Are cicadas good for anything?
In this regard, what is the purpose of the cicadas?
The cicada's purpose in terms of trees: Cicadas provide trees a service by pruning the weak branches of a tree. Cicadas lay eggs in the branch, weak branches wither and die (“flagging”), and the tree benefits from that by not having to waste energy on a weak or diseased branch.
Also know, why do cicadas only come out every 17 years?
One Of These Broods Is Not Like The Other But if periodical cicadas only emerge every 13 or 17 years, why do we see them every year? It's because they don't all emerge at once. Each of these broods emerge in different years, so residents in cicada regions rarely spend a summer without them.
The chirping and clicking noises of the male cicada are actually a species-specific mating call that can be heard by females up to a mile (1.6 kilometers) away. The cicada's group chorus also repels birds that hunt by day, so when these insects stop singing, there's a good chance the birds have gone to bed.