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Native to Australia, the redback spider, also known as the Black Australian widow, is a highly venomous specie. Believed to originate from South Australia as well as the neighbouring Western Aussie desserts, it is now spread throughout Australia, Southeast Asia and New Zealand. The area is quite large for such a dangerous little pilferer.

The reason why these comb-footed spiders are so dreaded, is due to their poisonous trait and the liking to live near people in more urban areas. In regions where human activity is quite high, an increase in insects is more likely too. This makes our environment the perfect hunting ground for redback spiders.

Appearance and habits

Redbacks are bilaterally symmetrical and cold blooded. Females inherently have a prominent reddish-orange dorsal stripe, which may appear broken, on the upper abdomen and a red hourglass shaped spot on the ventral side of their pea shaped bodies. The adults are jet black, while the juveniles are slightly brown in colour with no distinctive white markings. Once the female becomes older, she loses the extra white markings formed on her abdomen. They are approximately 10mm long while the smaller male only stretches between 3mm and 4mm in length. Males are typically lighter brown in colour with the same reddish dorsal stripe and a paler hourglass shaped body. Both are similar to those of the female, but not as defined. The white markings on the male’s abdomen remains intact as they get older, unlike the females. Both have delicate, willowy legs and are venomous. However, only the female bite is dangerous and deadly.

Redback spiders are found throughout Australia. Where ever there is sufficient food and water supply, shelter and warm enough temperatures for breeding, that is where you will find them.

They lure their entangled preys to their web, where their venom will kill them. Only one single toxin, within the dense venom compound, is responsible for the death of the defeated. This is called, alpha- latrotoxin.

Like most insects and other animals, they only defend themselves and attack when being disturbed and aggravated. When the redback’s web is ruffled, they may only inject their venom if they feel threatened. Else a warning bite is sufficient.

Redbacks are notorious and nocturnal. Females often camouflage themselves during the day, while active during the night, spinning their web. Very much like lonely spinsters, as they remain in the same setting most of their life.

Almost any small unlucky insect, entangled in the spider’s web, will be eaten. Smaller ones, like mice, lizards and snakes are also known to be prey to these back stabbing spiders.


Symptoms that occur after a spider bite, includes swelling of the area, pain that progresses from the bite site, nausea, vomiting, sweating, muscular weakness, headaches, abdominal or even chest pain and increased blood pressure.

If it happens that you do get bitten, don’t panic. Make sure someone is available to monitor you when possibly developing symptoms. Do not apply a pressure bandage, but rather an ice pack. It would be advisable to seek medical attention, especially if you are in the higher risk bracket with heart issues, may be pregnant, with infants and young children, are elderly or suffer from any other severe illness. If necessary, an antivenom will be injected.

Remember to take the dead spider with you to identify it at the hospital, if need be.

What we can do to live safer where spiders occur

Redbacks create their webs where the area is dark, less visible and more sheltered and dryer. Be vigilant around your home during warmer summer months, especially when reaching into darker areas, under the floorboards, in the roof and your mailbox.

These spiders can be found in gardens, in wood piles, on verandas, inside buildings, within outdoor furniture – literally almost anywhere.

Weird and brutal sex lives, lies and redback tape

The males elude sexual cannibalism, by mating with immature females who are too young to eat them after mating. This also gives them a chance at mating more than once. How clever is that? This Is referred to as a fitness enhancing tactic. They are also known to slow down the mating process, by somersaulting their abdomens straight into the jaws of the female while copulating. It gives the female something to chew on while it gives the male a better chance at paternity.

Redbacks can breed anytime during the year, but it is more likely during the warmer summer months. The females may store their sperm for up to two years in order to fertilize their eggs, but lay eggs in-between from different sperm supplies. The eggs are dispersed in their web where they change colour.

An interesting fact is that the males spend up to two hours of courtship before mating, by sending vibratory signals along the web to the female. They don’t however send any signals to the immature females. The longer time they spend on the courtship ritual, the less likely it is to be cannibalised.

The dangers of funnel web spiders

Atracidae, commonly known as funnel web spiders, are dangerous and native to Australia. The Sydney tunnel web spider is possibly the most deadly.

Their name says it all. They spin their webs into a funnel shaped T or Y and bury themselves deep inside. When their prey approaches with curiosity they fall inside and are trapped. The spider will sink its fangs deep into their prey releasing venom that ultimately kills the cockroach, lizard, snail or millipede. Gone and defeated after several clingy and desperate bites.

The front of their bodies is hairless, making them appear larger and scarier looking than their 1 to 5cm lengthiness, while the females are stockier. Their fangs are large and point downwards toward the floor and not to each other like many other spider species. They are strong, powerful and connected to many venom glands. Their bites are painful due to the larger fangs which can be bigger than a brown snake.

The Sydney funnel web spider is one of the most dangerous in Australia. In most spider families the females are usually the ones carrying the venomous poison, but in the Australian funnel web spider, the male takes the lead with up to six times more venom.

Why is this so dangerously deadly?

The venom contains a substance, neurotoxin atracotoxin, which targets the nervous system instantly and eventually attacks the vital organs in the body.


Once bitten by Sydney’s most dangerous spider, it is crucial to seek medical attention immediately. The venom spreads fast and waiting a few hours is not advised. Until you receive medical assistance with anti-venom, apply firm pressure to the affected area in order to prevent the venom spreading faster, moving into the bloodstream and the rest of the body.

It is always ideal to take the spider with you to hospital in order to determine what treatment is required for which spider bite, as some are more lethal than others.

The difference between the two spiders:

In most spider species, the female is the predominant lethal attacker where venom is concerned. Unlike the Redback spider, the highly venomous male Australian funnel web spider, carries more potent venom than the female. The males are roaming loners, while the females live in colonies of up to 100 other counterparts.

Should I kill a spider?

We strongly advise not to kill any spider. Afterall, you might just aggravate the creepy and get bitten.

Leave the spider section to the professionals who know exactly what they are doing without disturbing the spider colony or being attacked and bitten. Call Sydney’s best Pest Control on 1300 760 045 to determine what spider specie has invaded your home, which treatment to continue with and what can be done to prevent future pest invasion.

Spiders form part of our eco system and are needed to clear out other pests. It is important not to just kill them because they are a nuisance, but consult a professional who can guide you with the correct treatment option. Not all spiders are treated for in the same manner.

Further informative reading

Spider control

What spiders are in Sydney?

Are redback spiders increasing in Sydney?

Spiders in Sydney and how to treat them