Your Guide to the Redback Spider

Redback spiders are found throughout Australia.

They are renowned for a couple of reasons: they have a distinctive red stripe on the back of their abdomen, and they like living close to human habitation.

Redback spiders also have a fearsome reputation as one of our country’s deadliest spiders, as their bites have killed people in the past.

But are they still deserving of this reputation? Let’s take a closer look.?

Appearance

Male and female Redback spiders look vastly different from each other.?

Female Redback spiders are generally dark brownish to black in colour, and they have an orange to red stripe running lengthways across the top of their abdomen. On the underside of their abdomen, meanwhile, they have an hourglass shaped marking that is also orange to red in colour. Their body is approximately the size of a large pea, and it is at odds with their skinny legs.

On the other hand, male Redback spiders are generally light brown in colour, and the markings on the top and underside of their abdomen tend to be pale or white.?

Habitat

Given they like to build their webs in dry, sheltered sites, Redback spiders generally live close to human habitation – for instance, in toilets, sheds, and junk piles.

They use their webs to feed on insects and any other prey that gets trapped, including male Trapdoor spiders, king crickets, and small lizards.?

Danger to Humans

Redback spiders are generally retiring creatures and only bite in defence.

Most bites occur when the spider comes into direct contact with human skin – for instance, when a hand enters their web, or when they are sat or stood on. ?

In any case, only a bite from a female Redback spider has the potentially to cause danger. At 3 millimetres in diameter, male Redback spiders are so small that their fangs cannot penetrate human skin.

Female Redback spiders also have small jaws, which means that less than 20% of bites result in significant envenomation.?

Bite

Redback spider venom attacks the nervous system and causes the release and subsequent depletion of neurotransmitters – chemical messengers that transmit information between neurons, or from neurons to muscles.

The signs and symptoms of a Redback spider bite are highly variable, but can include:

• Intense burning pain at the bite site.
• Redness, swelling, and sweating around the bite site.
• Nausea, vomiting, and abdominal pain.
• Tenderness in the armpit or groin of the affected limb.
• Loss of coordination.

Rapid, shallowing breathing.?Redback spider bites have been fatal in the past – however, no deaths have been recorded since the introduction of antivenom in 1959.

And though over 250 cases of Redback spider bites receive antivenom each year, it is estimated that several other cases go unreported due to the mildness of the symptoms.?

First Aid

1. Reassure the casualty and keep them under constant observation.
2. Apply a cold compress to the bite site for periods of up to 20 minutes to lessen the pain.
3. If the casualty is a young child (under 8 years), a pregnant woman, or if they exhibit any signs of deterioration, call Triple Zero (000) for an ambulance.
4. DO NOT?use?the?Pressure Immobilisation Technique, as the venom moves slowly and this will just worsen the pain.

Anaphylaxis

Some people can have a severe allergic reaction to a spider bite. This is called?anaphylaxis, a condition that can be fatal in as little as 15 minutes. Symptoms include:

• Swelling in the tongue, throat, or face.
• Difficulty or noisy breathing.
• Hoarse voice or difficulty speaking.
• A wheeze or persistent cough.
• Dizziness, collapse, or falling unconscious.
• Becoming pale or floppy (young children).
• Abdominal pain, nausea, or vomiting.
• Hives, welts, or body redness.
• Anxiety or a sense of doom.

If the casualty begins exhibiting any of the above symptoms, call Triple Zero (000) for an ambulance, consult the Australian Resuscitation Council's?anaphylaxis treatment guideline, and follow?DRSABCD?and prepare to perform CPR.

Final thoughts

Redback spiders are common throughout urban areas in Australia.

Though they have a fearsome look and reputation, Redback spiders are generally retiring creatures and only bite in defence.

Likewise, most people who sustain a Redback spider bite only experience mild symptoms like pain, swelling, and nausea.

As such, most Redback spider bites can be remedied with a cold compress – however, if the casualty is young, pregnant, or begins showing signs of deterioration or anaphylaxis, seek medical attention immediately.

It is also worthwhile noting, no deaths from a Redback spider bite have been recorded since the introduction of antivenom in 1959. So as long as you remain calm and use your first aid knowledge and skills to respond to the casualty’s condition, you will have the best chance of a positive outcome.?

To learn even more about identifying and treating bites from some of Australia's deadliest spiders, check out the following article in our Resource Library, and book a First Aid course today!