Originally Posted by
JMO
The immature life stages of the cicadas (and other Homopterans, or the Hemipteran true bugs) are called nymphs, and the cicada nymphs do live underground and feed on sap along the tree's roots. The nymphs' mouthparts are not vestigial or non-functioning, but they are dagger-like for "piercing-sucking", and probably change in length and configuration at each nymphal life stage (called an "instar"). As the nymphs feed and grow underground, in the case of cicadas for many years (up to 17 for the broods that will be making all the racket this summer), the nymph must molt and shed its previous cuticle, and transition to the next life stage or instar (the transition process is called "metamorphosis"). Since Homopterans and Hemipterans have a life cycle that is considered "incomplete metamorphosis," they do not have a pupal stage between the immature nymphal stages and the final adult and reproducing stage (as we are familiar with moths and butterflies emerging from a pupal case, or also called a chrysalis).
The cicadas that we will see emerging from the ground this summer will be the last instar nymphs, and they will crawl up the stems of their host tree and molt for the last time in their life cycle, into the adult stage (which is fully sexually competent). So along the stems of the trees (or laying on the ground below) you will be able to find many empty cast skins (or more properly called, nymphal cuticles), and then you'll be able to see the recently emerged adults whose bodies are not yet fully formed and hardened, and when that process is complete the fully formed adults with their expanded wings. The fully formed males will be making all the noise with their calling, hoping to attract females. And both adult sexes will be busily flying about until they can find a mate(s). The adults probably don't feed on the sap of trees very much, if at all. The adult females are equipped with a substantial saw-like ovipositor that they use to chisel grooves that look like splinter pockets in the bark along the more tender, young shoots or branches of their host trees. Each female can lay about 20-48 eggs in each of about 20 or more splinter pockets. After the eggs hatch, the first stage nymphs will drop to the soil and burrow below the surface to feed on the sap in whatever tree roots they are lucky enough to find, and get their piercing-sucking mouthparts into. And with much more luck, the nymphs will survive to become adults and repeat the cacophony 13 or 17 years later.
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