The monarch butterfly spends about two weeks as a chrysalis. The day before it ecloses, or emerges, the bright colors of its wings become visible. But how will the butterfly get out? Look carefully at this close-up view. Do you see any clues?
Monarch scientist Dr. Karen Oberhauser describes the process: "To emerge, the adult monarch must split open the pupa cuticle along a line of weakness." You can see one of the zipper-like lines of weakness in the image.
"First, it swallows air through the pupal spiracles," says Dr. Oberhauser. The spiracles look like tiny holes. They allow the monarch to obtain oxygen during development.
"If you look closely at an adult ready to eclose, you'll see there's air between the pupal shell and the adult cuticle. This air traveled through the adult's body, to spiracles on the adult thorax, then out these spiracles to the space between the shell and cuticle."
"The adult then swallows some of this air into its digestive system. The air causes the body of the monarch to expand. Finally, the cuticle splits along the line of weakness and the adult pulls itself out."
"It's very hard to predict when a monarch butterfly will come out of the chrysalis," says Dr. Lincoln Brower, "although most monarchs are thought to emerge in the morning hours." The chrysalis on the right is closer to eclosing than the one on the left. Study the shapes carefully and see if you can find a difference. (The color differences you see are only due to light.)
Did you notice that the chrysalis on the right has stretched like an accordion above the gold band? This is a clue that emergence is getting closer. While it may still take several hours, the monarch won't eclose before this change has occurred.
Enjoy! Find a chrysalis, wait patiently, and you may witness this miracle yourself. Meanwhile, enjoy this photo gallery and video clip.