Queen Of Spain fritillary (Issoria lathonia)

[Nigel-V]

I would be grateful for any info on overwintering this species. My
information suggests this has permanent populations as far north as 63N. I
find this hard to believe as my lava seem to refuse to hibernate. I have
them outside in a greenhouse (Unheated) at temps down to 0C and they still
seem content to stay up on the foodplant!
Any info on range is also welcome.
Thanks
Nigel V