Australia is known for its distinctive wildlife, including numerous spider species. While many spiders are venomous, the common assumption that all are dangerous to humans is not accurate. Only a limited number pose a serious health risk.
Defining Venomous Spiders in Australia
Nearly all spiders are venomous, using venom to subdue prey. However, not every venomous spider poses a threat to humans. The distinction is between being “venomous” and “medically significant,” meaning their venom can cause considerable harm. Australia hosts an estimated 10,000 spider species, though only about 3,600 to 4,000 are formally described, and only a small fraction are medically significant. Historically, spider bites led to fatalities, but due to advancements in medical treatment and antivenom availability, no spider bite deaths have been recorded since 1979. Severe outcomes from spider bites are now exceedingly rare.
Australia’s Key Medically Significant Spiders
Among Australia’s diverse spider population, a few species are recognized for their medically significant venom. These include Funnel-web spiders (particularly the Sydney Funnel-web), Redback spiders, and Mouse spiders.
Sydney Funnel-web spider
The Sydney Funnel-web spider (Atrax robustus) is a highly venomous, glossy, dark species measuring 1.5 to 3.5 centimeters long, often considered one of the world’s most dangerous spiders. They are primarily found within a 100 to 160-kilometer radius of Sydney, living in burrows under logs, rocks, and in humid, sheltered areas, often entering suburban gardens. The male’s venom is potent, containing a neurotoxin that can cause severe illness or death if untreated. Symptoms include intense pain, sweating, nausea, vomiting, muscle twitching, breathing difficulties, and elevated blood pressure. While 13 deaths were recorded before antivenom became available in 1981, there have been no fatalities since its introduction, despite 30 to 40 bites reported annually.
Redback spiders
Redback spiders (Latrodectus hasselti) are found across Australia. Females are identified by their black body with a prominent orange to red stripe on the upper abdomen and an “hourglass” marking underneath. Females are about 1 centimeter long, while males are significantly smaller. These spiders prefer dry, sheltered locations near human habitation, such as sheds and mailboxes. Their neurotoxic venom causes severe local pain that can spread, along with sweating, muscle weakness, nausea, vomiting, and abdominal pain. Although their bite is painful, fatalities are rare, and an effective antivenom has been available since 1956, with no recorded deaths since its introduction.
Mouse spiders
Mouse spiders (Missulena species) are stout, black or dark blue spiders with a bulbous head and shiny carapace; some males display bright red heads and blue abdomens. They live in burrows across various Australian habitats, particularly in southern and eastern regions. Their venom is considered potentially as toxic as Funnel-web spiders, but severe envenomation is uncommon, and they frequently deliver “dry bites” without injecting venom. Symptoms include pain, swelling, nausea, vomiting, and muscle spasms. No deaths have been recorded, and Funnel-web antivenom is effective in treating their bites.
White-tailed spiders
White-tailed spiders (Lampona species) are common Australian spiders, recognized by their cylindrical, grey-brown bodies and a white spot on their tail end. They are often found indoors in bedding or clothing. Bites typically result in temporary, mild symptoms like localized redness, swelling, pain, itching, or a burning sensation, usually resolving within 24 hours. While anecdotal reports link their bites to necrotic ulcers, scientific studies confirm such severe tissue damage is not a typical outcome. These spiders are not considered medically significant like Funnel-webs or Redbacks, and no fatalities have been recorded from their bites.
First Aid for Spider Bites
Knowing correct first aid for spider bites is important, especially for medically significant species. Always call emergency services (000 in Australia) for any suspected bite from a dangerous spider.
For bites from Funnel-web spiders and Mouse spiders
For Funnel-web and Mouse spider bites, apply the pressure immobilization technique immediately. Wrap an elasticized roller bandage (10-15 cm wide) firmly over the bite site and up the entire limb, as tightly as one would bandage a sprained ankle. Immobilize the bitten limb with a splint to prevent movement, and keep the patient still while awaiting medical assistance. Do not wash the bite area, as venom residue aids identification at the hospital.
For Redback spider bites
First aid for Redback spider bites differs significantly. Wash the bite area with soap and water, and apply a cold pack for 15-minute intervals to alleviate pain and swelling. A pressure bandage should not be used for Redback bites, as their venom spreads slowly, and pressure can intensify pain. Seek medical attention if symptoms are severe or persistent.
For bites from other, less dangerous spiders
For bites from other, less dangerous spiders, wash the area with soap and water and apply a cold pack to reduce discomfort. Over-the-counter pain relief, such as paracetamol or ibuprofen, can be used. Monitor the bite area for worsening symptoms or signs of infection. While rare, some individuals may experience anaphylaxis, requiring immediate emergency medical attention.