I agree this Wiscoonsin winter was harsh. Our family overwintered ten Black swallowtails (also in an unheated garage in a mesh cage to keep rodents out) and they all hatched this spring thanks to the overwintering techniques learned from this forum. Thank You to all who posted links and info. last fall. It is so great to see the miracle of a butterfly hatching!
We have one Giant swallowtail that never hatched. When does one give up hope? We found him as a full-grown caterpillar whereas the Black swallowtails were found having just hatched from eggs on our dill. The swallowtails were a blessings since we had zero monarchs last year. Anyway, we've only seen two monarchs this year, no eggs on our milkweed.