Their voracious appetites for swan plant leaves (milkweed), since shedding their skins going into the 5th instar, was amazing to see. They ate through many plants really quickly.
These two have been quite comical to observe. They've been the same size, all the way through. Often, although there were several other plants for them to eat, they would perch on the same leaf and eat until they were bumping into each other.
Click on each picture below, to see a larger view.
I made a little video, showing the methodical way in which they eat through a leaf.
The video has not been sped up - yes, this is how fast they eat.