From Caterpillar to Chrysalis
Contributed by Dr. Lincoln Brower

Why does the monarch twist and turn so vigorously as the chrysalis forms?

Dr. Brower explains...

Listen to Dr. Brower

This is a really critical stage in the life history of the monarch because this is truly when the caterpillar has just become a chrysalid and it has just shed its skin. There are two things that are happening when it twists:

1) Look at that little black post at the top under a microscope you'd see dozens of beautiful little hooks. As the chrysalid twists, this black post with barbed hooks are getting into the silk. If that little post doesn't get into the silk then the chrysalid will fall to the ground. And if it falls to the ground it will kill the chrysalid because at this stage the chrysalid is incredibly delicate and--it's really just almost a bag of fluid.

2) The second thing that is happening is that — if you watch (the video clip) really carefully — you'll see the larval skin — which now looks almost like a fly that slid up and up and up and up. The chrysalid has to get rid of that because if it doesn't it will stick to the surface and that will deform the butterfly. The butterfly would not be able to get out of its chrysalid unless it gets rid of its skin which messes up the metamorphosis process.

The caterpillar spins a silk pad. When it transforms into a chrysalis, barbed hooks hold strands of the silk so the chrysalid won't fall to the ground.
Scanning electromicrograph showing the tip of the cremaster post of a monarch butterfly chrysalid embedded in the silk pad.
Images © Dr. Lincoln Brower, Sweet Briar College. All Rights Reserved.

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