Birth of a Butterfly

At the end of summer last year I put a caterpillar in a box. I fed it until it got big, then it turned into a cocoon (繭). I wasn`t sure if it would survive (= not die) the winter, because it gets pretty cold in Japan, & I kept the cocoon outside, not inside my house. Finally the weather turned warm, & I noticed that a butterfly had emerged (=come out) from the cocoon. After its wings had dried, it flew away.

I was pleased (= happy) that the caterpillar finally managed to become a butterfly.

It`s a Common Yellow Swallowtail (Papilio machaon) (アゲハ蝶)

Grammar:
There are a few ways to say なります in English:
1. get + adjective形容詞 e.g. get big, get sick, get fat
2. become + adjective形容詞/noun名詞 e.g. become confused/become a mother
3. turn + adjective形容詞 e.g. turn 21 (years old), turn red
4. turn into + noun名詞 e.g. turn into a butterfly, turn into a typhoon
5. go + adjective形容詞 e.g. go crazy, go quiet