The Brown Argus butterfly (Aricia agestis) has been found in some new Bexley sites in recent weeks. It was identified at Braeburn Park. Between 2 and 4 individuals have been seen at Grasmere Road allotment site in the past fortnight. There was 1, possibly 2 in the small rectangle of grass and wildflowers between Gascoyne Drive and Thames Road, Crayford, on September 7th (which probably means it is on the adjacent Perry Street Farm), and two more at Thames Road Wetland later that afternoon, confirming a sighting last year that I had been unsure about at the time.
It is not clear whether there is a range expansion going on or the species has simply been overlooked in the past due to its similarity to the less blue variants of female Common Blues.
Brown Argus wing undersides, showing diagnostic ‘figure of 8’/’colon’ spots in the middle of the leading edge of the hindwing. (Photo: Purnendu Roy)
Brown Argus at Crossness, wings open. Black veination crossing the white border, and lack of white in the orange lunules help distinguish this species from female Common Blues. (Photo: Mike Robinson)
There is evidence that the species has widened its caterpillar diet, and that this has enabled a spread into new areas.
Chris Rose
