Redback Spiders - All you need to know!

Female redback spider with classic red markings

Female redback spider with classic red markings

The redback spider (Latrodectus hasselti) is found across Australia. Being common in urban areas it is one of the most frequent causes of spider bites. Control and prevention is relatively straightforward through a pest control spray treatment.

What do redback spiders look like?

Female redback spider

This is the redback most people are familiar with. Females are a shiny, black spider up to 3cm long, with an obvious red/orange stripe on the upper side of the abdomen and an hourglass mark on the underside of the abdomen. However, there can be colour variations – their colour may vary from black to brownish and sometimes the red stripe can be broken.

A females redback can live for 2-3 years and produce up to 10 egg sacs during her lifetime, each containing around 250 eggs – a redback infestation can quickly get out of control!

Male redback spider

The male redback is many times smaller than the female. The body is a light brown colour with white markings on the upper side of the abdomen and a pale hour-glass marking on the underside. The red marking are often not as obvious as those on the female.

Males do not build webs and will go searching for a female to mate. The male goes through an elaborate mating process to see whether the female is ready to mate. If he gets this wrong the female will mistake him for prey and eat him! Even if she accepts his mating display and is prepared to mate, as part of the mating process the male offers his abdomen towards her mouthparts to divert her attention during the process. The female then starts to eat the male’s abdomen during mating! Not surprisingly, most males die as a result.

Baby redback spider

Young redback spiders, even the females, will have a more mottled colouration, often with additional white markings on the abdomen. These young spiderlings are cannibalistic and will eat egg sacs and other redback spiderlings. Males will mature in around 3 months and females in around 4 months.

Female and male redback spiders in web

Female and male redback spiders in web

Where do redback spiders live?

They generally like dry sheltered spots to build their webs. Around the home these are the key hiding places

  • In sheds and pergolas

  • Under the outdoor furniture / BBQ

  • Along fencing

  • Inside tubular fencing

  • Under rocks, wood piles and stored goods

  • In the sub-floor

  • In the roof void, especially near down lights

Redback spider web

Redback spider webs are not a classic spider web and may be a bit hard to spot. The web looks a bit like an untidy fishing net, often with leaves or debris included. Sometimes an egg sac can be spotted in the web.

Red back spider bite

Redback spider venom

The redback venom is a neurotoxin that works directly on the nerves. An antivenom has been available since 1956.

Redback bite symptoms

The redback spider bite is painful and the pain increases rapidly, progressing up the affected limb and lasting at least 24 hours. Other symptoms include sweating (also local sweating at bite location), nausea and vomiting. No deaths have occurred since the antivenom has become available.

Red back spider bite treatment

Follow the 5 step spider bite first aid:

  1. The patient should sit down and try to relax

  2. Clean the bite with water and disinfectant

  3. Apply an ice pack to the bite area

  4. If possible, collect the spider for identification

  5. See medical attention

DO NOT apply a pressure bandage, as this worsens the pain and does little to stop venom movement (as it is slow moving anyway).

Red back spider treatment

A general insecticide spray treatment around the perimeter of the home and likely redback hiding places once or twice a year will keep redbacks at bay. Any spider present will be killed directly by the spray and good products will leave a thin layer of insecticide on treated surfaces, to prevent other redback spiders moving in.

Make sure the treatment is thorough, to get into the cracks and crevices. For example, spray up the inside of each pole of tubular fencing.

In areas more exposed to rain and sun, two applications a year is recommended.

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