Monarch II - The Caterpillar Awakens

Here's the second Monarch Butterfly I got a picture in 2020, spotted about a half hour after the first. Yesterday I talked mostly about what Monarchs eat; today I'm going to go over their complicated life cycle.

All Monarchs begin life as an egg. Their mother will lay an egg on a milkweed plant. I think they usually lay a single egg on the underside of a milkweed leaf. This probably helps protect the egg from rain, and maybe excessive sunlight. This probably also helps hide the egg from predators and parasites. (Though Monarchs eventually become poisonous through eating the poisonous milkweed, the egg hasn't eaten anything yet.) The mother Monarch can lay anywhere from 300-1100 eggs all told, though she lays her eggs one at a time and almost certainly avoids laying multiple eggs on the same leaf to prevent her kids from competing against each other.

After hanging out on the leaf for 3-8 days, the egg hatches and a very small translucent green caterpillar emerges and begins eating. This is its first instar, basically a phase of caterpillar development. After eating and growing for 3-5 days, the caterpillar outgrows its original exoskeleton and molts. After molting, the caterpillar is now in its second instar, and it's both bigger and has the stripes we associate with Monarch caterpillars. Monarchs go through 5 instars in all, and feasting on milkweed between its molts. It's said that the life of a caterpillar is all about eating and pooping; caterpillar poop is called frass.

At the end of the 5th instar, the Monarch is now ready to begin the transition from caterpillar to adult butterfly. To accomplish such an extreme change to its body, the caterpillar finds a good place from which to hang (it doesn't have to be a milkweed plant) and creates a silk pad on the underside of a surface. The caterpillar hangs upside down from the pad with the front of the caterpillar curling up a bit to form a "J" shape. After doing this for the better part of a day, the caterpillar straightens itself out, sheds its exoskeleton one last time, and enters it's chrysalis phase. (Cocoons are more of a moth thing.)

The chrysalis starts out as an opaque lime green with a little golden line and a couple gold spots. This is where the magic happens, radically rearranging and transforming body parts from caterpillar to butterfly. The transformation takes 11-12 days plus or minus 3 days. Towards the end, the chrysalis becomes translucent, and you will be able to see the orange-and-black coloring that the adult butterfly will have.

Once the Monarch emerges from the chrysalis, it hangs there for a while as its wings expand, dry, and stiffen. At that point we should have a fully functional adult Monarch butterfly, ready to fly off. Its life of eating and pooping are over; its life of drinking (nectar), breeding, and (if female) laying eggs has just begun.



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