Monarch Caterpillar to Chrysalis II

AKA the sixth moult

In my last series of “Monarch caterpillar transforming to chrysalis” time lapse photographs, the 30-minute time interval missed the moult. For this series, I set the Canon EOS 5D Mark IV to remote from a IPhone 7, tethering me to hanging around the house for an afternoon of waiting for the magic moment of “transformation” (more accurately called “the moult”), thinking through the nature of the moment.

A monarch caterpillar accomplishes seven body transformations shielded from view. Six within its skin: the first five retaining a caterpillar body configuration, the sixth transforming to chrysalis. For all six, an enveloping skin conceals the change. The same holds true for the seventh transformation. The chrysalis remains opaque green with bright gold spots until turning transparent after the transfiguration to butterfly is complete.

The sixth transformation happens when the fifth instar caterpillar, fully sated with milkweed, climbs to a perch, spins silk around a set of prolegs, affixing them from a horizontal surface from which to hang. For this set I captured the moult of two monarchs hanging side by side inside a mesh cage with an east facing window for light. Even though the day was sunny, with the f-stop set to the lens maximum (32) for the deepest field of view, ISO at 32,000 the energetic skin shedding movements of the chrysalis cause blurring.

For 10-12 hours of profound bodily configuration changes the hanging caterpillar hangs without movement. In the last image of this first set, the next caterpillar is blurred by initial moult movement.

My attempt to capture a video of the moult was frustrated by inadequate lighting, the result was too dark to use. I must solve this technical challenge as the motions of the chrysalis as difficult to believe without visual proof. That said, here is the second moult with the first completed moult in background.

An interesting fact is the caterpillar uses silk to attach the skin to a substrate for the first five moults to hold the skin back while it crawls out of the discarded skin. The first meal of the hatched caterpillar (first instar) is the egg, the shed skin is the first meal for instars 2 – 4. The shed skin of instar 5 drops from the chrysalis. This is why you should never remove a Monarch caterpillar from the leaf, as in doing so may hinder a moult in progress.

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