"I have found on my milkweed, among "normal" monarch cats, a caterpillar with a slightly different color pattern and an extra set of antennae about mid-back. Please forgive my ignorance, but what is this?"
You have found a Queen butterfly caterpillar. Queen butterflies are also in the Danaus family, like Monarch butterflies. In the extreme south, Soldier butterflies can also be found.
Learn more about Queen butterflies!
