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Common Blue

Photograph by: 
Peter Orchard

A common species seen from early June until late October. It likes rough, open ground (especially chalk downland) where they can find an abundance leguminous flowers. 


  • Common Blue: peas and beans

    Post date: Wednesday, 3 June, 2015 - 00:00

    Blues can be tricky chaps to sort out; the silvery underside with orange dots is a familiar feature amongst many of the family. You have to take various factors in to account when separating them.

    The common blue (Polyommatus icarus) is on the wing from early June right through until late October as they have more than one brood which overlap giving an almost continual presence during the summer and early autumn. Other similar species tend to be more limited in their flying season.

    The common blue is certainly more common than most other species of blue (unless you are in Purbeck where, in places, the Adonis blue is now as common, if not more so) and so it is the most likely one you will see. It likes rough, open ground, especially chalk downland, where they can find an abundance of clovers, medicks, trefoils, restharrows and other leguminous flowers; other species tend to be a bit more restricted in their preferences. In good years, population wise, it is not uncommon for this butterfly to find its way into gardens.

    Finally, size can help too; the common blue larger than most of the other frequently encountered blue species but still a little smaller than the Adonis blue. Remember, too, that the Adonis has a much more vivid blue colouration. 


  • Where have all the common blues gone?

    Post date: Monday, 3 August, 2015 - 00:00

    "Their name suggests that they should be a familiar sight, but numbers of common blue butterflies in recent years have reached an all time low. Why have they declined so drastically? The answer is all that too familiar story of habitat loss'"

    Read the full article on the BBC Earthwebsite about research into this growing issue with the common blue ... 


  • Common Blue in Dorset: what your tweets tell us ...

    Post date: Friday, 26 April, 2019 - 21:19

    Not so long ago, if you saw a blue butterfly in the countryside you would have to think "Why is that NOT a common blue?" Living up to its name it was certainly the most common of the blues but that seems to have changed in the last couple of years with its numbers seemingly much lower now; in places Adonis blue and silver-studded blue seem to outnumber the common blue. The common blue can be found in a wide range of habitat types from flower-strewn grassland and meadows, hedgerows, woodland glades, heathland, parks and occasionally gardens. Generally double brooded down here in Dorset in good years they are known to have three broods meaning they can be seen from May into October and sometimes even later; there is a gap in June between the first and second broods.

    We have fifty eight records for 2017 and 2018 in the Nature of Dorset database and there are records for almost every week from week 16 in late April to week 44 at the end of October. In June 2017 there was the inter-brood gap with just one record that month but in 2018 it seems July was the gap month with far less records than the previous July. With far more seen in May 2017 than May 2018 it seems that emergence was later in 2018 meanuing the second brood was later too.

    Seventy four sites have reports of common blue and whilst chalk grassland sites feature well in the list there are also heathland sites as well as woodland. Durlston, Badbury Rings and Ballard Down all have several reports of common blue and these all have a calcareous rock base.


Common Name Common Blue
Scientific Name Polyommatus icarus
Species Group Lycaenid Butterflies Blues and Hairstreaks
Interest Level
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Identification Notes
Primary Habitat
Preferred Environment
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Additional Identification Notes
Similar Species

The records for this species have been organised into reports, charts, maps and photos. Click a pic below to see the detail:

Notebook Distribution Map Sites List Some Charts Some Photographs Recent Records Guidance Notes

To see related species click here: 

Lycaenid Butterflies Blues and Hairstreaks