I think worms are fun. Fun to look for and dig up. Fun to hold, and fun to save after a rainy day. Plus my boys love to do all these too. This is why an activity with "worms" is a must do for me.
I did not use a particular worm book, but I do love the Diary of Worm book. It is really a diary of a worm and his friends/family. They are really cute, but are more of a preschooler book. I made today about silly animals and read the book Bark, George. I know, nothing to do with worms; my friends didn't seem to mind.
You will need brown paint, white construction paper, and cooked spaghetti.
I tried this a couple ways and the best result is place the spaghetti down on the paper and then pour the brown paint over the spaghetti. I learned that many of my friends did not want to touch the spaghetti without the paint because it was too sticky. I am sure if you use freshly cooked spaghetti this would not be too much of a problem. Mine was in the fridge over night.
Let your child move the spaghetti with their hands and talk about how it feels. If you find that they do not want to touch the spaghetti offer them a tool. I used toothbrushes. The ones that would not touch it, loved it once I gave them a tooth brush.
The end result is what looks like worm tracks on your paint.
Have you used spaghetti before in your art?