I say “antennae-like” because my friend and butterfly consultant, Dr. Daniel Najera, a PhD in Entomoloy from the University of Kansas, Lawrence, informs me that the word “antennae” is not appropriate for describing all of these interesting extensions.
Apparently antennae have special sensing powers while tentacles are just for show. Part of the reason for this is to throw off predators (and I’d like to think to amuse us observers). So technically (or should I say tentacle-ly?) only the set of protuberances on the head of the caterpillar are antennae, while the others are tentacles.
Got all that?
And now, for the photos. Queen–above. One set of antennae + two sets of tentacles = three antennae-like protuberances.
Monarch–below. One set of antennae + one set of tentacles = two antennae-like protuberances.
Glad we got all that straightened out.