How can you tell if a Magicicada periodical cicada nymph is ready to molt?
Answer: look for two black spots on its back (technically the cephalothorax). They look like they are wearing aviator sunglasses pushed up on their forehead!
I do not know the official name for these spots, but they seem to be related to the pigment that turns the cicadas black after they molt. They may scare away predators that think the spots are big eyes!
Here are a few ideas for a name for them:
obscuras maculas
mutatione macularum