Gray cicadas (Cicada orni) use their eyes only in the adult stage when they emerge from the ground and leave the larval state to become imagos. The cicada larvae are blind as sight is useless to them in the underworld in which they evolve for several years, two or three when the soil is rich in food, six if it is poor in roots, and up to seventeen for the Tibicina septendecim species from North America. Their sensory hairs and their large antennae allow them to find their bearings in the darkness of their galleries.