Aricia agestis favours open, chalk and limestone grasslands, but can also be spotted on coastal dunes, in woodland clearings and along unused railways.
   They are found in dry, sunny and open habitats, including heathland and downland, and they seem to be expanding their range as the climate warms up.
   They are a small butterfly that is on the wing throughout the summer, between May and September.  
   Unlike most other "blues", they have no blue scales on the dorsal side, both sexes being primarily brown in color as the name suggests, although these butterfly do have a blue sheen when seen at certain angles to the light. Both sexes have beautiful orange spots on the dorsal side of both forewings and hindwings.
   The Brown argus has bronze / brown dorsal wings with an orange band of spots across the edge of each wing. They are quite similar to female Common Blues, but they tend to be smaller.
   Males of the first brood begin to emerge in early May, with females emerging about a week later.
   They have a potential lifespan of about 2 weeks, but on average most live for less than a week. The emergence is protracted, and the 2 broods often overlap at sites where populations are large.
   Males tend to congregate in sheltered areas along dykes or at the bottom of southern facing hills. They do not have fixed territories, but perch in various positions on grasses and flowers, and fly up instantly to investigate every passing insect.
   Not being the most intelligent of butterflies, they seem unable to differentiate visually between flies, Skippers, Blues and Fritillaries.
   Adults of both sexes nectar at a variety of low growing flowers, the first brood favoring Daisy, Buttercup, Bird's Foot Trefoil, Horseshoe Vetch, Common Vetch, Milkwort, dDandelion and Rockrose. Summer brood adults tend to congregate for nectaring at clumps of Marjoram at the bottoms of hills.
   In the afternoon they roost communally on grass heads, usually with the males and females in separate groups.
   The roosting sites are usually on the top of banks, where the adults are exposed to the last rays of the setting sun.