Cicadas comes as a signal of safety. They come in the form of song or rhythm – this is similar to the resonance and vibration of cricket.
The Cicada talks of timing: this is the right place, the right time. Their cycles are responses to cues in the environment, and happen at regular intervals (or have in the past) of 7 and 17 years. What 7 and 17 year cycles are you repeating right now?
Cicada is a translator from trees to humans, a means to give the plant people a voice, by having the cidadas (and frogs and crickets) sing the song that the tree people want to hear.
Additionally, cicada speaks of a strong community. The drone of a cicada is kept constant, by having the entire community sharing the vibration. It ebbs and wanes, circles around the trees, but it is always there, reliable.