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Swarms & Infestations

The biggest, strangest, and most surprising animal events we’ve found in this category—plus the reason they happen.

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Mass emergence

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.

Eastern United StatesPeriodical cicada

Population outbreak

Swarms & Infestations

When Mormon crickets take over Nevada roads

During outbreaks, enormous numbers of Mormon crickets can cover roads, yards, and agricultural areas, sometimes creating a genuine driving hazard.

Nevada and the western United StatesMormon cricket

Mass insect emergence

Swarms & Infestations

Lake Erie can release billions of mayflies in a single night

Mass mayfly emergences can become so large that radar detects them and shoreline communities wake up to streets and buildings covered in insects.

Lake Erie and the Upper Mississippi RiverBurrowing mayfly

Migratory pest swarm

Swarms & Infestations

A single square kilometer of locust swarm can hold tens of millions of insects

Desert locust swarms can stretch across huge areas, travel long distances in a day, and consume crops at a scale that turns an insect outbreak into a regional emergency.

Africa, the Near East, and Southwest AsiaDesert locust