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Brown Argus

Photograph by: 
Peter Orchard

An uncommon species found mainly, but not exclusively, on chalk and limestone grassland from May right through until mid-September.



  • Brown Argus: the brown blue.

    Post date: Wednesday, 27 May, 2015 - 00:00

    The brown argus (Aricia agestis) is far from common and was, for many years, thought to be in decline because of its dependence on chalk and limestone grassland. However, more recently, it seems to have adapted to other habitats and so now appears to be seen a little more and in more varied places.

    Despite being brown it is a member of the blues! The females of many blue butterflies are brown but the brown argus is quite a small butterfly; both sexes have a deep brown colouring to the wings and has very clearly defined orange dots that go along the complete edges of the wings. Not easy to identify in flight, you need to see it at rest or feeding to be sure.

    The species has two broods a year which seem to overlap and so you can find brown argus from May right through until mid-September.


  • Brown Argus in Dorset: what your tweets tell us ...

    Post date: Thursday, 25 April, 2019 - 21:33

    The brown argus is another blue butterfly that is not blue; it is a member of the family hesperiidae. The problem with the brown argus is that it is very like the females of some other blue butterflies, especially the female common blue with which it shares habitat preferences and so it may be either under recorded or even over recorded through misidentification. It is, however, a much more consistent brown colour (if that makes sense) and the dots along the wing are very distinct orange rather than also part silver and black. That is very well if the butterfly is stationary bit what if it is in flight? In flight the underwing of the brown argus is silvery grey whereas the common blue has a darker, more blue underwing. Easy ...? The brown argus has a preference for common rock-rose as its larval food plant and rock-rose is a plant of chalk and limestone grassland so if there is no rock-rose then think 'common blue'.

    The books suggest there are two broods of brown argus which means they can be seen from early May until late September but with a lull at the end of June/beginning of July. In the Nature of Dorset tweets database there are twenty five records showing their first emergence in week 17 which is last week April/first week May and then reports weekly until week 22 in Mid-June. Reports there after are much more intermittent until week 35 in September but there are notably records for weeks 41 to 43, well into October. That could be an indication of a third brood here in the south or maybe it just means the second brood survive longer if the weather remains favourable?

    There are records from twenty four sites and they are almost exclusively sites on chalk or limestone with Ballard Down near Swanage seemingly good for them. Surprisingly, perhaps, there are no reports from Portland (yet). 


Common Name Brown Argus
Scientific Name Aricia agestis
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