Generation after generation the monarch butterfly lay eggs which makes a caterpillar that grows up to be a butterfly. When a Mother butterfly lays her eggs, it takes a few days then the caterpillar hatches out.
For a caterpillar to grow up, it eats milkweed leaves from the swan plant. A caterpillar eats milkweed for 2 reasons; 1 is that a caterpillar has enough energy to turn into a butterfly. The second reason is so when the bird comes to eats the adult butterfly is spits it out because of the poisonous milkweed.
After the caterpillar is full it goes to a tree nearby and hangs up side down and turns into a chrysalis. As it hangs up side down it waits for about 2 and a half weeks until the chrysalis turns black. After 2 weeks it hatches out of the chrysalis and a butterfly pops out with two massive wings.