Dangerous Australian Spiders

Spiders are among the world's most deadly animals. There are a few venomous Australian spiders, to go with our venomous snakes, but only four species have the potential to give a deadly bite. The four most dangerous are the funnel-web, the redback, the white-tailed and the mouse spiders.

Australian Funnel-Web
The Australian funnel-web spider belongs to the family Hexathelidae. There are about forty species of funnel-web which belong either to the Hadronyche or Atrax genus. The funnel-web is primarily found on the east coast of Australia. It is not found in Western Australia or the Northern Territory.

Only two of the species, the Sydney funnel-web and the northern tree funnel-web, are known to have inflicted fatal bites. The male Sydney funnel-web is regarded as more dangerous than the female which is unusual as it is usually the female that is the most venomous. The funnel-web spider is regarded as one of the three most dangerous spiders in the world.

Funnel-webs burrow under rocks, in rotting logs or rough-barked trees – anywhere that is moist, cool and sheltered. Rockeries and shrubberies are other favoured spots. The burrow is lined with an opaque white silk 'sock' and often has irregular silk trip-lines fanning out from the opening. There is no lid to their burrow.

Sydney funnel-web spiderCredit: Wikimedia

The funnel-web spider is medium to large with body lengths of 1 to 5 cm. They may be black or blue-black, plum-coloured or dark brown. The glossy carapace covers the front part of the body and is devoid of hair. The spinnerets are relatively long. The fangs are large and powerful and can penetrate soft shoe material and even fingernails. The venom glands lie under the chelicerae or mouth parts. The small eyes are closely grouped.

The females are sedentary and spend their lives in their burrow, coming out momentarily to snatch an insect, lizard or frog. Males tend to wander more, looking for mates during warmer weather. They are attracted to water and can survive immersion for several hours should they fall into a swimming pool or paddle pool. They will defend themselves vigorously if they feel threatened. Once they attack, the spider maintains a tight grip and bites repeatedly, thus increasing the risk of imparting large amounts of venom.

Over the last century, there have been 27 deaths recorded from spider bites. Once bitten, there is severe pain. The size of the fangs results in local bleeding. If sufficient venom has been introduced, symptoms occur almost immediately. Symptoms include sweating, twitching, salivation, watery eyes, increased heart rate and rise in blood pressure. These are followed by nausea, vomiting, shortness of breath, confusion, agitation, muscle spasms, pulmonary oedema and extreme hypertension.

Death can occur with 15 minutes (for a small child) to three days. There is antivenom available but speed in getting to medical help is vital if bitten by a funnel-web. The antivenom is fast-acting and effective with no known deaths recorded since its inception.

Redback Spider
The redback spider (Latrodectus hasselti) belongs to the family Theridiidae. It has a fearsome reputation in Australia and is widespread throughout the continent. There have been songs written about the redback and there is even a brand of beer named after the little critter. Only the females are considered dangerous and deaths are not common although a bite will certainly cause illness and uncomfortable symptoms. For children and the elderly, a bite can be potentially fatal.

The females are about a centimetre in diameter. They are jet black with a variable red mark on the abdomen. Immature females are usually brown with whitish markings. Males are small, brown with red and white markings.

RedbackCredit: Vince Evans - Copyright

The web is rough, untidy and very sticky, usually near the ground or tucked in a corner or protective position. The round woolly egg sacs are guarded by the female.

They build large silk webs which are very strong and capable of catching mice or lizards. Drier habitats and built-up areas around buildings, outdoor furniture, machinery, stacked materials, under rims of drums, logs and rocks are all likely to conceal redbacks.

They feed on insects and small vertebrates such as lizards and even mice that may get caught in the strong web. The tiny males are also eaten after mating.

Fertile eggs can be produced by the female up to two years after a single mating. Three to five dirty-white, woolly, spherical sacs are suspended at the back of the web and guarded by the female. After about a fortnight, the little spiders emerge and disperse on the wind. The redback is not aggressive and they rarely leave their webs. Most bites occur by coming into direct contact with the spider or the web.

The bite is very poisonous and causes intense pain. There may be nausea, vomiting, generalised pain, sweating, palpitations, weakness, muscles spasms and fever. Seek medical advice. An antivenom is available commercially and is very effective. Apply iced water and take pain-killers.

White-tailed spider
White-tailed spiders are named for the whitish tips at the end of the abdomen. Common species are Lampona cylindrata and Lampona murina. These two species are difficult to tell apart. Females may reach 18mm in length and males 12mm. The cigar-shaped body is slender and dark-red to grey in colour. The legs have dark orange-brown bands. The abdomen is grey with two pairs of faint white spots and a distinct white spot just above the spinnerets.

Both species are endemic to Australia and have been introduced into New Zealand. They live in gardens beneath bark and rocks and in leaf litter. They also find their way inside and may turn up in folded clothes, towels and shoes. They hunt at night for other spiders and do not build webs.

White-tailed SpiderCredit: Wikimedia - Author TTaylor

White-tails seek out prey and use venom to kill their victims. Symptoms include pain, redness, local swelling and itchiness with occasional nausea, vomiting and headache. The white-tailed was once thought to cause necrosis and ulceration but studies have shown that this cannot be confirmed.

Eggs are laid in a silken brood chamber which is placed in a dark, sheltered place. The eggs are guarded by the female until they hatch.

Mouse Spider
Mouse spiders are a type of trapdoor spider and are sometimes mistaken for the funnel-web. They are found throughout mainland Australia in both coastal and drier habitats from deserts to eucalypt forests. They are not found in tropical rainforest areas or in Tasmania.

They belong to the family Actinopodidae. Of the 11 known species, one is found in Chile and the rest are indigenous to Australia. The evidence suggests that the bite of a mouse spider is potentially as serious as that of the funnel-web. All species have high, bulbous head and jaw regions. The carapace is shiny and smooth. The eyes are spread across the front of the carapace and the spinnerets are short with the last segment domed like a button. The fangs are large and 1 to 2.5 cm in length. The venom is just as dangerous as that of the Sydney funnel-web spider.

Male Mouse SpiderCredit: Wikimedia - Author Bruiser15

The females grow to 3cm long and are black or dark brown. They are very stocky with short, thick legs. Males are smaller with longer legs. Both have huge fangs and fang-bases. There is a very steep slope on the back of the head area.

The large, silk-lined burrows vary between 20 and 55cm deep. The most unusual feature of the main burrow shaft is the two surface hinged-lid trapdoors which are set almost at right angles to each other. The trapdoors merge well into the earth. Having two doors to the burrow increases both prey catching area and efficiency.

A female will spend her entire life in the burrow, only coming out to lunge at passing prey. Males leave their burrows at around 2 to 3 years old to seek a mate. This usually happens after rain. Mating takes place in the burrow of the female and the male then dies.

Spiders usually ambush their prey from the security of the burrows but also forage outside at night. They will tackle ants, beetles, spiders, small lizards and frogs.

Mouse spiders can be aggressive and will bite if provoked. It rears up defensively if disturbed. It is believed the venom of this species is very toxic and they should be treated with caution. Funnel-web antivenom is effective against a mouse spider bite.

Should you be bitten by a spider and think it might be one of these four types, it is best to seek medical help as soon as possible. Take the culprit with you, even if squashed, as this might help determine the best course of action.