Spiders are arachnids and not insects. They have eight legs and two body parts. They all spin silk but do not always use it to build webs to catch their prey. Some use traps while others hunt and chase their food.
Spiders are found worldwide, except for Antarctica. There are over 45,000 named species none of which is known to spread disease or parasites. Some have fangs with which they bite, injecting venom, and for this they have gained a fearsome reputation.
Most spiders engage in elaborate courtship rituals. Often this is done so the smaller males are not eaten by the female. In the case of the Redback spider, roughly 60% of males don’t survive the encounter.
Female spiders lay egg sacs that can contain up to 3,000 eggs depending on the species. The females of some species die after laying but others will either hide the egg sac in a nest or drag it around with them to protect it. Inside the egg sac the baby spiders develop until they hatch as spiderlings, miniature versions of the adults, but sexually immature.
With between 2,700 and 3,000 species of spider identified in Australia, and new ones being classified each year, less than a dozen are regarded as harmful. The most likely to be encountered are:
Funnel-web spiders (Atrax species)
There are about 40 species of funnel-web spider in Australia. They are normally black and frequently aggressive. The female Sydney Funnel-web spider (Atrax robustus) can be about 30mm long. The sexes live in separate burrows that are often underneath low-growing plants and located near logs or rocks. There will normally be silk trip lines radiating from the opening of the burrow to alert the spider of prey.
The larger North Coast Funnel-web spider (Atrax formidabilis) is normally found higher up, often in tree holes or crevices in logs. It is 50mm in length.
The male ventures from his burrow in search of a mate in autumn, most often after rain. This is when most people are bitten by this spider. The spiders can live between three and ten years.
Redback spider (Latrodectus hasseltii)
This species is found throughout Australia. Females are around 14mm long, while the male is much smaller at 3mm. The female is black, often with a distinctive red or orange stripe across its abdomen, it is she that bites. They spin their webs in sheltered, dry spots, often in sheds, logs or toilets. These spiders are shy unless provoked and don’t move far from their webs.
White-tailed spider (Lampona cylindrata)
This medium-size species is widespread in the country but found mainly in South East Australia. The female is about 20mm in length, and nearly double the size of the male. The spiders are grey or black in colour with a white spot at the end of their abdomen.
They live mostly on the ground and tend to be found in cupboards, bathrooms, cracks and crevices. Not being web builders, they hunt their prey, which often consists of other spiders.
Mouse spider (Missulena species)
There are eight species of Mouse spider in Australia and they closely resemble funnel-web spiders. They are usually black in colour but may be brown, occasionally with red fangs. The spiders live in burrows with a trapdoor, near bodies of water like rivers and creeks.
Males may wander from the burrows but females and immature spiders remain in them.
Black House spider (Badumna insignis)
This is an unaggressive dark brown or black spider, with females about 18mm long and males half that size. It is the spider most commonly found in buildings in Australia. Webs are spun in undisturbed corners of the home or shed, or around windows, which is why it is also called the Window spider. Outdoors they can be found on tree trunks, fences or logs.
Huntsman spider (family Sparassidae)
In Australia there are at least 94 species of Huntsman spider. Their long, hairy legs and flat bodies give them a frightening appearance, not helped by their size. Females can grow to 45mm across.
Huntsman spiders do not spin webs and tend to live outdoors but may come inside when hunting or when the weather turns colder.
Trapdoor Spiders (Idiopidae species)
Related to Funnel-webs spiders, Trapdoor spiders are brown and live in burrows. Females can be up to 35mm long and may live up to 20 years. Trapdoor spiders can be found throughout Australia but are not as aggressive as Funnel-webs. Not all Trapdoor spiders have a door to their burrows.
Problems caused by spiders
In 2015, residents of Goulburn in New South Wales awoke to find it raining spiders. Literally millions fell from the sky due to an event called ballooning. This is where small spiders throw up a strand of silk to be lifted by the wind so they can travel and extend the range of the species. On rare occasions, these ballooning events can involve huge numbers such as in Goulburn.
