommatus icarus) - what made it unusual was that while I was taking photos of it with open wings I noticed that one of its wings was coloured like a male - while the other had a female wing pattern. It's a perfect bilateral gynandromorph specimen. Photo © sahil |
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The white bun-shaped eggs are quite visible and can be easily found on good sites. This stage lasts just over a week.
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 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.
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 do the fringes contain black bands.
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| Male Adonis Blue |
Male Common Blue |
The Brown Argus and Common Blue can be differentiated from their undersides, since the Brown Argus lacks a spot on the underside of the forewing that is present in the Common Blue.
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| Brown Argus |
Common Blue |
The Brown Argus and female Common Blue can be difficult to tell apart from their uppersides. However, the Brown Argus is completely lacking in blue scales, but may have a blue sheen. The highly-variable female Common Blue, on the other hand, always has some blue scaling, especially close to the body.
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| Brown Argus |
Common Blue (female) |
Description to be completed
Description to be completed
The Northern Brown Argus and Common Blue can be differentiated from their undersides, since the Northern Brown Argus lacks a spot on the underside of the forewing that is present in the Common Blue.
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| Common Blue |
Northern Brown Argus |
The Northern Brown Argus and female Common Blue can be difficult to tell apart from their uppersides. However, the Northern Brown Argus is completely lacking in blue scales, but may have a blue sheen. The highly-variable female Common Blue, on the other hand, always has some blue scaling, especially close to the body.
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| Common Blue (female) |
Northern Brown Argus |
Description to be completed
Click here to see the distribution of this species overlaid with specific site information. Alternatively, select one of the sites listed below. |
 | Bedfont Lakes Country Park LNR, Durlston Country Park, Ellerburn Bank, Gait Barrows, Howardian Local Nature Reserve, Hutton Roof Crags, Linn Dean, Mill Hill |  | Bishop Middleham Quarry, Denbies Hillside, Devils Ditch, Glenarm, Leighton Moss, Thurlbear Quarrylands, Whitbarrow NNR, Whitecross Green Wood |  | Aberffraw Dunes, Banstead Downs, Fleam Dyke |  | Stockbridge Down |  | | | Not rated | Arnside Knott, Ashampstead Common, Hounslow Heath LNR, Hyde, Loch Ard Forest, Mayford Pond |
Despite a general decline in distribution, this butterfly remains widespread and is not currently a species of conservation concern. |
| Not Listed |  |  |
From The State of Butterflies in Britain and Ireland and the UK Biodiversity Action Plan (UK BAP) (2007 review).
The following links provide additional information on this butterfly.
The species description provided here has been derived from the author's own observations and the information contained in the following works:
- A Natural History of British Butterflies, by F.W.Frohawk.
- British and Irish Butterflies, by Adrian M. Riley
- South's British Butterflies, by T.G.Howarth (which is based extensively on the classic work, "The Butterflies of the British Isles", by Richard South).
- The Butterflies of Britain and Ireland, by Jeremy Thomas and Richard Lewington.
- The Millennium Atlas of Butterflies in Britain and Ireland, by Jim Asher, Martin Warren, Richard Fox, Paul Harding, Gail Jeffcoate, Stephen Jeffcoate.
- The Moths and Butterflies of Great Britain and Ireland Volume 7 (1) Hesperiidae to Nymphalidae (the Butterflies), by A. Maitland Emmet and John Heath (editors).
- The State of Butterflies in Britain and Ireland, Richard Fox, Jim Asher, Tom Brereton, David Roy and Martin Warren.
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