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Aricia agestis
This is a relatively uncommon butterfly as the principal larval food plant is Common Rock-rose, and this wildflower is only found naturally on chalk downland. Away from the South Downs, this species lays its eggs on a variety of wild Geraniums such as Cut-leaved Cranesbill. Most colonies are very localised and usually quite small, but they can be huge, as at High and Over, in 2023, when Bob Eade found 3,000+ in just a few acres of chalk grassland.
This is a diminutive butterfly, and it can be easily over-looked. In flight, the silvery flash of the wings is distinctive (and it can be confused with a Small Blue), and when perched, it is not always easy to separate from a “mostly-brown”, female Common Blue. A good ID feature for Brown Argus is the ”figure-of-eight” which is located mid-way on the upper edge of the hindwing.
The first adults usually emerge in the first half of May and fly until late June. The second brood flies between early/mid-July to mid-September. If we experience a warm spring and we are blessed with a fine summer, there may be time for a weak third-brood, which occurs between late September and late October.
Anywhere, where there is Common Rock-rose on the South Downs. Reliable sites include Chantry Hill at TQ085123, High and Over at TQ509013, Levin Down at SU887130 and Steyning Downland Scheme at TQ168112.
Female Brown Argus nectaring on Birdsfoot Trefoil – photo by Martin Kalaher
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Territorial male
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Territorial male
Male nectaring on Meadow Buttercup
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Nectaring on Marjoram
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A side-view with the "figure of eight" which is located mid-way on the upper edge of the hindwing
Butterfly Conservation Brown Argus
