Spiders are some of the most successful arthropods on the planet, having colonized every continent except Antarctica.
Not all of these eight-legged arachnids are venomous, but some can be deadly to humans.
From the notorious black widow to the ultra-deadly funnel web spider, here are some of the deadliest spiders on Earth.
Latrodectus geometricus is the scientific name for the brown widow spider. It looks similar to its infamous "cousin" the black widow, right down to the hourglass-shaped marking on its abdomen, but there are some key differences. The brown widow’s marking is orange and yellow rather than red, and as their name suggests, they predominantly have tan and brown mottling and a spiky, rather than smooth, appearance. Believed to originate in South America, the brown widow spider is found all around the world.
The brown widow's venom is less toxic than that of its black cousin. However, it can still be deadly. Although they don't deliver as much venom as a black widow, the brown widow's bite can still cause latrodectism due to its neurotoxic venom. Symptoms of lactrodectism include pain, perspiration, muscle rigidity and vomiting.
Living mostly in sand dunes in Central and Southern Florida, the red widow spider (Latrodectus bishop) is another member of the notorious "widow" family. Their venom is just as lethal as brown and black widows, but as they live so far from human contact there has been no recorded bite in medical literature. The female red widow spider's venom is a neurotoxin which is thought to cause prolonged muscle spasms.
The red widow spider has a red-orange head and legs and a black abdomen with yellow rings around red dots. Rather than an hourglass marking like its "cousins," the red widow usually has one or two red marks.
Due to its strikingly similar appearance, the redback spider (Latrodectus hasselti) was once thought to be a sub species of the black widow spider, but it is a distinct species. Also known as the Australian black widow, you can find this creepy crawly throughout Australia, Southeast Asia and New Zealand. The redback spider has even been found in Japan, the United Arab Emirates and Belgium due to inadvertent introductions.
Highly venomous, the bite from the female redback spider can be life-threatening. Using its fangs, it injects a complex venom that causes intense pain at the bite area, in addition to sweating and goosebumps. As time goes on, these symptoms worsen and there may also be redness and swelling, as well as nausea, muscle twitching, headache and fever. Respiratory failure may occur in severe cases. Thankfully, in 1956 scientists released a redback spider antivenom which is very effective, even when used several weeks after the initial bite. No deaths have been reported since.
Normally in the world of spiders it is the female that is more deadly, but for funnel-web spiders (Atrax) the male has the more toxic bite. Any attack must be treated quickly with antivenom, especially if a child has been bitten. There have been several recorded fatalities due to the venomous bites of the funnel-web spider, with death occurring within the hour after being bitten. However, since the development of the antivenom in 1981, there haven’t been any more recorded deaths. Predominantly located in southeast Australia (Sydney), funnel-web spiders are also found in New Zealand, Chile and Europe.
Interestingly, animals such as cats and dogs can actually survive a funnel web bite – it takes about 30 minutes for their body to neutralize the toxin – it's just humans who have such a severe reaction. This venom effects the nervous system and causes symptoms such as an elevated heart rate, numbness/tingling of the mouth and difficulty breathing.
Found in deserts in southern Africa, the six-eyed sand spider (Hexophthalma hahni) buries itself in the sand to ambush unsuspecting prey. The small, stiff hairs that cover the spider helps to hold sand particles in place, adding to its camouflage. It's otherwise known as the six-eyed crab spider due to its crab-like legs.
Another arachnid that produces venom with necrotic effects, the six-eyed sand spider is the most venomous of any of its arachnid relatives, toxicology studies reveal. Scientists have found that there are proteins within their venom that can cause tissue destruction, blood vessel leakage, and thinning of the blood. No antivenom currently exists.
Black in color with stocky, thick legs and a distinctively bulbous head and jaw regions, the mouse spider (Missulena) looks a lot more frightening than its name sounds. One species is located in Chile, another in South America and the rest distributed throughout Australia. They live in soil-covered burrows, popping out the hinged trapdoor top to attack prey.
Their hard, large fangs can cause a deep and very painful bite. However, while scientists believe that the venom of the mouse spider is very toxic, it is rarely injected. As so few cases have been reported, it is thought that mouse spiders don't use a lot of venom or may even "dry bite." Fortunately, funnel-web spider antivenom has proven effective in cases of mouse spider bite.
In the genus Latrodectus, the black widow is one of the most venomous spiders and is found on every continent except Antarctica. In North America, they're commonly found in southern Canada and in the northeastern United States. You can identify the female black widow spider by its shiny black body and distinct red hourglass-shape on the underside of the abdomen. The male black widow is smaller in size, brown or gray in color with small red sports and does not have the hourglass marking.
While both male and female black widows are venomous, only the female is dangerous to humans. The venom of a black widow is reported to be 15 times stronger than that of a rattlesnake, although they don’t deliver as much venom in their bite, so fatalities are rare. That’s not to say a black widow bite isn’t painful! Those unlucky enough to be bitten by a black widow will experience nausea, fever, sweating, restlessness, muscle cramps and labored breathing, and these symptoms may last for several days.
As their name suggests, brown recluse spiders (Loxosceles reclusa) have a shy nature and tend to hide away in dark, sheltered places. However, the brown recluse spider will bite if they feel threatened, and their bites can be deadly. They are usually found in the south and central United States, spanning southeastern Nebraska to southwestern Ohio, south to northwestern Georgia and into Texas.
The brown recluse spider can be dangerous to people because their venom contains a toxin that can cause skin necrosis (rotting). For the most part, symptoms, such as burning and itching at the bite site, as well as fever and nausea, develop a few hours after a bite. In extreme cases, the venom can lead to serious reactions or even death, especially to more vulnerable groups such as young children and the elderly.
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