What is the Brazilian wandering spider: Is it really that dangerous?

The Brazilian wandering spider is a species group of large, nocturnal spiders belonging to the genus Phoneutria. The name “wandering” refers to their behaviour of actively roaming the forest floor at night rather than building webs. These spiders are often cited as among the most venomous spiders in the world. The most well-known species include Phoneutria fera, Phoneutria nigriventer, and Phoneutria keyserlingi.

Do Brazilian wandering spiders really come from Brazil?

The Brazilian wandering spider is native to Brazil. However, its distribution extends beyond Brazil. These spiders are also found in other parts of South and Central America, including Colombia, Ecuador, Peru, Venezuela, Bolivia, and parts of Central America. Despite the wide range, the name Brazilian wandering spider is used because the first species were described in Brazil and the country remains a core part of their habitat.

In Brazil, the local name for the Brazilian wandering spider is "aranha armadeira", which translates to "armed spider" in Portuguese. This name refers to the spider's defensive posture, where it raises its front legs when threatened, appearing as if ready to strike.

Where to find the Brazilian wandering spider in Brazil

In Brazil, the Brazilian wandering spider is commonly found in the Atlantic Forest region, particularly in the southeastern states such as São Paulo, Minas Gerais, Rio de Janeiro ,and Espírito Santo. They inhabit both rural and urban environments. These spiders are often encountered in banana plantations, which is why they are sometimes referred to as "banana spiders" - though the term "banana spider" is not specific and is sometimes also used to refer to different species, depending on the region.

It is not uncommon for them to hide in boxes of fruit or other shipments, leading to accidental export to other countries. The spiders tend to hide during the day under logs, rocks, or in crevices. At night, they come out to hunt. Urban encounters typically happen when the spiders seek shelter in shoes, clothing, or household spaces such as garages or basements.

Brazilian wandering spider bites

Brazilian wandering spider bites are rarely fatal. When bites occur, they are usually the result of accidental contact when the spider is disturbed. The species Phoneutria nigriventer is the most commonly involved in human bites in Brazil.

The venom contains a complex mix of neurotoxins. The primary component responsible for its effects is known as PhTx3, a class of peptide toxins that interfere with calcium ion channels in nerve and muscle cells. Envenomation symptoms in humans may include local pain, swelling, sweating, nausea, elevated heart rate, and in some cases, systemic effects such as respiratory distress or high blood pressure.

One of the more unusual symptoms reported in males is priapism, a prolonged and painful erection, which has led to interest in the venom's biochemical properties for potential medical applications.

Most bites, however, do not involve the injection of a full dose of venom. Like many venomous animals, Brazilian wandering spiders may deliver dry bites, especially in defensive situations. This means the spider may bite without injecting venom, reducing the risk of severe symptoms.

Fatalities from Brazilian wandering spider bites are extremely rare. In cases where antivenom is administered promptly and supportive care is given, recovery is usually complete. Brazil has an effective antivenom production and distribution system which reduces the risk of death from spider envenomation.

How dangerous is the Brazilian wandering spider really?

Photo: Paraná State Govt., Brazil

While the Brazilian wandering spider has a highly potent venom in laboratory tests, the danger it poses to humans in real-world situations is less severe than often portrayed.

In Brazil, where the wandering spiders are native, there are approximately 4,600 bite cases per year, making this genus the second most frequent cause of spider bites in Brazil. Despite this, deaths from bites are rare. Most documented cases involve only mild (almost 90%) to moderate (8.5%) symptoms, according to one study. Children and individuals with underlying health conditions may be more vulnerable to complications.

You can read the official Brazilian government report on spider bite data in the Sistema de Informação de Agravos de Notificação (SINAN), which is managed by the Ministry of Health. The system provides yearly statistics on envenomation incidents, including those involving Phoneutria species. SINAN includes breakdowns by species, region, age group, severity, and trends over time.

How to identify the Brazilian wandering spider

The Brazilian wandering spider can be identified by its size, colouring, and behaviour. Adult spiders typically have a leg span of up to 15 centimetres and a body length of around 5 centimetres. Colouration varies by species but generally includes a mix of brown and black with some red or orange markings on the undersides of the legs in certain species.

Due to similarities with other large spiders in South America, including tarantulas and huntsman spiders, professional identification may be required in cases of suspected envenomation. Specimens brought to hospitals can be analysed for proper classification.

Why the Brazilian wandering spider became famous – and other interesting spiders in Brazil

The Brazilian wandering spider gained international fame in part due to its inclusion in the Guinness World Records as the most venomous spider. Its reputation was further amplified by media reports of the spider being found in supermarket bananas exported from South America to Europe and North America. These stories often included claims of aggressive behaviour and potential fatalities, which contributed to the spider’s notoriety. However, such reports tend to exaggerate the risk of the Brazilian wandering spider.

Brazil is also home to many other interesting spider species, including:

• Golden silk orb-weaver (Trichonephila clavipes) – Found in the Atlantic Forest regions of Bahia, Espírito Santo, and Rio de Janeiro. Builds massive golden-coloured webs that can span over a metre across and are strong enough to trap small birds or bats.

• Brazilian salmon pink tarantula (Lasiodora parahybana) – Native to the state of Paraíba, especially around Campina Grande in the Pantanal. Grows to a leg span of over 25 cm, making it one of the largest tarantulas in the world. It is often kept in captivity due to its size.

• Brazilian whiteknee tarantula (Acanthoscurria geniculata) – Found in the Amazon region, especially in Amazonas state near Manaus. Recognisable by the white stripes on its legs, it uses urticating hairs as a defence mechanism when threatened.

• Amazon orb-weaver (Parawixia bistriata) – Found in Acre, Rondônia, and other parts of the Amazon Basin. Lives in colonies and builds group webs in the evening but disassembles them at dawn to avoid predators.

• Spiny orb-weaver (Micrathena spp.) – Common in São Paulo, Minas Gerais, and Paraná, particularly in forested areas. Has spiked, armour-like abdomens that make them look like miniature crabs or thorns to deter predators.

• Cupiennius salei – Found in Pernambuco, especially around Recife in forested and coastal areas. Sometimes confused with the dangerous Phoneutria, but it is harmless to humans and known for its speed and night hunting.

• Ant-mimicking spider (Castianeira spp.) – Seen in Goiás, Distrito Federal, and parts of São Paulo. Mimics both the body shape and movement of ants to avoid predators and sometimes to approach ant prey undetected.

• Lynx spider (Peucetia spp.) – Common in the Cerrado regions of Goiás and Mato Grosso do Sul, often on flowering plants. Hunts during the day using excellent eyesight and can leap several times its body length to catch prey.

• Fishing spider (Trechalea spp.) – Found near rivers and streams in Amazonas and Pará. Can walk on water using surface tension and detects prey by sensing vibrations from insects and small fish.

More resources for planning your trip to Brazil

• Find cheap bus, ferry, and private transfer tickets on Bookaway, where you can make reservations ahead of time from abroad. Or, rent a car and give yourself the freedom to explore at your own pace.

• Find your perfect accommodation on Booking.com, with thousands of options ranging from luxury hotels to budget-friendly backpacker hostels

• You're not ready to travel until you have travel insurance. I recommend Safety Wing to my friends, family, and anyone travelling internationally. Get a free quote

• Forgetting something? Read my packing check-list for Brazil, and my list of 10 things you should do before you travel to Brazil