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The 5 Most Frightening & Dangerous Spiders in Costa Rica

most dangerous spiders costa rica
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A place of rugged rainforests and long stretches of sandy coastline, Costa Rica is a jewel in the crown of Central America. With roughly a quarter of the country made up of protected jungle, Costa Rica is teeming with wildlife. In fact, it’s one of the most biodiverse places on Earth, accounting for 5% of the World’s biodiversity. Home to 300,000 species of insects alone, there are, of course, plenty of spiders in Costa Rica – 2000 known species to be precise. 

The country may sound like an arachnophobes worst nightmare, but fortunately, the vast majority of spiders in Costa Rica pose no threat at all to humans. From hairy tarantulas to the Arrow-shaped micrathena, you may come across some pretty gruesome-looking spiders in Costa Rica, but most tend to keep themselves to themselves and steer clear of humans.

So which of Costa Rica’s many spiders do pose a threat to humans? Read on to discover five of the most dangerous spiders in Costa Rica.

Brown recluse spider

The brown recluse spider has long spindly legs and violin-style markings on its back.
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The brown recluse spider – aka the brown violin spider – has long spindly legs and violin-style markings on its back. They are largely nocturnal creatures, who – as their name suggests – like to hang out in isolated spots. Spinning their webs in disused structures such as sheds and lurking under woodpiles, keep an eye out for these creatures around dark and dank spaces.

While not typically aggressive, the recluse spiders have a reputation for biting in self-defense. They pack a nasty bite, which can cause vomiting, dizziness, and severe pain. The initial bite is very rarely felt as the spider’s fangs are so small, meaning that most victims do not seek medical attention once bitten. This is a mistake, as while not usually deadly, the wounds caused by these spiders can become infected if not treated and cause gaping wounds of 20cm across and 2 cm deep in the human body. Google what one of these wounds looks like, we dare you. 

Black widow

The female black widow spider is infamous for eating its partner as a post-coital snack.
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Did you know that there are three varieties of black widow spiders that are native to Costa Rica? These spiders are infamous for chowing down their partners after mating. They have shiny black bodies with distinctive red hourglass-shaped markings on the underside of their abdomens.

Male black widows are fairly innocuous, but female black widows can be very dangerous. With venom considered 15 times the strength of the venom of most rattlesnakes, you don’t want to end up on the receiving end of a black widow bite. Their venom contains neurotoxins, which attacks the nervous system of their prey. Bites from black widows have been known to cause paralysis of the diaphragm, leading to breathing difficulties, as well as a whole range of other side effects, such as dizziness, nausea, and even blackouts. While many people will only experience severe pain, others can react particularly badly and require urgent medical attention. Black widow bites are particularly dangerous, and indeed can be fatal, for young children, the elderly, and the infirm. Luckily, these spiders aren’t aggressive by nature. They’ll only attack when provoked, so if you spot one be sure to stay well away.

Brown widow

brown widow spider
Photo by Bernard DUPONT at Wikimedia

The brown widow spider is less striking in appearance than its black and red cousins. They usually have tan or brown bodies with black markings, and can also be recognized by the geometric markings on the underside of their abdomen.

They can be found in sheltered and isolated spots, such as garages and storage areas, where they like to make their homes away from human interference. Interestingly, although they are more poisonous than the black widow spider, a brown widow spider bite is less harmful. This is because brown widows inject less venom per bite than black widows. While their bite is still painful, it’s never fatal. And it’s only the ladies you have to watch out for –  males brown widows are not known to bite, much less be poisonous. 

Golden silk orb weaver

The golden silk orb-weaver is one of the largest spiders in Costa Rica
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With long banana-shaped abdomens and markings that sort of resemble a caper, Golden silk orb-weavers are remarkable-looking spiders. With females growing up to 3-inches long excluding their legs, they are also some of the largest species of spider in Costa Rica. Golden silk orb-weavers get their name from the golden sheen of their webs. Incredibly hard workers, these spiders can weave webs that reach 2 meters wide, the equivalent of 40-times the body length of the larger females. The fiber of their webs is also incredibly strong, with a tensile strength up to 8 times that of steel. This means they’ve been known to occasionally trap small birds and bats in their webs, which the spider wraps up and consumes.

Golden silk orb-weavers tend to hang out in swamps or shady woods. Luckily, while they look fearsome, this species of spider doesn’t pose too much of a risk to humans. While their venom is potent and neurotoxic, it’s not nearly as powerful as many of the other spiders on this list. The bite causes local pain, redness, and blisters that normally disappear within a day or so.

Brazilian wandering spider

The Brazilian wandering spider is one of the most toxic spiders in Costa Rica - and the world!
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Okay. We saved the most dangerous spider in Costa Rica until last: The Brazilian wandering spider. These large and intimidating arachnids are considered to be among the most venomous spiders in the world – and they’re certainly the most dangerous spiders in Costa Rica. Their scientific name, Phoneutria, which derives from the Greek word ‘murderess’, gives a clue into their nature. Brazilian wandering spiders take a more direct approach when it comes to hunting. Rather than spinning webs, they scuttle around on the forest floor at night, actively hunting insects, small amphibians, reptiles, and even mice, which they can kill in just one bite.

Also known as banana spiders, Brazilian wandering spiders tend to live amongst banana plants and have been known to sneak into shipments of bananas, leaving a nasty surprise for whoever ends up unpacking the boxes. You can recognize a Brazilian wandering spider by their large bodies, which grow to around 2 inches, and legs that span around 6 inches. The underside of their fangs is red to ward off predators, or unlucky humans who may have found themselves within close range. 

The Brazilian wandering spider possesses a deadly venom that can be fatal to humans, especially young children or the elderly. Causing severe pain, nausea, fever, blurred vision, high or low blood pressure, and convulsions, bites from Brazilian wandering spiders require immediate medical attention. If left untreated, they have the potential to be fatal. Thankfully, however, it’s rare for Brazilian wandering spiders to attack humans, and even when they do, they don’t tend to use all their venom in one bite.

Are there poisonous spiders in Costa Rica?

There are over 2,000 species of spider in Costa Rica, but only a handful are poisonous. These range from the Brazilian wandering spider, which is considered to be one of the world’s most toxic spiders, to black and brown widow spiders and the brown recluse spider. While all of these species possess toxic venom, fatality by spider bite in the country is extremely rare. Nonetheless, it’s important to remain vigilant and never get too close to any wacky-looking web spinners. 

What’s the biggest spider in Costa Rica? 

Female golden silk orb-weavers grow up to 3-inches long excluding their legs, making them among the largest spiders in Costa Rica. They are recognizable by their long banana-shaped abdomens and markings that sort of resemble a caper. But it’s likely you’ll see their webs before you see the spiders themselves! Golden silk orb-weavers weave golden-hued and incredibly strong webs that can reach 2 meters wide, the equivalent of 40-times the body length of the larger females. 

What’s the most common spider in Costa Rica?

The most common spider in Costa Rica is also one of the most harmless – the daddy long legs. These lanky spiders are prevalent in every continent in the world, bar Antarctica, meaning you’ll likely have seen them hanging around your home country.

There are plenty more animals to fear in Costa Rica than just spiders! Interested to know what other deadly animals call Costa Rica home? Check out our list of the 9 most frightening and dangerous animals in Costa Rica.