The smallest caterpillar just completed a molt. This period between molts is called an instar.
The medium caterpillar is eating milkweed and gaining size.
The largest caterpillar has become plump. I think that she may pupate soon!
Outdoors, the curled caterpillar became a chrysalis. He is hanging beneath a milkweed leaf on the Hellstrip.
And, I spotted another large caterpillar enjoying the milkweed by the front steps.
Most Monarch butterflies only live for two to six weeks. But, the last generation of the year, can live up to nine months. The caterpillars that we see today are part of the last generation. They will emerge and become part of the Great Migration