Swarms & Infestations
Why cicadas can suddenly seem to be everywhere
A synchronized emergence can turn trees, sidewalks, fences, and backyards into a wall of sound and movement.
Video: BBC Earth. Embedded from the original YouTube source.
The mechanism
Why this happens
Periodical cicadas spend most of their lives underground and emerge in synchronized groups after long developmental cycles.
Season & place
Where this event happens
Eastern United States · Mass emergence. Timing and local conditions can vary from one occurrence to the next, so current local guidance matters when planning around a recurring event.
The apparent invasion is really a synchronized life-cycle event. Large numbers emerge, molt, mate, lay eggs, and disappear within a relatively short seasonal window.
What to know
- A huge emergence is temporary.
- The insects are not arriving from somewhere else; they have been developing underground.
- The sound comes mainly from males calling to attract mates.
If you go
Watch without becoming part of the problem.
Follow local closures and wildlife guidance, keep a responsible distance, avoid blocking migration or access routes, and do not disturb roosts, nesting areas, dens, or concentrated animals for a photo. Conditions and access rules can change quickly.
Good questions
What people usually want to know
Why are cicadas everywhere all at once?
Periodical cicadas synchronize their emergence after spending years underground, so huge numbers can surface in the same region at nearly the same time.
How long does a cicada invasion last?
The visible adult phase is temporary and generally lasts only part of the season in a given location.