Polyommatus coridon
This is a fairly common blue butterfly of flower-rich, chalk downland. Male Chalk Hill Blues have very pale blue uppersides with a wide brown border and are relatively easy to identify. Female Chalk Hill Blues can be a lot trickier to identify “in the field” as they are very similar to female Adonis Blues. The females of both species are chocolate-brown, and both have a distinctive chequered border. If these two species are flying together in late summer, then a high-quality photograph and a good ID book is required to distinguish between them.
There is one emergence, which begins in early July and lasts well into September. Chalk Hill Blues live in discrete isolated colonies, but occasionally a male may wander far-and-wide and be seen a very long way from the nearest breeding site. If Horseshoe Vetch is abundant and lush, then some colonies of Chalk Hill Blue may number in the hundreds of thousands. Truly an astonishing sight.
Locations to see Chalk Hill Blues, include: Birling Gap at TV562957, Chantry Hill at TQ085123, Friston Forest Gallops at TV553997, Medley Bottom (Amberley) at TQ044116 and Windover Hill at TQ537034 (Ewe Dean) and TQ543030 (Deep Dean).
Male Chalk Hill Blue at rest – photo by Dave Brown
Female with open wings – photo by Dave Brown
Female with closed wings – photo by Dave Brown
A “tatty” female – photo by Dave Brown
Male with open wings – photo by John Williams
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Male nectaring on Birdsfoot Trefoil – photo by Martin Kalaher
Butterfly Conservation Chalk Hill Blue
