Northern Brown Argus

Description:

The Northern Brown Argus (Aricia artaxerxes) is a small, native chocolate-brown butterfly found in Scotland and Northern England.  On the wing from June to August, females lay eggs on the leaves of Common Rock-rose (Helianthemum nummularium). Adults can be found roosting head-down on grass or dead flower heads.

This butterfly is found on sheltered, flower-rich grassland where Common Rock-rose grows, including coastal and calcareous grassland. Sites also include quarries and old railway lines. The Scottish Borders is considered a stronghold area for this butterfly with colonies being found along the River Tweed, within the Pollinators Along the Tweed project area. It is also found on the County Durham coast and old quarry sites.

The Northern Brown Argus is a small brown butterfly with most individuals in Scotland having a characteristic white spot in the centre of each forewing. The underwings have a pattern of white, orange and black spots. There are two subspecies: artaxerxes found in Scotland, and salmacis found in northern England. The northern England subspecies typically has a black, rather than white, spot on the forewing.

Listed as ‘Vulnerable’ in the Red List of British butterflies this species has experienced a 39% decrease in distribution between 2010 – 2019. It is also a Scottish Biodiversity List species, considered to be of principal importance for biodiversity conservation in Scotland and in most urgent need of conservation action.

• Size: 25mm-31mm wingspan
• Life span: Annual life cycle; from egg to adult approximately a year
• Diet:  The Northern Brown Argus feeds on nectar from a variety of wildflowers.  Common Rock-rose (Helianthemum nummularium) is the sole foodplant for the caterpillar.
• Reproduction: The female Northern Brown Argus lays its eggs on the leaves of Common Rock-rose.  It is a single-brooded species
• When to see: Adults are active from June to August, with peak activity in late June and July.
• Population Trend:  Declining – Between 2010 and 2019, the Northern Brown Argus experienced a 39% decline in distribution (Red List of British Butterflies 2022).
• Threats:  Loss of habitat.  Scrub encroachment, overgrazing and afforestation (establishment of trees/forests in areas where there was previously no tree cover) in particular
• Fun Fact:  The Northern Brown Argus was once considered a subspecies of the Brown Argus (Aricia agestis).  The Northern England subspecies was first discovered at Castle Eden Dene in County Durham and is informally known as the ‘Castle Eden Argus’ or ‘Durham Argus’.

How you can help: 

Buglife is working to increase awareness of invertebrates and the Northern Brown Argus through specific projects, like our B-Lines project Pollinators Along the Tweed and campaigns, but we need your help!

Join a recording scheme and log your finds – send any records/sightings to Butterfly Conservation or download the iRecord app and get recording!

Do remember that we rely on donations to continue our work.  If you have searched, found and learnt about our incredible invertebrates on our website, please do consider Making a Donation, Becoming a Member or maybe even making a purchase in our shop.  For more ideas on how to support our work find out how to Get Involved.  Thank you 🕷

You might also be interested in

Small Pearl-bordered Fritillary

Boloria selene

Coastal Pearl

Mecyna asinalis