Cicadas are insects often associated with warm weather, especially the heat of summer. That’s because, in more temperate parts of the world, certain species of cicada live underground for over a decade until they emerge and reproduce in the warmer months.
In the northeast United States, these periodic cicadas are quite common and individual cicadas emerge every 17 years. So, every summer, cicadas that were born 17 years prior finally emerge from the soil and become adults. When this happens, billions of cicadas emerge at once, and the swarms are quite impressive (and loud). In some areas, they can reach 1.5 million cicadas an acre!
Luckily, aside from making a tremendous din, cicadas are not pests. They don’t eat crops (although they occasionally feed upon tree sap); they just want to have sex and die. That’s the whole reason why they’re so loud. Males produce the loud sounds to attract females!