Caterpillars on the move!

Today there was great excitement when we arrived at school!  On the back wall we noticed a green blob hanging off the vibrant red paper!  One of our caterpillars had turned into a chrysalis and conveniently made it's new home on the wall until it turns into a monarch!  We are wondering how long it will be until the chrysalis turns black and changes into a butterfly?  How do the beautiful gold spots appear?  What was the caterpillar thinking when he decided this would be a place to make the chrysalis?  We will watch with great excitement for the next change in the life cycle!