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Top 10 Deadliest Spiders

by Jonathan H. Kantor
fact checked by Jamie Frater

Deadliest spiders are a subject that you would think we would have covered long ago, but believe it or not, Listverse has never ranked spiders in this way. We have covered deadly snakes and other venomous creatures, but venomous spiders have be long ignored. Until today.

Before we begin, let’s just quickly clear up one point of confusion: spiders are (usually) venomous, not poisonous. For something to be poisonous, it must be harmful through being eaten. To be venomous, a thing must be harmful by injecting venom—via fangs in the bulk of cases with deadly spiders. Now, on with the list!

SEE ALSO: 10 Fascinating Mysteries Involving Spiders

Across the globe, most people can agree that spiders are critters they want nothing to do with. A fear of spiders, otherwise known as arachnophobia, is one of the most widespread fears people have, and there’s a good reason for it.

Most of our fears don’t stem from irrational places; they come from evolving on a dangerous planet. Even though most spiders are harmless to humans, there are several species capable of killing you with a bite or two, and it’s because of these ten that arachnophobia is anything but irrational.

10 Wolf Spider—Hogna carolinensis

From the family Lycosidae, Wolf Spiders are named for their wolf-like habit of chasing and pouncing upon their prey. There are about 125 species in America and another 50 in Europe, and they typically measure about 2.5 cm (1 inch), with their legs adding about 2.5 cm to their (terrifying) size. They can be black, gray, or brown, and they have one of the most unique features: an eye arrangement with four small eyes in the bottom row, followed by two large eyes in the middle row and two medium eyes in the top row.[1] These venomous spiders are sometimes confused with a brown recluse (both brown in color) or a tarantula (both are hairy). These spiders hunt their prey rather than hang out in their webs, waiting for a hapless insect to meander into the sticky trap. They prefer to establish dens in the ground from which they hunt, dragging their prey back inside. They use webbing to fortify the den, so it can look like a webbed funnel.[2]

Wolf spiders inject venom into their prey to subdue it. And they will bite humans as well, although they don’t prefer to. If a wolf spider does bite a human, the worst thing that will happen is it will leave a red, itchy welt on the skin. This is the body’s natural reaction to the venom injected. Some people, who are sensitive to spider bites, may experience nausea, a rapid pulse, dizziness, or necrosis around the bite wound.[3] If bitten, you should seek immediate medical attention. Although extremely rare, it is possible to die from a bite, depending on how the person’s body reacts.

9 Yellow Sac Spider—Cheiracanthium inclusum

Cheiracanthium Inclusum Yellow Sac spider
Yellow Sac Spiders are widely distributed spiders ranging in size from only 3 to 15 mm (0.1 to 0.67 inch). You’ve probably seen them numerous times over the years and not given them much thought due to their size, but size rarely matters when it comes to spider bites. A Yellow Sac Spider’s venom contains a cytotoxin, which is a nasty substance that impairs call functions, often leading to cellular death. You will immediately know if one bites, as their bites are incredibly painful.[4]

The good news about a Yellow Sac Spider bite is that it’s not going to kill you.[5] You may wish you were dead when the pain hits, but there have never been any reported deaths. These spiders will aggressively defend their territory, and the last thing you want to do is threaten one of their egg sacs. Their venom does cause limited necrosis of the skin in the area where a bit occurs, which often results in a misdiagnosis of a Brown Recluse bite. Some species of a Cheiracanthium’s bite is more severe than others, but the most common are C. inclusum and C. mildei.

8 Brown Recluse Spider—Loxosceles reclusa

Loxosceles Reclusa Brown recluse spider
The Brown Recluse Spider is one of the most feared spiders in the civilized world due to the nature of its venom. While bites from a Brown Recluse will likely not result in the death of a person, it will cause the death of tissue, as its venom is highly necrotic. Much like a rattlesnake bite, the venom of a Brown Recluse will course through your veins at the site of the bite, resulting in the death of the tissue at the bite location.[6] One of the problems with a bite is that it may not be initially felt, nor will it always be immediately painful. The resulting symptoms can be misidentified as a result.

