I just discovered — what I thought were Monarch caterpillars (in previous post) are really Eastern Swallowtails. My mistake — still, do have a few Monarch caterpillars who are on the right plants in the garden.
The “horns” are biggest give-away. When you bother the little creatures, they pop out scary orange protuberances. They also like herbaceous plants — fennel in particular.
Thanks to Texas Butterfly Ranch and photographer Monika Maeckle for clarity and great demo!