Spiders in Australia have a reputation for being among the most deadly in the world. Until recently, there had been no fatal spider bites in Australia since the 1950s due to the introduction of anti-venom. Sadly, in early 2016 a young man walking in the bush in New South Wales was bitten by a Redback spider. Despite treatment, he later died.
Although fatalities are extremely rare, spider bites are not. Roughly 2,000 people a year are reportedly bitten by Redback spiders, with many more suspected but not reported. Anti-venom for Funnel-web spiders has been administered to around 100 people in the past 20 years.
Although none of these have been fatal (except for the one case in 2016), for many the bites were extremely painful. One victim described a Redback bite as feeling as if a nail was being hammered through his hand. He said it was a relief an hour or so later when that pain subsided to an excruciating burning sensation.
The bites of most species cause pain, nausea, sweating, vomiting and headaches. These symptoms will vary depending on the age and general health of the patient. Bites from some species, such as the White-tail spider, House spider, common Black Widow and others, may only be noticed after the event. Blistering and the onset of pain may be the first clues that the person had been bitten
A Funnel-web spider is aggressive and the victim will be aware of the attack due to the immediate pain of the actual bite, or even bites. Any bites from large black spiders (which may be Funnel-webs) should be treated as medical emergencies. If left untreated, some bites can become infected, victims can go into anaphylactic shock or other serious complications can occur.
For Funnel-web spider bites, the pressure-immobilisation first aid technique is recommended. This involves firm pressure being applied over the bitten area while the limb is immobilised. This should be administered by someone familiar with the technique and immediate treatment sought.
The pressure-immobilisation first aid technique should not be used for bites of any spiders other than Funnel-webs. It will increase the pain and can cause complications.
In the majority of cases where a Funnel-web spider is not involved, a cold compress will ease minor pain and swelling. If the pain is bad, then paracetamol can be taken. Anti-histamine tablets may also reduce swelling. The site of the bite should be thoroughly washed and antiseptic applied if available. If the symptoms last more than a few hours or become worse, medical advice should be sought. Although rarely fatal, bites can lead to other problems which will become severe if left untreated.
Victims of spider bites are encouraged to either catch or photograph the spider for identification so that the correct treatment and anti-venom can be administered.
Although spiders are an integral part of Australian life, it is not hard to see why they cause fear and concern. With between 2,700 and 3,000 species of spider identified in Australia, and new ones being classified each year, only a dozen are regarded as harmful.
Spiders have good ecological advantages. They reduce the insect population around our homes. Many people feel that the advantages of having spiders nearby outweigh the disadvantages, but sometimes the numbers get out of hand. This is rarely the case for the dangerous species and is more common with the harmless varieties.
Spiders don’t just live on webs, they can live in burrows or crevices. They will normally be found in the garden but may wander indoors if the weather turns cooler. Attics, cupboards, the kitchen or the bathroom, in fact any room in the house can all support a spider population.
Spider control is an ongoing process. The following simple steps can reduce the number of spiders without involving chemicals:
- Remove all webs
- Spiders eat insects and a home or business that is a good food source will always be attractive. So the first step should be to minimise the food source.
- Turn off outside lights at night, which will attract bugs.
- Physically remove spiders from the house and either kill them or put them back in the garden.
- Make sure all windows and doors are tight-fitting. Seal those that aren’t.
- Tidy the garden or yard.
- Remove all piles of wood, old sheds and other ‘spider homes’.
Chemical treatments can be difficult to use successfully against spiders. Spraying webs can be ineffective as the spiders hang onto it by their claws, so rarely have bodily contact with the poison. Aerosol insect sprays can be used directly on individual spiders or groups when seen. Unfortunately, some are good at keeping out of sight, such as the hunting and crawling spiders, so the opportunity seldom presents itself.
Pyrethrin powder can be effective in attics, basements and infrequently used places. Blanket ground spraying with pesticides can remove crawling spiders but may affect other animals.
The pest controller will need to undertake a thorough visual inspection of all parts of the property to find webs, burrows and potential hiding places, treating each individually as appropriate. As none of the treatments are long lasting, the home or business owner should be warned that the spiders may return.