The World’s Most Venomous Spider

Written by AZ Animals Staff
Published: June 27, 2021
Written by AZ Animals Staff
Published: June 27, 2021


“Sydney Funnel-Web Spider is in competition with the Brazilian wandering spider as the world’s most venomous spider to humans.

Just about all spiders are venomous. Venom is how they subdue and partially digest their prey. Most spider venom isn’t that harmful to humans, but there are a few spiders out there whose venom can make a human being very sick or even kill them. The worst of these is, according to many scientists, the Sydney funnel-web spider, which is the world’s most venomous spider. Fortunately, this beast is only found in Australia and only within a 99-mile radius of Sydney, giving it its name.

Sydney Funnel-Web Spider Facts

  • The male is six times more venomous than the female.
  • They can stay underwater for as long as 24 hours thanks to the ability of their abdominal hairs to trap air bubbles.
  • Their silk is used to make optical instruments.
  • A funnel-web spider needs to be milked about 70 times to produce a dose of antivenin.
  • Though the venom of this little beast can be fatal to humans, it doesn’t much affect non-primate mammals.

Sydney Funnel-Web Spider Scientific Name

The funnel-web spider’s scientific name is Atrax robustus. Atrax is from Latin and means “dull black” or “dark.” Robustus means “strong” or “sturdy.”

Most Venomous Spider: Sydney Funnel-Web Spider Appearance

The Sydney funnel-web spider’s body is 0.4 to 2 inches long, with 2.36 to 2.75 inch long legs. It is glossy blue-black, black or brown. The head and the middle section of the body, or thorax are shiny and hairless, but the abdomen is covered with fine hairs. The spinnerets that produce silk are found at the end of the abdomen and are unusually long.

Males are smaller than females, but their legs are longer. They can also be told from females through their pedipalps. These are a pair of structures next to the spider’s jaws and right before their first pair of legs. In the male, the ends of the pedipalps have bulbs to transfer sperm. They also have a spur on each second leg that helps hold the female still while mating.

The fangs of this spider are huge. They are longer than the fangs of some snakes and can penetrate shoe leather.

Most Venomous Spider
Sydney Funnel-Web Spider sitting on a tree stump. The Sidney Funnel-Web Spider has fangs longer than some snakes!

Sydney Funnel-Web Spider Behavior

Atrax robustus lives in funnel-shaped burrows line with its silk, which gives the animal the other part of its name. They are usually solitary, though females have been found in colonies of conspecifics. Still, females don’t wander from their burrows unless they’re forced to do so. Males, on the other hand, wander about looking for females. They find them by detecting the pheromones on the trip lines of their webs.

The spider is nocturnal because that time of the day tends to be cooler and more humid.

When Atrax robustus is threatened, it will throw up its front legs and display its fangs in a threat posture. If the annoyance doesn’t go away, it will grab on to it and bite over and over, envenomating it. Another characteristic that makes this spider so dangerous is that it is aggressive and doesn’t prefer to run away and hide like other spiders. It also gives fewer “dry bites” than other spiders. Dry bites are those that contain no venom.

Most Venomous Spider: Sydney Funnel-Web Spider Habitat

Generally, Atrax robustus prefers places that are cool, moist, and dark, so they can be found beneath rocks, foliage, fallen, rotting logs, the soil of crawl spaces, and even in compost piles. Their burrows may be tunnels or funnels, with trap doors or one or two openings shaped like a T or a Y. These structures are between 7.9 and 23.6 inches long. The spider also lays trip lines at the entrance of its burrow. When prey wanders over these trip lines, the spider rushes out, grabs it, bites it repeatedly then takes it inside its funnel to eat.

Most Venomous Spider: Sydney Funnel-Web Spider Diet

The Sydney funnel-web spider eats insects, snails, millipedes, small vertebrates such as tiny lizards, and the occasional frog.

Most Venomous Spider: Sydney Funnel-Web Spider Predators and Threats

A person would think that this formidable creature must be an apex predator with nothing willing to take it on, but this isn’t true. As discussed, its venom affects different animals differently, and some animals have no problem hunting and eating it. Among them are centipedes, which will actually go into the burrows to get them. Other predators include pet cats and dogs, dingos, birds, and large reptiles that don’t react to the spider’s venom. Rats also hunt Atrax robustus. Interestingly, mice and guinea pigs, like primates, are badly affected by the venom.

Most Venomous Spider
The world’s most venomous spider, the Sydney Funnel-Web Spider, in defensive stance.

What eats the Sydney Funnel-Web Spider?

Animals that routinely and safely eat the Sydney funnel-web spider include cats and dogs, including dingos, monitor lizards, geckos, rats, and marsupials such as dunnarts.

What does the Sydney Funnel-Web Spider eat?

It eats cockroaches, flies and other insects. It also eats smaller lizards and frogs.

Sydney Funnel-Web Spider Reproduction and Life Cycle

Males become reproductively mature when they’re about four years old, and that’s when they go looking for females. First, he’ll weave a little mat of silk and add sperm to it, then transfer the sperm to his specially modified pedipalps. When he finds a female there is often some threat displaying on the part of both of them until she accepts him. Then, he immobilizes her by grabbing her second legs. He uses his palps to insert the sperm into the female’s genitalia then leaves in a hurry.

After this, she’ll spin an egg sac and deposit about 100 greenish-yellow eggs into it. In the three weeks they take to hatch, she’ll clean and turn the egg sac and defend it. When they hatch, the spiderlings will stay with her until they’ve molted, or shed their exoskeleton twice. Then, they’ll leave to dig their own burrows.

Most Venomous Spider: Sydney Funnel-Web Spider Population

Though scientists don’t know exactly how many Sydney Funnel-web spiders exist in the wild, the animal has no special status under the IUCN Red List. There are about 1000 who live at the Australian Reptile Park.

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FAQs (Frequently Asked Questions) 

What is a Sydney Funnel Web Spider?

The Sydney funnel-web spider, Atrax robustus is a type of spider called a mygalomorph. This is an infraorder that includes tarantulas and mouse spiders. These spiders usually have robust bodies and jaws that point downwards. The Sydney funnel-web spider is one of 40 species of funnel-web spider. It is notorious for its aggression and its venom, which can kill a human being if they’re not treated promptly.

Why is the Sydney Funnel Web Spider so dangerous to humans?

Scientists believe that the lethality of the male’s venom is an accident. Clearly, humans and primates aren’t the prey of this small animal, but humans have been known to eat spiders, and the male’s venom developed to deter predators. It is the male who leaves his burrow to wander around in search of females and makes himself vulnerable to predation. Ironically, the animals who regularly eat the spider, such as rats and geckos, are not much affected by the venom.

How long does a Sydney Funnel Web Spider live?

Males live from six to nine months after they’ve reached sexual maturity, but females can live for over a decade.

Why are Sydney Funnel Web Spiders found in Sydney, Australia?

Atrax robustus was in that part of the continent well before the city was founded. It is more accurate to ask why did people raise the city of Sydney, Australia in the habitat of such a venomous animal. (The answer is that Great Britain decided to establish a colony at Sydney Cove in 1788).

Why does the Sydney Funnel Web Spider’s venom affect people so badly?

The venom is as dangerous as it is because it contains a toxin called Robustoxin which attacks the nervous system. The bite itself is painful due to the size of the animal’s fangs and its penchant for biting repeatedly until it is pulled off. Fortunately, there is an antivenom.