The severity of the necrosis varies, and not all bites result in tissue death. Only 37% of bites will cause skin tissue to die. A small percentage of people may experience hemolysis—the bursting of red blood vessels.[7] The fear of necrosis is what makes these spiders particularly scary to humans, and they are all over the central and southern United States, though they are rarely aggressive. Untreated bites can result in large portions of skin becoming gangrenous.

7 Redback Spider—Latrodectus hasseltii

Latrodectus Hasseltii redback spider
The Redback Spider, sometimes called the Australian Black Widow, is often mistaken for a Black Widow thanks to the similar coloring and red mark found on the backs of females. They are highly venomous with a cocktail of different types of neurotoxins that deliver a staggeringly high amount of pain in humans.[8] Fortunately, they don’t often strike with full venomization, preferring to hold back some of their precious venom for prey animals. If a Redback Spider were to deliver its full load in a bite, it would likely result in death.

That being said, there have been no known deaths attributed to these spiders since the invention of its antivenom in 1956. Before that time, a bite could result in death, which would likely be the same today were it not possible to get the antivenom in time. The dangerous symptoms from a bite include nausea, excessive sweating near the bite, muscle weakness, and vomiting. These spiders aren’t timid, and they will strike a person if they feel threatened, which is what happened to one unfortunate Australian man who encountered one while sitting on a toilet.[9]

6 Brown Widow Spider—Latrodectus geometricus

Latrodectus Geometricus brown widow spider
The Brown Widow Spider is an incredibly dangerous cousin to the more familiar Black Widow. These lovely little beasts carry a particularly dangerous neurotoxin in their venom, which can result in a condition named after the spider’s bite called Latrodectism.[10] The Brown Widow Spider’s venom is more toxic than its famous cousin, but thanks to its stingy nature, it doesn’t completely envenomize humans with a bite.[11] These spiders are particularly shy and will only bite a person who disturbs them, or if they feel threatened.

That being said, a bite from a Brown Widow spider is going to hurt. A lot. There have been no recorded deaths from a Brown Widow bite, but the pain from a single bite has been described as being hit with something “like a sledgehammer.”[12] The venom will cause immediate pain and muscle contractions, and if left untreated in a particularly sensitive location, the bite can result in spinal or cerebral paralysis. Their distribution has become cosmopolitan, and they are found throughout the developed world.

5 Six-Eyed Sand Spider—Sicarius hahni

Sicarius Hahni six-eyed sand spider
The Six-Eyed Sand Spider is a relative of the Recluse Spiders, though it is only found in the deserts of southern Africa. Some consider this the most venomous spider in the world. The spiders are excellent at camouflage thanks to their being covered by tiny hairs called setae.[13] The hairs pick up sand particles to create a sort of ghillie suit it wears as it buries itself under the sand. It sits there, patiently waiting for prey to come along so it can ambush and kill it quickly. These spiders rarely attack humans, but if they do, the bite could be dangerous.

Most bites do not result in envenomation since they prefer to store that for food they can actually eat. That’s a good thing, seeing as their venom contains a cryotoxin capable of destroying tissue and even organs. A bite with full envenomation would likely lead to hemorrhaging followed by liver and kidney failure. Death would come soon after, and there is no antivenom.[14] Fortunately, there are no recorded cases of these shy critters envenoming a bite in humans, but from what we understand of their venom, that’s a good thing.

4 Black Widow Spider—Latrodectus mactans

Handling a Female Black Widow Spider (Latrodectus mactans)

Black Widow Spiders are some of the most notorious arachnids on the planet, and their level of danger can be seen in how much they have invaded our popular culture. The term “Black Widow” has been used to describe a woman who kills her husband(s), while Marvel Comics opted to name a deadly assassin after the little buggers. They are found throughout North America, Central America, Africa, and the West Indies, so there’s a good chance one is crawling up your back right now.

