but they have until dawn to complete their transformation. 直到黎明它们才完全转化完毕

163. The biggest insect emergence on the planet is underway.
     地球上最大规模的昆虫羽化就要开始了
164. They invade the upper branches, where they climb out of their external skeletons and assume their adult winged form.
     占据上端的树枝后 若虫开始进行转变到蝉的蜕皮动作
165. At first they're white and soft,
     一开始它们又白又软
166. but they have until dawn to complete their transformation.
     直到黎明它们才完全转化完毕
167. After an absence of seventeen years, the forest is now overrun by cicadas.
     在17年的缺席之后 森林中的蝉泛滥成灾
168. The adults are clumsy and very edible.
     成年蝉不仅笨拙而且非常美味
169. For turtles and other inhabitants of the forest this is a feast they're lucky to see once in their lifetime and they gorge themselves while they can.
     对于龟和其他森林居民来说, 可能再也没有运气能这样狼吞虎咽,大快朵颐

来自《行星地球 第一季 第十集 Planet Earth S01E10 季节森林》第 166 行