Since I had the great luck to be in the garden while a female Monarch laid its eggs on Milkweed plants, it made my job easier for tracking their development (see also Egg Stage page). Here are photos and videos below of freshly hatched Monarch caterpillars, and further below of the first few days. The first thing the tiny caterpillar does after hatching is eat its egg shell (or case) for its nutrients. It seems to take it several hours to do this.
The following video shows the tiny Monarch caterpillar starting to eat its empty shell:
Below is a video of a Monarch caterpillar starting to explore its surroundings after it ate its egg case:
THE FIRST FEW DAYS
Below are photos and videos of the first few days in the life of the Monarch caterpillar. We can see them gradually showing their characteristic white, yellow and black stripes. But following hatching, these colors are absent, and the head is black and quite large relative to the body size. Also they have no sensors – those start growing in the first few days.
Here’s a video of the three Monarch caterpillars seen above munching on the flower buds of Butterfly Milkweed:
This video below shows the two caterpillars in the photos munching side by side on the same Swamp Milkweed leaf: