Spiders in the House and Garden

Almost all spiders possess venom for the purpose of subduing their prey, which are normally insects.

It is sensible to be respectful of spiders, rather than frightened of them.

Almost all spiders possess venom for the purpose of subduing their prey - normally insects. This makes spiders one of the most beneficial of invertebrate groups. Spider venom is occasionally used against humans. This usually happens when the spider is trying to defend itself. While many spiders are not able to penetrate human skin with their fangs, those that can occasionally inflict painful and, in rare cases, dangerous bites.

Eliminating spiders from an area for a long period of time is almost impossible. Spiders do not congregate in a single large nest, so the population cannot be destroyed by targeting one site. New spiders will quickly recolonise an area if the inhabitants are killed off. In many species, young spiders (or 'spiderlings') disperse by 'ballooning'. They spin silk strands that are taken by the wind, carrying the spiders over potentially long distances.

Although keeping an area free of spiders is difficult, there are many precautions that can be taken to avoid bites. Avoid walking outside with bare feet, especially at night. When gardening, wear shoes, long trousers and thick gloves to guard against any spiders, scorpions, centipedes or stinging insects.

Wandering spiders can enter houses at ground level, often under a door. Fitting weather strips or using draft excluders can block this entry route. Fitting fly-screens to windows and wall ventilators will prevent any climbing spiders from obtaining access. A cleared area around the house will discourage burrowing spiders from making burrows there.

It is a good idea to educate children to 'look but don't touch' when they find any spiders, and for adults to obey the same rule. It is sensible to be respectful of spiders, rather than frightened of them.

Signs

Funnel-web burrows are distinguished from other holes in the ground by the presence of a series of irregular silk 'trip-lines' radiating out from the entrance. Holes are normally found in moist, shaded areas like rockeries, dense shrubs, logs and leaf litter. A small, neat hole lined with a collar of silk which does not extend more than a centimetre from the rim could belong to a trapdoor spider (the common Brown Trapdoor Spider does not build a 'door' for its burrow). Other possible hole owners include mouse spiders, wolf spiders or insects (most commonly cicadas or ants).

The female Funnel-web does not normally leave her burrow, but may be unearthed by excavations, rubbish removal or gardening, or be driven out by heavy rain. Male Funnel-webs leave their burrows to search for females in summer and autumn, and are normally active at night. Wandering spiders are frequently encountered after a period of wet weather.

Treatment

Insecticide spraying is not recommended for ground-dwelling spiders. Such sprays may affect other animals. The target spiders often are not killed by the spray. Instead, the chemical may actually make them more active (and therefore more likely to enter homes). Sprays are also unlikely to give any lasting protection against Funnel-web Spiders. Funnel-webs in burrows close to houses can be attacked individually, by pouring boiling water down the burrows. It is sensible to wear gloves and shoes while doing this, as spiders not killed may quickly run out of the burrow.

Precautions

In areas known to have Funnel-web populations, there are a number of precautions that can be taken to reduce the risk of bites. Wandering spiders can enter houses at ground level, often under a door. Fitting weather strips or using draft excluders can block this entry route. A cleared area around the house will discourage Funnel-webs from making burrows there.

Inside a house, Funnel-web spiders will seek shelter to avoid drying out. Consequently it's important to check clothing, shoes or bedding close to, or on the floor, for spiders. The same goes for any shoes or clothing left outdoors or around camp-sites in Funnel-web areas.

Funnel-web Spiders often fall into swimming pools. Spiders can trap a small bubble of air in hairs around the abdomen which aids both breathing and floating, so it should not be assumed that a spider on a pool bottom has drowned. Funnel-webs have been known to survive 24-30 hours under water.

Signs

Redbacks are common in urban habitats such as garden sheds, under steps or logs and around swimming pools or piles of rubbish. They build webs in dry, sheltered sites, often with the upper part of the web hidden from sunlight. The spider hides in a funnel-shaped retreat at the top of the web. The lower part of the web consists of a forest of mostly vertical, sticky catching threads.

Treatment

Surface sprays applied directly will kill Redback Spiders. However treatment must be repeated often to deal with spiders which are carried in on the wind. Such insecticides will also affect many non-target species.

An effective way of controlling Redbacks is to carry out regular inspections of suitable Redback habitats, searching for spiders and their webs. The spiders may be removed by pushing a stick into the back of the web and twisting the web, spider and any egg sacs around it. If all the webs on a property are removed, new arrivals will quickly become apparent by the presence of new webs.

Precautions

As Redbacks generally make their webs under some form of shelter, they are often not seen. Check any potential web sites before putting your hands there. Wear gloves when gardening.

Signs

As White-tailed Spiders do not make webs, there are no signs to look for, other than the presence of the spiders themselves. They are often found in bathrooms and laundries.

Treatment

These spiders are both nomadic and common, so any control measure will be only a short term solution. If there is a population of these spiders in your area, then they are likely to re-enter houses after the effects of insecticides have worn off.

Precautions

If you know that White-tailed Spiders are present in your area, check your shoes and clothing before wearing them. It is also sensible to check for them in bedding and laundry. White-tails are normally active at night. Any wandering spiders seen indoors should be removed from the house.

There is usually no need to control other species of spider. If an orb-weaving spider consistently builds a web across a frequently-used path, the spider may be moved to a safer site.

Black House or Window Spiders are shy, and are quick to hide in the retreat at the back of their webs if disturbed. Webs are often made in the corners of windows, and may have a funnel-shaped retreat in which the spider shelters. The web may be removed using a broom, or a stick (the same method as for Redbacks), and the spider deposited outside.

It should be noted that Black House Spiders are known to kill and eat Redback Spiders, and that their presence may reduce the chances of large Redback populations becoming established in your area. On the other hand, they are a favoured food of the White-tailed Spider.

Wandering spiders such as wolf spiders and huntsman spiders are best dealt with on an individual basis when encountered. They should be left alone if in the garden, or removed from a house using a broom. They are fast moving, but not normally aggressive.

Huntsman spiders can be disconcerting when they jump off walls to make their escape, or appear unexpectedly in your car. Make sure car windows and doors are closed when the car is parked - particularly at night. If a spider is found in a car but evades capture, it can be encouraged to leave by parking the car in a warm place.

Like Funnel-webs, Brown Trapdoor Spiders and mouse spiders are often found in swimming pools, or unearthed during gardening or construction work. Male trapdoor spiders wander during summer and autumn. They make a burrow with a neat silk collar around the inside, and no trip-lines radiating outwards.

Male mouse spiders are more common later in the year - wandering from April to June - and tend to be active by day. Males of the two species common in New South Wales are easily recognisable by having either a red head and jaw area (Red-headed Mouse Spider), or a pale blue-white patch in front of the abdomen (Eastern Mouse Spider). All female mouse spiders are dark brown to black. The female Red-headed Mouse Spider makes a deep burrow closed above by two trapdoors set a right angles to each other.

Precautions for both trapdoor and mouse spiders are the same as for Funnel-webs. As they are often confused with the Funnel-web, it is wise to treat any bite with caution, especially if the bite is on a child. Trapdoor spider venom is not considered to be dangerous to humans. The venom of mouse spiders, on the other hand, may be highly toxic, and bites should be taken seriously. If possible, capture the spider and have it positively identified.

First Aid

For all spiders, except Funnel-web spiders and mouse spiders, the only first aid necessary is the application of an ice-pack to relieve pain, if needed. If symptoms are serious or persist, seek medical attention, and always do so in the case of a Redback Spider bite. For suspected Funnel-web or mouse spider bites, a pressure bandage should be applied to the bitten area as soon as possible, and the victim kept quiet and medical attention sought.