Monarch Caterpillars, Different Instars

• 19 Mar, 2008
• 2 likes

When a Monarch caterpillar eats, his body grows and grows until his skin is too tight for him, so he has to molt, or shed his skin. He already has new skin under the old. In the next 2-3 weeks he will have to shed his skin 5 times. With each molt he advances into a new instar. In this pic there are 3 different instars shown and the one in the center has just shed his skin. You can see the skin behind him. Caterpillars are very vulnerable during the molting process and should never be disturbed. It may take a day or two for this process.