Friday, July 17, 2009
Apatura iris 'cretaceus' - Emperor Also A Species Of Downland Crests!
We can now add 'downland crests' as a further habitat association of the Purple One! Following on from sightings over several years, by Biddy and Paul Dimmer (guardians of the stunningly beautiful Graffham Down Reserve - see right), Bruce Middleton (Murray Downland Trust and South Downs Joint Committee) and myself, further effort has been focussed on studying these 'most irregular' colonies.
On 4 July I watched two males clashing above the downland crest near Storrington, at an elevation of 558' above mean sea level. These are not just 'hill-topping' males - the butterfly breeds here. Prior to the demise of the 'Magic Sallow' (foully killed by tree-rats), I have previously watched females lay eggs, and have monitored larval and pupal development on the site since 2006. The surrounding lowland is arable, so there are no woods from which the butterfly is ascending.
On 13 July, following reports from the Dimmers, I visited the crest of Graffham Down near Midhurst, with Hannah Sanders and Susie Milbank. A total of four 'apparent' males were observed, together with an egg-laying female at an altitude of 728' amsl. Although the butterflies may well ascend from the wooded slopes and lower areas of Charlton Forest to the south, they clearly live and breed here, in this most lofty of habitats. I have since seen a photograph of an egg-laying female taken by Paul Dimmer two days previously. The image to the left shows the margin of the main stand of nursery sallows (near left), and a male assembly area in the pines (far right).
The image to the right shows a male 'on station' near the top of one of these pines, about 40' above the very highest point of the downs here (c.760' amsl!).
We walked west along the South Downs Way and came across another male iris, just short of the triangulation point at Heyshott. He was crossing an open meadow on the very peak of the downs at an elevation of 745' amsl, travelling from one stand of ash to another.
Back towards Storrington, male Emperors have been recorded sitting on the chalk path of the SDW above Rackham village, at an altitude of 623' amsl.
We clearly still have much to learn about this butterfly - and long may that be the case!