How many hours does it take for a monarch caterpillar to turn itself into a chrysalis?

Last year I decided to "raise" a few Monarchs. I was determined to watch them morph into their shiny green chrysalis. I had them in my daughters bug barn and went so far as to take them to work with me so I wouldn't miss the event. One morning I noticed one of the caterpillars doing this odd kind of shaking "dance". I had to go to lunch and left them on my desk until I returned. I returned 45 minutes later to see that it had completely morphed into its beautiful green shiny home. Since I had 2 more that hadn't changed yet, I didn't take my eyes off of them when I saw them do their "dance". I was fortunate enough to take in a beautiful transformation. It's something I think everyone should see, really! Watching it happen before your eyes and seeing how it loosens itself from its outer skin (that's what the dancing turned out to be) and transforms into the chrysalis is mind boggling. I hope you have the chance to catch it for yourself!