First of all, eggs are produced by the moth and it takes ten days for each egg to become a silkworm larva that feeds on mulberry leaves.

• 第一句话简单明快，点名了有四个过程（其实在写作过程中说明了五个过程），为第一个图的中心句，下面只需要把四个过程说清楚就行了。