Friday, June 30, 2006

Brown argus, Aricia agestis, in Hastings

I recently saw a brown argus butterfly in another visit to the Marline Valley meadows, an SSSI on the western outskirts of Hastings. These butterflies are markedly smaller than the common blues that they fly alongside and the males as well as the females are brown.

Although quite common in places on the chalk, this butterfly seems to be rarely seen elsewhere in Sussex and, where it does occur, it is usually on, or near, the coast. The main foodplant of the caterpillars is rock-rose, Helianthemum chamaecistus, but this does not occur in Sussex away from the chalk, so the Marline larvae are probably eating the alternatives of stork's-bill or dove's-foot cranesbill.

The butterfly was recorded from Marline Meadows in 1989 and it is good to know that a colony is still there. As Jeremy Thomas says in his Butterflies of Britain & Ireland populations away from chalk, limestone or dunes are "invariably small and very rare."

The first generation adults are probably over by now, but there should be a larger second generation from late July to early September.

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