英语语法分析

When they reach full size, they attach to a leaf by their tail, and a pupa is formed.

当它们长到最大尺寸时，它们用尾部附着在树叶上，蛹就形成了。

During the pupa stage, they do not eat foods but do sit at the surface and breathe air through two small tubes.

在蛹阶段，它们不吃食物，但在水面游动时会靠两个细小的管道呼吸空气。

This stage (阶段) of a butterfly's life is known as the "pupa" stage.

蝴蝶生命中的这一阶段被称为“蛹”。