National Geographic[15] lists them as the most venomous spider in North America with a venom that is 15 times stronger than a rattlesnake. A bite from a Black Widow will result in a small pricking of the skin, but don’t let the size of the mark fool you; there’s a dangerous amount of venom coursing through your veins, which can cause severe muscle cramping, nausea, and paralysis of the diaphragm, which can result in difficulty breathing.[16] A bite can theoretically kill infants and the elderly, but no recorded cases of this happening are known.

3 Chilean Recluse Spider—Loxosceles laeta

Brown Recluse spiders are often feared for their necrotizing venom, but they pale in comparison to their Chilean cousins. The Chilean Recluse Spider is considered the most dangerous of all the Recluse Spiders, and their bite can cause some serious damage or even death. Fortunately, like most Recluse spiders, they don’t often interact with humans and only bite if they feel threatened. Their venom contains a dermonecrotic agent,[17] which kills off skin tissue in the area of the bite. When a bite is serious enough, it can cause deadlier issues.

In about 4% of cases, the venom caused a series of failures resulting in death. This can happen if the bite consists of a tremendous amount of venom or if it hits an area near the heart or kidneys. Renal failure is the most common severe reaction to a bite with full envenomation, but these are incredibly rare. Their venom is 15 times more toxic than some species of cobra, and as much as 10 times more potent than sulfuric acid.[18]

2 Sydney Funnel Web Spider—Atrax robustus

Atrax Robustus funnel web spider
While Australia may be known for its larger, more toothy animals, there is one spider that stands as the most dangerous of them all in the land down under. The Sydney Funnel Web Spider is listed by Guinness World Records as being the “most venomous”[19] spider in terms of toxicity to humans. While a lethal dose of venom is currently unknown, the spider’s lethality to the crab-eating macaque has been noted as 0.2 milligrams per kilogram. An average venom yield from a male Sydney Funnel Web Spider is 176 milligrams.[20]

The venom of the Sydney Funnel Web Spider is particularly harmful to primates, which includes humans. The venom contains a compound called δ-atracotoxin, which inhibits a primate’s nervous system, and when they bite, they don’t hold anything back. Snakes typically reserve their venom and don’t deliver it all with a strike, but these spiders are far less conservative. They issue a full envenomation with a bite, and there have been numerous deaths[21] attributed to the Sydney Funnel Web Spider prior to the creation of an antivenom in 1991.[22][23]

1 Brazilian Wandering Spider—Phoneutria fera

Phoneutria Fera Brazilian wandering spider

While many of the spiders on this list are dangerous, the one spider most feared around the world is the Brazilian Wandering Spider.[24] They are different from most spiders in that they hunt their prey instead of setting up a trap using webbing, and its prey sometimes includes humans. Granted, it doesn’t bite humans to eat them, but it probably could if it wanted to. They like to hide inside bunches of bananas where they await a passing prey animal … or human who attempts to harvest some bananas.

If a bite occurs, death will follow in less than an hour if left untreated. Fortunately, they don’t often envenomize their bites with people, preferring to save it for their actual prey. There are some unusual side effects of Brazilian Wandering Spider bites aside from tachycardia, nausea, blurred vision, hypothermia, and death; males may experience a painful erection, which will last for hours. If the embarrassment doesn’t kill them, not treating the bite certainly will, so if you ever find one of these spiders lurking in some bananas,[25] avoid it at all costs.

For more creepy crawly lists like this, check out 10 Fascinating Mysteries Involving Spiders, and Top 10 Bizarre Spiders.

About The Author: Jonathan is a graphic artist, illustrator, and writer. He is a Retired Soldier and enjoys researching and writing about history, science, theology, and many other subjects.

fact checked by Jamie Frater
Jonathan H. Kantor

Jonathan is a graphic artist, illustrator, and writer. He is a Retired Soldier and enjoys researching and writing about history, science, theology, and many other subjects.

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