"Show and Tell" class- My Silk Worm Story

每天有个同学需要到前面讲一点关于科学和数学的东西，上个周五（13Jul12）我的Show and Tell

Good morning, teachers and friends.

Last month, I had forty two silk worms.  Today, I would like to show you the cocoon and eggs of my silk worms.  I don’t know if you have seen silk worms before, but China people keep silk worms as pets a long time ago.  The silk from the cocoons can be taken out to make clothes.  The cocoons come in many different colours.  My silk worms make cocoons of yellow and white.  There are also pink, blue and stuff like that.  The eggs of the silk worms also come in different colours.  I’ve got all of them with me – yellow, brown, and black. 

The life cycle of the silk worm is quite similar to the one of the butterfly.  First, a tiny silk worm comes out of the egg, and starts to eat fresh mulberry leaves.  It also molts several times, and changes colour as it grows.  The new born worm is black, then it turns yellow, and finally it becomes white.  Then it eats more mulberry leaves and gets fatter, storing silk in its body.  After three to four weeks, it spins into a cocoon and waits to change into a pupa, then a moth.  After two more weeks, a moth craws out from this hole of the cocoon.  Then the female moth lays eggs on paper, just like this one.  After laying eggs, the moth soon dies.  And the life cycle starts again.  I’ve also taken pictures of the silk worms and moths, maybe I can show you next time. 

Thank you very much.