Tawny Emperor vs Hackberry Emperor Caterpillars
I see this come up every once in a while: somebody sees an Asterocampa caterpillar but doesn't know which one. It doesn't help that the definitive caterpillar guide, Caterpillars of Eastern North America, has an entry for Tawny Emperor but includes pictures of BOTH caterpillars and it's not immediately clear without a close reading of the text which is which.
Since I had one of each, the same age, I figured I would put them side by side for a comparison. Keep in mind there are subspecies for each and they can look very different in terms of body pattern (don't get me started on the ID tips for Tawny Emperors being exclusively for the Florida subspecies, sigh), so you want to look at the structure of the head and the relative size of the horns/hornlets.
L: Tawny Emperor R: Hackberry Emperor
L: Tawny Emperor R: Hackberry Emperor
Top: Tawny Emperor Bottom: Hackberry Emperor
L: Tawny Emperor R: Hackberry Emperor
NOTE: The color and pattern of the face will change with age (molting) and varies between individuals. That said, the patterns on striping on the faces are distinct between the two.
And the most important part:
L: Tawny Emperor R: Hackberry Emperor