10 Most Dangerous Spiders in the World

5. Six-eyed Sand Spider (Sicarius hahni)

Six-eyed sand spider

Six eyed sand spider (Sicarius) Photo: Beliar spider / License

What’s got eight legs, six eyes and lives in the deserts of Southern Africa?! That’s right, the six-eyed sand spider.

The scientific name for this spider’s family is Sicarius which means ‘murderer’ and the spider is certainly an assassin. It hunts by burying itself in the sand and waiting for its unsuspecting victim to wander by at which point it pounces. In trials it was shown that the venom from a bite was fatal to rabbits in as little as 5 hours.

Like their close relatives, the recluse spiders, the venom of the six-eyed sand spider is a powerful cytotoxin. In the case of Sicarius the venom is both hemolytic and necrotic meaning it causes blood vessels to leak and destruction of  flesh.

But how dangerous is this spider to humans? Well we aren’t quite sure; there have only ever been two suspected cases of bites to humans and neither were conclusively attributed to the six-eye. Combined with the fact it can survive for a year on one meal it probably isn’t the biggest threat to humans.

4. Redback / Black Widow Spider (Latrodectus)

Redback Spider

Photo: © Laurence Grayson

The black widow spider, or redback as it is known in Australia is one of the most iconic spiders on the planet. Instantly recognisable by its round black abdomen with striking red markings these are definitely spiders not to be trifled with. Both the redback and the black widow are from the Latrodectus family with the redback being marginally more venomous than the black widow. And that venom is potent, more so than any other spider but one. The only reason these spiders don’t top the list is because they are smaller and deliver less of it.

The effects of this lethal toxin range from burning pain to a systemic condition known as latrodectism. Symptoms include general pain and swelling spreading from the affected area, abdominal cramps, nausea and sweating to name a few. This condition occurs in around half of bites and was often fatal in the very old and young before anti venom became available.

3. Brown Recluse / Chilean Recluse (Loxosceles)

Brown Recluse - Loxosceles

© Steve Collender

The recluse spiders occur in warmer climes throughout the world. Also known as violin spiders, fiddle-backs or even reapers these six-eyed spiders all possess tissue destroying venom and belong to the Loxosceles family.

Recluse spiders have garnered quite a reputation for themselves over recent years and the internet is awash with some pretty ugly photos of the effects of their bite. The venom of this group of spiders is known to be necrotic, i.e. flesh-eating and whilst usually mild, can result in a condition known as Loxoscelism. In these severe cases the area around the bite begins to die and a deep open sore is formed. There is no effective treatment for these bite wounds and they may take months to heal, sometimes requiring skin grafts.
In the very worse cases limbs have needed to be amputated and there have been a significant number of fatal bites, particularly from the Chilean recluse.

On a more positive note, the recluse is so called as it is relatively shy and not regarded as aggressive. Their small fangs also make it less likely they will deliver a significant dose of venom.
However, think twice before spraying them with a dose of bug-killer; it is reported that they are immune to some insecticides and only make them more toxic and angry!

2. Sydney funnel web (Atrax robustus)

Sydney funnel-web spider

Sydney funnel-web spider

The Sydney funnel-web spider (Atrax robustus)  is a veritable bruiser amongst the spider world. Whilst most spiders seek to avoid confrontation with humans the funnel-web will charge in delivering a volley of bites whilst clinging to its victim. So although its venom is no more potent than many of the spiders on this list, the funnel-web makes sure the unfortunate recipient gets the full dose.

In addition to its temperament the Sydney funnel-web is well equipped for the job. It has the most impressive fangs of any spider; these needle sharp weapons are longer than those of some snakes. Armed with these killer fangs and powerfully built, the funnel web is reputed to be able to bite through shoe leather and even finger nails.

Unlike virtually every other group of spiders it is the male Sydney funnel-web that is equipped with the most potent venom – up to six times stronger than that of the female. The venom itself is a neurotoxin which appears to be particularly effective against primates. Within minutes of being bitten the victim may suffer extreme symptoms such as muscle spasms, palpitations, vomiting, confusion and swelling of the brain. In some cases death has followed in as little as 15 minutes after the bite occurred.

The good news is an effective anti-venom was introduced in 1981 and there hasn’t been a death since.

1. Brazilian Wandering Spider (Phoneutria)

Brazilian wandering spider

Brazilian wandering spider (Phoneutria sp.) Photo: Geoff Gallice / License

When a spider’s scientific name is derived from the Greek for murderess (Phoneutria) you can guess it’s going to be trouble and this is certainly the case for the wandering spiders. According to Guinness World Records the Brazilian wandering spider (Phoneutria fera) is officially the world’s most venomous spider. It is capable of injecting a powerful neurotoxin which is nearly 20 times more deadly that that of the Black Widow spider if it gets into the blood stream. That is as potent as the venom of many deadly snake species and the effects are similar. The symptoms of envenomation include a loss of muscle control leading to breathing problems which can result in complete respiratory paralysis and eventually asphyxiation.
But there are two other major side effects to the wandering spider’s bite; firstly there is intense pain and secondly, if you happen to be male there is the four hour hard on. Yes, you did read that correctly – the bite of the Brazilian wandering spider can cause an erection that lasts for several hours, unfortunately it is also painful.

In addition to the this deadly venom the behaviour of the wandering spider make it particularly dangerous to humans. As its name suggests the spiders are not confined to a web in a dark corner. In fact they like to turn up in all manner of hiding places; boots, piles of clothes, log piles, cars and bunches of bananas. Also known as ‘banana spiders’ wandering spiders have been known to hitch a ride across the globe in boxes of bananas. In one case a man in the UK was bitten after buying bananas in his local supermarket.

There is little doubt that these are dangerous spiders. Their aggressive nature and close contact with humans have resulted in a number of deaths over the years. In one tragic case a single spider was responsible for the deaths of two children in São Paulo. Fortunately an effective antivenom has been developed and there have been relatively few fatalities since.