Ten Terrifying Animal Swarming Experiences

When animals get together in numbers, they become a different beast altogether. Often deadly, almost always injurious, and without fail horrifying to behold, the best place to be when a swarm starts up is, well, somewhere else. In rough order of death toll, here are the ten worst encounters with swarming animals we could find.

1. The 2013 Chinese Hornet Attacks – 42 Dead, 1,600 Injured

In 2013, the Chinese city of Ankang, located in Shaanxi province, was gripped by panic as swarms of Vespa mandarinia—commonly known as the Asian giant hornet—unleashed chaos. These two-inch-long monsters attacked indiscriminately, often in open areas like schools, farms, or city parks. Victims described hornets pursuing them relentlessly, even as they tried to flee.

What made these swarms truly terrifying wasn’t just their size or aggression, but their venom. Victims suffered multiple organ failure due to the sheer toxicity delivered through repeated stings. The government eventually deployed fire crews and special pesticide units to destroy thousands of nests. It was a war—man versus swarm—and for too many, it came too late.

2. The 1988 Brazilian Army Ant Incident – Dozens Overrun

In the heart of the Amazon, local villagers are accustomed to the rhythm of nature—but when that rhythm becomes a roar, it’s time to run. In 1988, a military unit stationed in the rainforest underestimated a moving column of Eciton burchellii, commonly known as army ants. These flesh-stripping insects operate as a living mass, able to skeletonize frogs, birds, or even large mammals.

The ants swarmed a temporary encampment at night. Several soldiers, asleep in hammocks or on the ground, were overwhelmed. Though official numbers are vague—this was a military mishap, after all—reports suggest at least a dozen fatalities and many more severe injuries from panic, allergic reactions, and trampling as troops attempted to escape.

3. The Killer Bee Massacre, Texas, 2013 – 1 Dead, 5 Injured

Africanized honeybees, often called “killer bees,” are a hybrid species known for their hyper-aggressive defense strategies. In 2013, a Texas man was killed after disturbing a hive estimated to contain over 40,000 bees. His body was found covered in stings. Emergency responders described the scene as surreal: a dark, moving cloud of rage.

These bees don’t just sting once—they sting repeatedly, and they chase intruders for up to a quarter of a mile. The man’s horses were also stung to death, underlining the swarm’s lethal power.

4. Locusts of East Africa, 2020 – Crops Devoured, Famine Threatened

While locusts don’t typically kill humans directly, their swarming behavior has led to immense suffering. In 2020, East Africa faced one of the worst desert locust plagues in over 70 years. Billions of locusts—each capable of consuming their body weight in food daily—moved across Kenya, Ethiopia, and Somalia.

The swarm blanketed fields, stripped trees, and consumed entire harvests in minutes. For millions of already food-insecure families, the locusts didn’t just ruin a season—they destroyed hope. While not a horror of blood, the psychological and societal damage was immense, pushing entire regions closer to famine.

5. The 1974 Quelea Bird Swarms – Agricultural Collapse in Africa

The red-billed quelea is often called the most numerous bird on Earth—and in 1974, parts of Sub-Saharan Africa learned why that’s a problem. In Sudan and Chad, clouds of quelea descended on grain fields. One swarm was measured at over 30 million birds. The birds devoured millet, sorghum, and wheat in minutes.

Though no human lives were directly lost, widespread food shortages followed. The FAO (Food and Agriculture Organization) compared the birds to a living locust swarm. Governments used napalm and even jet fighters to try and break the infestations.

6. Driver Ants in Uganda, 2001 – Children Suffocated in Their Sleep

Driver ants, or Dorylus, are infamous in Africa. In 2001, a Ugandan village awoke to tragedy when a swarm infiltrated several homes during the night. These ants are known to swarm en masse—millions of them in a living river. Unfortunately, their small size allows them to crawl through cracks in walls and into bedding.

In one home, three children were found dead, having suffocated after inhaling or being covered by the ants. Villagers reported being driven from their homes entirely, some sustaining severe bites in the process. The psychological impact lingered far longer than the physical wounds.

7. The 2021 Cicada Invasion, U.S. – Chaos on the Roads

Every 17 years, the Brood X cicadas emerge in their billions. Though largely harmless, in 2021, their sheer numbers caused unexpected mayhem. Cicadas splattered across highways, their slick bodies making roads dangerous. In one instance in Ohio, a motorcyclist crashed fatally after a cicada struck his face shield, causing him to lose control.

Airports delayed flights as engines risked clogging. Outdoor events were canceled due to deafening mating calls reaching 100 decibels. While not traditionally “horrifying,” the swarm was a vivid reminder that sheer volume can be a force of nature.

8. Jellyfish Swarms, Japan 2009 – Fishermen Overturned, Poisoned

Japan’s coastal fisheries were blindsided in 2009 by an enormous bloom of Nomura’s jellyfish, each weighing up to 450 pounds. These creatures flooded the Sea of Japan, capsizing small boats and devastating the fishing industry. One boat was overturned when three men attempted to haul up a net only to find it full of jellyfish weighing several tons in aggregate.

Stings from the jellyfish hospitalized dozens of fishermen. The swarm’s size—measuring hundreds of miles across—meant that no safe harbor could be found. Some scientists blamed ocean warming, but the fishermen blamed the creatures themselves.

9. Bat Cave Incident, Thailand 2010 – Suffocation and Collapse

Thailand’s limestone caves are home to millions of insect-eating bats. In 2010, a group of inexperienced tourists and a guide entered a poorly ventilated cave just before sunset, unaware that it was a bat emergence site. As the bats swarmed out—millions of wings beating in unison—the cave’s limited airflow reversed.

The result was horrifying: the bats’ carbon dioxide and ammonia-rich guano gases, combined with reduced oxygen, caused disorientation, fainting, and eventually suffocation. The guide and two tourists died. The rest barely made it out, some suffering long-term respiratory issues.

10. The Antelope Stampede, Kazakhstan, 1997 – Trampled by Panic

Though not a classic “swarm,” herd stampedes act with a single, terrifying purpose: escape. In 1997, a group of eco-tourists in Kazakhstan found themselves caught in the middle of a massive saiga antelope migration. Spooked by helicopter noise, the antelope—numbering in the tens of thousands—bolted.

The tourists were on foot, and several were knocked down. Two died from blunt-force trauma and trampling injuries. What made it chilling was the herd’s collective decision-making. It moved like water, crushing everything in its path. No amount of shouting or movement diverted the oncoming wave.