The Redback Spider - Latrodectus hasselti
Redbacks are Australia's best-known spider. They appear in songs and even have a beer named after them. Redbacks live all over Australia but are less common in colder regions like Tasmania. They thrive in populated areas. Hundreds of bites are reported each year but less than 30 percent require antivenom treatment. Only female Redbacks usually bite people - the males are generally too small.
They belong to the Family Theridiidae, which is found worldwide. The notorious Black Widow Spider (Latrodectus sp) of the United States is a close relative of the Redback Spider, and only differs in appearance by the absence of a red dorsal stripe. Other species of Latrodectus occur in the Africa Pacific Islands, New Zealand, Europe and North and South America.
Insects are the usual prey of Redback Spiders, but they are capable of capturing quite large animals, such as male trapdoor spiders, king crickets and small lizards, if they become entangled in the web. Prey-stealing is also common, with large females taking stored food items from others' webs.
Redback bites occur frequently, particularly over the summer months. More than 250 cases receive antivenom each year, with several milder envenomations probably going unreported. Only the female bite is dangerous. They can cause serious illness and have caused deaths. However, since Redback Spiders rarely leave their webs, humans are not likely to be bitten unless a body part such as a hand is put directly into the web, and because of their small jaws many bites are ineffective. The venom acts directly on the nerves, resulting in release and subsequent depletion of neurotransmitters.
Common early symptoms are pain (which can become severe), sweating (always including local sweating at bite site), muscular weakness, nausea and vomiting. Antivenom is available. No deaths have occurred since its introduction.