Where to see
Habitat: This butterfly used to be only on warm south-facing chalk downs but in the 1990s it expanded into more ordinary grasslands on clay, into woodland clearings, verges and even heaths.
Caterpillar foodplants: Rock Rose, Common Storksbill, Dove's-foot Cranesbill, Cut-leaved Cranesbills
Best places: Fontmell Down, Hod Hill, Ballard Down, Durlston CP East, Durlston CP West, Townsend Quarry, Cerne Abbas, Avon Heath CP North, Avon CP South, Badbury Rings, Stour Valley.
When to see
1st brood: End April - Beginning July, Peak: End May. 2nd brood: End July - End September, Peak: End August.
Sightings by month (last 5 years)*:
Sightings this year*:
To tell male from female, look at the upper forewings. The males’ orange spots fail to reach the wingtip, while the females’ orange spots go right up to the wing tips.
The male is also recognisable by its behaviour: for a small butterfly, it is amazingly aggressive. Looking slightly silvery in flight, it will attack any butterfly flying over its perching spot.
The most likely species with which the Brown Argus can be confused is the Common Blue, and to sort these out you ideally need to see the underwing.
It is also worth noting that if you are trying to differentiate between Brown Argus and Common Blue, if you are looking at a male Brown Argus, it will be attacking any other butterfly which nears its perching spot; if you are looking at a female Common Blue, she will be quite and cautious.
Compared to the female Brown Argus, the female Common Blue has more blue scales on the surfaces of the wings, and the orange dots on the upperside hind wing have black dots edged with white, while the Brown Argus has almost pure chocolate brown upper wings and the orange dots on the upper hind wings are edged by black dots and just a little white.
*Note: The charts shown on this page are drawn only from casual sightings submitted to this website. Records from this website will be added to a lot more data collected throughout the year and used to compile the five-yearly Butterfly Atlases for Dorset and the UK.