In both the larval and adult stages, cicadas feed exclusively on sap from trees, plants, or roots they suck thanks to their proboscis or rostrum. It consists of a sort of syringe or a hard tapered straw that is part of their face and that they plant in the roots or the plants. Cicadas do not feed on any fly nor worm, contrary to what Jean de La Fontaine's fable claims. Of all the stinging and sucking insects in the world, cicadas are the only ones not harmful to the plants on which they feed.