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We have a puzzling event of an adult Holly blue found in mid January in Edinburgh. An ivy hedge was being cut and the butterfly was found crawling on the cuttings.

This species overwinters as a pupa not an adult, so something unusual has happened. My first assumption was that a pupa must have been artificially warmed up, triggering an emergence. However further investigation doesn't indicate any likely source of warmth.

So the other options seem to be that emergence was triggered as a result of disturbance or that it overwintered as an adult (a third generation one emerging into unsuitable weather then sitting tight for the winter?).

Neither of these option seems at all likely though? Butterflies aren't normally triggered into emergence by disturbance, especially at short notice as they take some time to gear up for emergence? Holly blues have never been recorded overwintering as adults?

I'm stumped so any insights would be welcome.

I don't think it could have completed its natural pupation phase this early given it is not in an artificially heated environment (and certainly not as a result of disturbance), unless somehow it turned into a rather belated additional brood specimen, many of which have been regularly seen in southern England during the month of November.

My only experience with this was a Speckled Wood reported to me around Christmas a few years back. It was found in a garden centre and the lady took it indoors. Again, this species pupates in the pupal stage (also larval stage) so whatever alchemy dictates whether it becomes a hibernator or completes its cycle before year-end may be a factor.

Certainly, at that latitude it is extremely surprising, but butterflies have a habit of doing surprising things.