The Marble White colony here as at Brockadale is  an introduction carried out in  the late 1980s.

  Marbled Whites have since colonised areas close by 

Yorkshire Marble Whites
19th July 2002 Anston, Little Stones. The most curious aspect of the entire day was the marked difference in the behaviour of the Marbled White in Little Stones and those  deeper in the wood some half a mile away .Though the sun around  3.15 pm managed to come out from behind  the clouds, the butterflies rather than take to the air took up roosting positions only opening their wings for a brief second. However at Little Stones a short while later around 4pm they were still flying and occasionally nectaring on the Knapweed - a favourite - Scabious and even Thyme.

Each habitat was obviously  different in subtle ways sufficient to modify behaviour. What these differences were was anybody's guess and it vividly demonstrated how complex habitats are and  not reproducible at will. Tried out the field camera. I disturbed a Marbled White resting on grass close to  the invading Bracken and Dog's Mercury. This was hardly typical habitat as I have never seen a Marbled White resting on Bracken.
20th July 2002 Little Stones. Despite the general overcast day I managed to get some photos during the brief intervals of sunshine. One was a somatic variation of a Marbled White with a slight smudging of melanin on one of the underside hindwings. 
Marble White
Above. June 27 2000 Brockadale West Yorks.  Around 4pm and on the point of leaving I believe I discovered how the Marbled White fans out from Brockadale. Rather than move up the valley bottom amongst the dense grass, parsley, pignut toward Wentbridge they are actually drawn by the immense fields of barley, flying some 30yards into the barley and even settling before returning to their more usual habitat. I chased one in a parallel dance for some 100yds clicking the shutter repeatedly though my running alongside it may have prevented the butterfly from returning to the reservation. Thinking I was pursuing the butterfly I was in fact causing it to panic as it tried to get away from me. So maybe it was behaving in an unaccustomed manner. A south westerly would propel them toward Eggborough and Drax not toward Ferrybridge. Maybe a shift in wind direction from the south east (which is unusual) blows them towards Leeds. (note the underside  of the ab: citrona in the top left photo)   Above: Marble White on a very dark day in late June 2000.