By now, you may know that lemmings don't really commit mass suicide. But did you know that ants sometimes do? In the video above, a few dozen army ants (species Labidus praedator) engage in an creepy ritual entomologists call an "ant mill." Unless something disrupts their spiraling path, they'll keep following it until they die from exhaustion.
How did they get in this mess? The ants are blind, and they navigate by following scent cues left behind by other ants, as Sanford Porter, a research entomologist with the USDA-ARS explains in a Discovery Channel video. Each follows the odor trail of the ant ahead of it--so if the leader loops around and starts following another ant in the group, a death spiral can result.
Biologist and insect photographer extraordinaire Alex Wild noted on his blog that this sort of behavior can arise from such simple situations as a few ants exploring a coffee cup. But it can also be huge—one spiral, 1200 feet in circumference, was observed by American naturalist William Beebe in Guyana in 1921.
It may seem like an evolutionary glitch, but the fact that ants aren't big on critical thinking actually has some interesting applications. Ants' behavior is generally determined by only a few simple rules, such as "follow the ant in front of you," and this makes them a useful model in some artificial intelligence simulations. These so-called "ant colony optimization" algorithms use ant-like objects to solve problems such as finding the most efficient route through a maze. Since 'bugs' like the ant mill can be a big problem in those simulations, programmers usually add safety measures to keep the ants on track.
<em>Triatoma infestans </em> Look out for it in: Mexico, Central and South America Why you should fear it: Assassin bugs transmit Chagas disease, a long-term, chronic disease that can ultimately cause serious cardiac and digestive problems. Notorious victim: Charles Darwin met one on his first trip to Argentina.
<em>Lonomia obliqua </em> Look out for it in: Brazil, Argentina, and neighboring countries Why you should fear it: The caterpillars release a powerful toxin that can cause internal bleeding and massive organ failure. Notorious victim: A young Canadian tourist walked barefoot through a resort and stepped on five. Although local hospitals carried an antivenin, she didn't seek treatment until she returned home--a mistake that cost her her life.
<em>Culicoides spp. </em> Look out for it in: Everywhere. Why you should fear it: Also called no-see-ums, biting midges are a serious annoyance in the Scottish Highlands--so much so that tourists check the Biting Midge Forecast before heading out for a round of golf or a trek to a distillery. In Brazil and around the Amazon, they transmit Oropouche fever. Notorious victim: According to a community study, the biting midge broke up marriages in Hervey Bay, Australia, presumably because couples were forced to spend more time indoors together.
<em>Paederus sp. </em> Look out for it in: Most of the world. Why you should fear it: The beetle lands on the skin but doesn't bite. People tend to want to slap it, which releases a nasty poison called pederin that causes horrible blisters and welts. Notorious victim: Our troops stationed in Iraq. The beetles tend to swarm around the bright lights at military bases.
<em>Vespa mandarina japonica</em> Look out for it in: Japan, China, Taiwan, Korea Why you should fear it: Stings deliver a powerful neurotoxin that could be fatal. Notorious victim: Dr. Masato Ono, the world's leading expert on the giant hornet, said the sting felt like "a hot nail through my leg."
<em>Taenia solium </em> Look out for it in: South America, Africa, Asia, and parts of Europe and North America Why you should fear it: While modern livestock management here at home has practically eliminated tapeworm-infested pork, the tapeworm eggs can be spread directly from one infected person to another. How? Let's just say that it's really, really important to wash hands after going to the bathroom-- and leave it at that. Notorious victim: A woman in Arizona went into surgery thinking she had a brain tumor, and woke up later to learn that the cause of her problems had been a tapeworm, not a tumor.
<em>Ixodes scapularis </em> Look out for it in: Eastern United States (other species that transmit Lyme are found in the West and in Europe) Why you should fear it: The nymphs transmit the miserable and difficult-to-treat Lyme disease Notorious victim: Polly Murray, a resident of Lyme, Connecticut, battled the disease for decades and led the fight to get it properly identified, diagnosed, and treated.
<em>Tunga penetrans </em> Look out for it in: Tropical beaches in Latin America, the Caribbean, India, and Africa. Why you should fear it: Tiny fleas burrow under toenails and lay eggs, creating awful sores and possible infection Notorious victim: Members of Christopher Columbus' crew were made so miserable by chigoe fleas that they cut off their own toes to get rid of the bugs.
<em>Centruroides sp. </em> Look out for it in: Southern United States, Central and South America Why you should fear it: The venom can cause severe pain, difficulty breathing, and can be fatal to small children. Notorious victim: A little boy vacationing with his family in Mexico stepped on a scorpion in his shoe. He was flown to a hospital in San Diego, placed on life support, and did survive.
<em>Cimex lectularius</em> Look out for it in: Your bed Why you should fear it: After hearing about all these other nasty creatures, you aren't still worried about bed bugs, are you? Bed bugs may be annoying, but they are not known to transmit disease. They may cause a dreadful allergic reaction, but you'll survive. Bed bugs have always been around; overuse of toxic pesticides drove them away for a few decades, but fortunately, we now realize that the chemicals were far more dangerous than the bugs. Notorious victim: You.