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Brown Argus

Aricia agestis

Not yet photographed by the community

Small brown butterfly with orange spots; looks like a female blue.

Species Profile

Amber List; declining in northern parts of its range due to habitat loss and fragmentation, though stable in core southern populations.

Lifespan: 2–4 weeks as an adult butterfly; larvae develop over several weeks depending on temperature and food availability
Size & Weight: wingspan 28–34 mm
Habitat: Sunny, sheltered grassland and scrubland, particularly on chalk and limestone downland with abundant bird's-foot trefoil and other low-growing legumes.
UK Distribution: Resident in southern and central England, with populations concentrated in the Midlands, southern counties, and scattered locations northward; absent from much of Scotland, Wales, and northern England. Produces multiple generations per year with peak flight periods in spring and late summer.
Diet: Larvae feed exclusively on bird's-foot trefoil (Lotus corniculatus) and related legume species; adults feed on nectar from small flowers and occasionally on rotting fruit.
Predators: Small birds, particularly warblers and wrens; spiders; parasitoid wasps and flies attack larvae and pupae.
Mating Season: April to September (multiple broods)
Breeding: Females lay eggs singly on or near food plants; larvae develop through four instars; two to three broods per year in the UK, with some populations producing a fourth partial brood in warm years.
Behaviour: Males perch on grass stems or bare ground in sunny spots, flying up to intercept passing females; they are highly territorial and quick, darting fliers. Females are more cryptic and spend much time near food plants. Both sexes bask with wings open.

Did You Know?

•The Brown Argus is one of the few UK blue butterflies with no blue coloration on the male's wings, instead displaying warm brown uppersides with distinctive orange spots.
•It is the only Aricia species found in the UK and is closely related to southern European populations.
•Larvae can enter diapause (suspended development) to overwinter as pupae, allowing them to synchronise emergence with spring food plant growth.
•Males perform 'hilltopping' behaviour, gathering on elevated areas to locate mates.
•The species has shown a northward range expansion in recent decades, possibly linked to climate warming, though it remains absent from most of Scotland.

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