Redback spiders are found throughout Australia, in many habitats, including urban areas. They often hide in dry, sheltered places such as garden sheds, mailboxes and under toilet seats.
Numbers of redback spider bites are uncertain, but about 2000 are reported each year and about 250 people receive antivenom. No deaths have been recorded since redback antivenom became available in the 1950s.
Most serious bites are from the female redback spider, which measures about 1cm long (bigger than males) and is recognisable by the well-known red stripe on its back, from which it gains its name. Their venom affects the nervous system, which is potentially dangerous for humans, but their small fangs make many of the bites ineffective. Envenomation can cause various effects, but the main symptom is severe and persistent pain – which can last hours to days depending on the person’s sensitivity to the venom – and may include nausea, malaise and lethargy.
Cupboard spiders (Steatoda sp.) are often mistaken for redbacks and they produce similar symptoms, though their venom is less potent. Redback venom is effective against these bites.