The Most Dangerous Spiders In The World

A world without spiders may sound spectacular to an arachnophobic, but it would actually be an ecological nightmare. From their appetite for crop-consuming insects to the potentially life-saving compounds in their venom, these amazing arachnids actually make the world a friendlier neighborhood.

That's not to say, however, that it's completely nonsensical for humans to fear the 45,000-plus known species of spiders in the world (via National Geographic). A 2017 study suggested that arachnophobia may have been an evolutionary response to keep humanity on its toes when it comes to spiders. Considering how certain species of lethal spiders may have been more common during our evolutionary history, this does make sense.

In reality, spiders rarely bite and are just as eager to avoid you as you are them. Furthermore, antivenom now exists for various types of spider venom. Still, that's no reason to tempt fate and mess around with spiders — especially any of the following species, which all prove the wisdom behind the old adage, "An ounce of prevention is worth a pound of cure."

In 1957, W. C. Reeves was jolted awake at 3:45 a.m. by a "sharp, penetrating pain" under his right eye. He quickly discovered the source of his pain — a pale-yellow spider less than half an inch long. He soon experienced throbbing pain from his cheek to his jaw, an ordeal that lasted nearly 12 hours. A doctor from the American Museum of Natural History identified it as a juvenile Cheiracanthium spider, wrote Reeves and his colleague D. P. Furman in their paper. The authors found 14 of these so-called yellow sac spiders in Reeves' residence in North America.

There's no doubt that a yellow sac spider bite can cause immense pain, in the form of inflammation, headaches, or nausea. What many seem to disagree on is if its venom really causes the death of body tissue (necrosis). A 2006 paper provided evidence to the contrary — researchers examined 20 confirmed yellow sac spider bites and found that none of them resulted in necrosis.

While their venom doesn't seem to be particularly lethal, there are other ways yellow sac spiders may bring about dangerous situations. BBC reported that in 2014, major car manufacturer Mazda issued a voluntary recall notice on certain models, after reports that the smell of petroleum emanating from the cars kept attracting these spiders. The yellow sac spiders would take up residence inside the vehicles' canister vents, resulting in pressure buildup, blockages, and a massive fire risk.

When people think of deadly spiders, the black widow spider is typically very high on the list. Its striking appearance — a sleek, shiny, all-black body with a splash of red on its abdomen that's shaped like an hourglass — evokes a sense of danger that has made the species quite infamous. And while a number of spiders worldwide bear the name "black widow," the first one that comes to most people's minds is the one that's abundant in North America. 

According to National Geographic, a black widow spider's venom is 15 times more potent than a rattlesnake's and is enough to kill young children, the elderly, and people with deteriorated health. From a small bite that reportedly "feels like a pinprick to most people" (via LiveScience), pain can start within minutes, followed by nausea, muscle aches, paralysis of the diaphragm, seizures, and (on very rare instances) death. Since the development of antivenom, however, fatalities due to black widow bites have significantly decreased (via Annals of Pharmacotherapy).

Just like the katipō spider, females of this species are far more dangerous than the males. Aside from their potent venom, they're also well-known for their tendency to slay and devour their mates (hence the name "black widow"). It's fortunate that black widow spiders don't simply bite people out of the blue. They only endanger a human's life when they sense that said human is about to endanger theirs.

Meet the red widow spider, one of the most dangerous spiders in the world ... that you're unlikely to ever encounter. In fact, there is no record of this spider ever causing serious harm to a person, according to James Carrel, a biologist at the University of Missouri.

Save for its black abdomen, this rare species is red all over. It lives exclusively in certain parts of Florida, including the Lake Wales Ridge and the Atlantic Coastal Ridge. Due to its limited distribution and conservation status as a vulnerable species, conservationists such as the Florida Natural Areas Inventory have been keeping an eye on this spider. Which, in a literal sense, is not an easy task. Red widow spiders build their webs in the unopened leaves and shrubs of palmetto plants, making them terribly hard to spot unless it's a foggy morning. Based on Carrel's observations, red widow spiders prefer snacking on five Florida-endemic species of scarab beetles.

The red widow spider reportedly possesses venom comparable to that of a black widow's, but since they're so hard to find in the first place, Carrel believes that there's a "near zero" chance that anyone would accidentally encounter (or get bitten by) a red widow spider. If anything, its inclusion on this list emphasizes that just because something is dangerous doesn't mean it's automatically a threat.

Before you start wanting to give all these poor, misunderstood spiders a hug, here's one that might make you change your mind — the Chilean recluse spider, which the Australian government's Pest and Disease Image Library cites as one of the most dangerous of the recluse species.

Like other recluses, the Chilean recluse spider sports brown coloration and back markings. Aside from its larger size, it's not that easy to tell it apart from other recluse spiders at first glance. This species is native to South America, where locals call it "violinist spider" and "corner spider" (via Murcia Today). Like its North American relative, it's a fairly common sight in Chilean households. In fact, according to T13, there's at least one in every two homes in the country.

Cobra venom reportedly has nothing on this toxic spider's bite, which is allegedly 10 times worse than highly corrosive sulfuric acid. CBS News reported a case shared by the Centers for Disease Control in which a Chilean recluse spider victim showed severe necrosis just a week after getting bitten. More often than not, patients survive this excruciating experience with severe, long-lasting scars. In extremely rare cases, bite victims die (via Chile Today). Fortunately, just like the other dangerous species on this list, the Chilean recluse spider is not an aggressive attacker. It will almost certainly bite, however, if it feels threatened.

Fairly common across mainland Australia, mouse spiders are trapdoor (burrowing) spiders. A typical suburban sight, mouse spiders got their moniker from the misconception that they could dig holes as deep as their rodent namesakes (via Junior Rangers Review). Another mistake that many people have made about them — they're frequently misidentified as Sydney funnel-web spiders, according to the Australian Museum.

That's not to say, however, that mouse spiders are slouches in the toxicity department. In fact, the Australian Museum describes their venom as "very toxic," close to being as lethal as their lookalikes. Some reported cases of mouse spider bites have even resulted in symptoms "similar to funnel-web spider envenomation."

Over the years, however, there haven't exactly been that many reports of mouse spider bites. Some experts even say that they tend to inject less venom (or sometimes, none at all) when they bite. Regardless, guidelines from the Australian government require all suspected mouse spider bites to be treated as if they were inflicted by funnel-web spiders. Better safe than sorry, right?

Truth be told, "dangerous" is a relative term. Disturb any of the spiders listed here, and you're in for a world of hurt. But if there's one spider on this list that could qualify as the most potentially dangerous, the relatively little-known six-eyed sand spider would probably be the strongest contender, for a number of reasons.

At first glance, this desert-colored spider looks rather unassuming. You might even find its habit of burying itself under sand (a clever camouflage technique for hunting prey in its sandy Southern African habitats) endearing. Unfortunately, experts know very little about this species. However, what they do know is quite frightening.

Studies from 1997 and 2020 have shown that certain spiders produce venom like the kind that recluse spiders inject — meaning the hemorrhage-causing, tissue-decaying, cell-killing variety. According to a piece by Jordan Pendergast, the venom can severely damage vital organs such as the kidneys and liver, eventually leading to death. There are at least two documented cases of six-eyed sand spider bites — one victim died, while the other lost a limb (via Go Science Girls). Oh, and by the way, no antivenom currently exists to counter the six-eyed sand spider's potentially deadly bite. Hopefully, that can make you think twice before getting one of these as an exotic pet.