We frequently find hibernating butterflies in folds of curtains etc. keep the room cool so that it doesn't come out of hibernation would be my suggestion and, come spring perhaps leave a little honey or sugar water for it.

and put an "Exit ---->" sign up!

:^)

Which won't work!

When you find it flapping desperately against the window in spring, open it! If the butterfly is too silly to find the opening, catch it against the window with a drinking glass and a piece of card and let it go outside.

Thanks guys. Have told my boys to leave well alone and hope butterfly will stay there till spring.

With respect, it won't be a monarch. Most likely to be a peacock or red admiral. Smaller, and it'll be small tortoiseshell. Monarch's are American, and I grew up in New Zealand with them, too.

New Zealand is in America?

;^)

http://www.monarch-butterfly.com/monarch-news.html has interesting facts about the four generations of Monarch butterflies throughout the year.

There wouldn't be Monarchs in New Zealand, either, though they may have a look-alike species, too. Monarchs occasionally get blown to the British Isles on storm systems crossing the Atlantic, but they normally can't reproduce--not enough of their favorite milkweeds.