I am going to in my most uneducated way to give you a peek at the cycle of the Monarch Butterfly Life. There are some questions that we love to have answer's to and that will be on the "Most Asked Monarch Questions"
The butterfly has a life cycle of 6 to 8 weeks that is it goes from a egg, to a caterpillar to a chrysalis (pupa) to a butterfly. The egg takes about 4 days to mature and it is so tiny you might miss it .
Once it has started it's life it begin the task of eating all the milkweed you can possibly have. These little devils eat the milkweed down to bare twigs. It will eat for approximately 2 weeks.
Think about how much we eat in two weeks. Plant a lot of milkweed. Once the caterpillar is full it now makes itself into chrysalis
Here is a post with great pictures of this cycle.