I is for instar. An instar is a developmental phase in the life of an insect. Each instar marks a change in the abilities and characteristics of the insect. Most cicadas go through five instars; the final instar of a cicada’s life is the adult or imago phase.
An imago is an adult, sexually mature insect. Here’s a photo of Magicicada imagoes:
Insectoverdin is the pigment that that makes insects like cicadas green.