Sorry Jonathan, I can't help either, but I am amazed that they can even be found in such a cold place, 3/4 of it lies in the Arctic circle
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In Qaqortoq in South Greenland the winter is mild with as the coldest average temperature of -5.5° C, whilst the temperature remains above freezing from May to October. In Kangerlussuaq in the Arctic Circle, during winter the average temp is as low as -22° C, -strangely enough though - during the summer it is the warmest place in Greenland with mean temperatures of around +11° C in July!
I hope someone can help with the info you need, and if ever get anty photo's of these butterflies we'd love to see them - good luck!