The young cats do look very much like bird droppings and that is how they prevent themselves from being eaten by higher predators like birds. However, they are really voracious eating machines that devour a whole lot of leaves and I am always amazed by how fast they can grow in a single day. I find it very amazing that despite me watching them so closely, they were able to develop from one instar to another distinctly different instar within a matter of hours with me failing to see the gradual transition.
Just a few days ago, I transferred 5 of the 6 cats to the bigger host plant and by then, the 2 earlier cats were no longer present. One of my peeves about the cats is that they always crawl elsewhere to pupate and I lose track of them after that. I would love to watch the pupation process and the eclosion, but unless I deliberately transfer the 5th instar to a container, I never get to see the pupa and eclosion.