The only butterfly who wasn't ready to go was Bulldozer, who made his chrysalis about 2 weeks after the others, and therefore hadn't hatched yet. But I was concerned that the other butterflies would suffer, stuck in our (small) bug house almost two weeks after becoming butterflies and trying to fly. So we compromised by letting the butterflies go, but attaching Bulldozer's chrysalis to the underside of our deck, so he can fly away whenever he hatches.
Only one butterfly died this year, and we don't know who it was: several butterflies hatched the same day, and one began languishing almost immediately. Sweet Pea insists it can't be hers, because hers died last year. And Little Man and CC didn't seem to mind, because there were still plenty left.
Then Sweet Pea dropped her balloon, which landed on the grass and BANG! There were many tears shed. But we distracted her by showing her that the butterflies hadn't gone far -- as usual, they fluttered around a bit and then landed nearby for little breaks. I like to think they're "getting their wings."
Farewell, Morrison butterflies of 2018!