Monarch caterpillars molt (shed their skin) five times throughout their larval stage. The "skin" that is left behind is actually the caterpillar's exoskeleton. An insect's skeleton is on the outside, as opposed to on the instead like mammals, fish, reptiles, amphibians and birds. Endoskeletons provide support inside the body in the form of bones and cartilage, whereas As caterpillars grow, their exoskeleton gets too tight, so they need to shed it in order to continue to grow. Each molt results in a new "instar" stage. Therefore, when the egg hatches, that tiny 2 mm caterpillar is in its first instar stage.
It will molt three more times and grow exponentially over a couple of weeks. Each stage lasts 3-5 days. The fifth and final molt is when the fifth instar caterpillar becomes a chrysalis.
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North American Milkweed Species Identification
The following slides and associated plant profiles are part of an ongoing project to create a comprehensive North American Milkweed Field Guide. The guide below is incomplete, but should be finished by fall of 2024.
Please Note: None of these slides or profiles are to be used or reproduced in any way for commercial purposes. They are for education only and shall not be printed or distributed.
