Northern Brown Argus

The Northern Brown Argus (Aricia artaxerxes) is a rare, small (2-3cm) chocolate-brown butterfly found in Scotland, typically featuring a distinctive white spot in the center of its forewings. It is a glacial relict species, restricted to northern landscapes following the last Ice Age, and thrives in sheltered, flowery grasslands and rocky coastal areas, often where common rock-rose grows. 

Here are interesting facts about the Northern Brown Argus in Scotland:

• Ice Age Relict: This species is a survivor from the last Ice Age, 12,000 years ago, that stayed in northern Britain as the climate warmed.

• Exclusive Food Source: The caterpillars feed only on Common Rock-rose (Helianthemum nummularium), restricting the butterfly to areas where this plant grows, often on south-facing limestone slopes.

• Distinctive Scottish Subspecies: The Scottish subspecies, artaxerxes, almost always has a prominent white spot on its forewing. In contrast, those in northern England often have dark or faint spots.

• Homebody Butterflies: They are incredibly sedentary, rarely moving far from where they hatch. This means they live in small, isolated colonies, often with fewer than 50 individuals.

• Arthur’s Seat Disappearance: They once lived on Edinburgh’s Arthur’s Seat but disappeared by 1869 due to over-collecting. They were successfully rediscovered in the Holyrood area in 2005.

• Communal Roosting: They have a fascinating habit of roosting together at night or in poor weather.

• Surprising Resilience: Despite severe habitat loss (a 39% decline in distribution between 2010 and 2019), they have shown resilience against disasters, such as surviving massive grass fires that previously destroyed their habitat.

• Conservation Status: The species is listed as Vulnerable on the 2010 IUCN Red List and is a key target for conservation in Scotland.