Cicadas are large insects that typically live in trees. They eat sap, making trees the most logical place for them to live. In addition to feeding off of the trees, they also use trees to bear their young, laying their eggs in openings in the bark.
Even if you don’t know what a cicada looks like, you have probably heard them before. Cicada’s are extremely loud, singing at night to avoid predators.
Cicada’s are famously known for remaining dormant, and only emerging about every 17 years. When they do emerge, they show up in amazingly massive numbers.