The key species are coming in thick and fast now. When I read that Marsh Fritillary were flying at my site of choice there was only one place to go on this warm and sunny day. In my home area of Oxon, Bucks and Berks there is just one tiny and fragile cluster left. Not too far away in Wiltshire variable concentrations of the species can be found, and Cotley Hill (ST917427) near Warminster must take the title of Marsh Frit grand central. My visits here in 2011 and 2013 yielded large numbers of what is a declining and distinctly localised butterfly nationally, and today was a repeat experience.
From a lay-by at a roundabout on the A36 near Heytesbury, a footpath leads uphill into a long south-west facing slope covered by unimproved grassland. This site supports a rich flora and 29 breeding species of butterfly. Taking the first sheep track left at the foot of the hill I quickly began to see Marsh Fritillary, as on those previous visits. An observer walking back told me there were hundreds on the hillside above and indeed there were. This butterfly has a pleasing habit of sitting up and keeping still for the camera, and one after another did just that as I walked around.
Marsh Frit can be very variable, the smallest males being a fraction of the size of the largest females. Although the chequered pattern is constant the wing colours can also vary a lot. Underwing shots are more difficult to come by. This newly emerged female (below) was still drying in the sun while already rejecting the attentions of a male suitor.
The supporting cast here was a check list of April and early May key species: Dingy and Grizzled Skipper, Green Hairstreak, Brown Argus, Small Heath and my year’s first Small Blue.
There was still time for a bonus butterfly so I walked up the main path and back to look for Wall Brown, having seen them here previously and at other Wiltshire sites. This species is virtually extinct in my home area. Back at the lay-by a Wilts man gave me directions to another location where he said they fly. About ¾ mile west of Avebury on the A4 is a lay-by on the south side of the road from where a footpath leads uphill through a Beech copse. On the eastern side of this, above some racing gallops is a worked out chalk pit with an exposed chalk bank. And here indeed I encountered this rather splendid Wall Brown (below).