Last week, I read a Facebook post from a friend who lives in North Carolina. She had posted a pretty photo of a Monarch caterpillar (Danaus plexippus) munching on a leaf. Next to the Monarch was a slightly blurred orange and black caterpillar with fuzzy white ponytails. My friend’s comment was, “They’re growing!”
I thought, “Well, they may be growing, but what are they?” I seemed to remember that after a Monarch caterpillar’s first or second instar, or molting stage, it looks to the untrained eye much like every other Monarch in instars three to five. The Monarch’s appearance doesn’t change appreciably in the later stages as does that of some other species, such as the Black swallowtail. So, what caterpillar was my friend referring to?
Jim and I walked up to the field to check the raised bed where a healthy crop of butterfly weed (Asclepias tuberosa) had fed a bunch of hungry Monarchs this summer. Some of the plants had been stripped of leaves, but half of one plant remained intact, sp...