I'm in southern Australia. In previous years butterflies have arrived in late Feb, laid furiously, then the caterpillars start dying in mid-April when the frosts begin.
This year they arrived in mid January, it's now mid June, pretty cold (!5-18C) with frequent light frosts. But the caterpillars are still around! I've been bringing the last instar ones in under cover to pupate (which they don't always do well - take too long and often fall off) and I am even finding tiny ones. One today, a few days old, in cold, wintry conditions, chomping away on a leaf. They seem fine.
Every day I find butterflies which can't fly because it is too cold so I bring them in too. One has survived for two months, though the rest won't self-feed.
This is just not possible! Are they adapting to cold conditions or what? There are no native butterflies around now and very little is flowering. So it isn't a good survival strategy, but I'm hoping I can keep a few going until the weather warms up to repopulate.
I never imagined this could happen. The seasons have been a bit warmer but much drier. Though winter is certainly upon us now!