You can clearly see the bite out of the connected leaf top stem which causes the leaf to lie down straight before the caterpillar pupates. The miracle of the transformation from egg to butterfly staggers my imagination and it is wonderful to be able to follow it in my garden.

Watch a caterpillar flagging a leaf on my swamp milkweed (asclepias perennis). https://youtu.be/M4ey_Dm2dk0 I have read the asclepias perennis is a monarch caterpillar favorite.