My backyard in Victor, NY has produced 48 caterpillars so far. The Milkweed that started from just one seed blowing into the garden has become almost a pest. If it weren't for the power that it has to attract the Monarchs I would have tried to remove it long ago.
The Caterpillars began to hatch as tiny worms that could barely be seen with the naked eye. The eggs are small white circles typically laid on the bottom of the milkweed leaves. They take 4-5 days to hatch after being laid by a passing mother who then flys off to visit more plants and lay as many eggs as she can.
The three pictures above show the early stages of growth. The Monarch egg, a newly hatched Caterpillar, and a young Caterpillar. As they eat more and more they grow to about 2 to 2 1/2 inches. At this point they attach to a leaf or other high place and transform into a Chrysalis.
The bright Green Chrysalis has 3 distinct gold spots near the bottom and a crown of gold around the top. Hence the reason for their name as a Monarch always wears a crown of gold.
Look closely at the Chrysalis and you can see the butterfly wings within.