Niles-Maine District Library


Mission Accomplished Part 1: The Molting of the Monarch

The caterpillar house in KidSpace is a busy place. Inside, the caterpillars eat, grow, poop, molt, and sleep. They even fight over territory every once in a while. Outside, kids and their grownups observe, discuss, record, draw, and photograph every move these little critters make.

The monarch life cycle is a remarkable four-stage process that takes approximately 30 days. Like all butterflies and moths, monarchs undergo a complete metamorphosis in which there are four distinct stages: egg, larva (caterpillar), pupa, and adult butterfly.  In this post, I will describe the stages leading up to the chrysalis. I will leave final stages for another day.

Adult female monarchs lay one egg on the underside of a milkweed leaf and then move on to a new leaf to lay another egg. The egg stays on the leaf for 3-4 days before it hatches. When the caterpillar is born, its first order of business is to eat the eggshell, which is full of vital nutrients that help the caterpillar grow. Then it eats the leaf on which it was born, and moves on to a new leaf, and so on and so on.

As the caterpillar grows, it gets too big for its skin. When the skin gets too tight, the caterpillar molts (this is a fancy word for shedding its skin). Caterpillars molt five times during the larval stage. The final molting results in a beautiful green-flecked-with-gold chrysalis.

This is one of the most exciting events to witness at the butterfly house. Everyone hopes to catch the final molting, but few have the patience or free time to wait. First the caterpillar finds a place to attach itself and hangs upside down and curves its body into the shape of the letter j. It hangs in that shape for 8-12 hours, as the antennae dry up. When the molting starts, it happens very suddenly, and only lasts about 4-5 minutes. I have been trying to capture this on video many times. Yesterday, I finally succeeded! So without further ado, witness the amazing transformation:

Stay tuned for a future post in which I will attempt capture a butterfly emerging from its chrysalis. Wish me luck!

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