Spider Hazards

Spiders recognised as dangerous include true funnel-web spiders, namely the Atrax and Hadronyche species, the redback and brown widow spiders, and the mouse spiders. More information about these Australian spider hazards is also available from the Australian Museum.

What are the presently accepted methods of treating bites by Australian spiders?
At the present time (July 2006) the only antivenoms available for treatment of victims of spider bites are those specific for the redback and funnel-web species, although there is some evidence that the funnel-web antivenom is effective against the venom of the male eastern mouse spider and the redback antivenom also benefits victims of brown widow spider bite. Useful information about treatments for bites by these and other Australian spiders is available online from the Australian Venom Research Unit and the Queensland Museum.

Most dangerous Australian spiders cause their harmful effects on the human body by interfering with the functioning of the nervous system, but the white-tailed spider has long been accused of causing a very different kind of injury. Its venom may be capable of causing necrotising arachnidism, the characteristics of which are an area of inflamed and often ulcerated skin that can continue to enlarge for many weeks and that is generally unresponsive to antibiotics and antiinflammatory agents, although it may sometimes be resolved by hyperbaric oxygen therapy. It should be noted that in 2006 some Australian experts in spider toxinology have expressed strong reservations about the ability of the venom of this spider to produce more than a temporary and localised skin lesion. If more severe and longer lasting damage appears to have been caused, this is suggested to be because of a secondary infection or immunological complication of the biting. More details of the white-tailed spider bite phenomenon and its treatment are available from the Australian Venom Research Unit.

How can dangerous spiders found around the home be eradicated?
It should first be pointed out that most spiders found outside domestic dwellings present an insignificant risk to humans and do not need to be exterminated. Huntsman spiders that have taken up residence on an inside wall or in the mailbox are usually easy to catch in a large glass jar and can then be moved to the nearest tree that has loose bark. Similarly, large orb-weaving spiders that have strung their webs across a walkway can be relocated to any nearby site where their web will not be considered a nuisance. Redback spiders are a significant threat to householders even though they are far more likely to build their webs outside houses and sheds than inside them. It is possible to keep their numbers down by the application of pesticide sprays although this rarely provides a permanent solution to the problem. Some useful information on the habits and control of the redback spider is available from the Queensland Museum.

But what if you live in an area where funnel-webs are known to be present?
There probably isn't any way to ensure your house and garden will be totally free of funnel-webs if you live in a locality where this kind of spider does exist but that doesn't mean you should sell up and move to a safer place. Here are some important facts about South-east Queensland funnel-web species:

1. They do not set up colonies in houses because they can only survive in humid environments and therefore must spend most of their lives in underground burrows. If unable to find their burrows or to quickly build new ones, these spiders will die in a few days, either from dehydration or from attacks by birds, bandicoots or other predators. This would probably happen within the first 24 hours except for the fact that as daylight approaches funnel-webs usually find a dark, damp corner to hide in or build and occupy a retreat under low plants until night falls again. The latter tendency can make funnel-web males a short-term hazard for gardeners who don't take care where they put their hands!

2. Each spider, whether male or female, lives in a separate burrow which is made wider and deeper as the spider grows bigger during the first few years of its life. Funnel-webs rarely leave these burrows during the winter months but may be found waiting for insects at or near the top of the burrow during the evenings at other times of the year.

3. Male funnel-web spiders only develop the anatomical features of males during their breeding season, which on the Darling Downs is November to February. They usually perform their maturation moult only on rainy nights and then wander in search of a burrow that contains a female, never returning to their burrow. Whether they succeed in mating or not they inevitably die within a month or so after maturing.

4. Male funnel-webs cannot jump, though they will rear up impressively when provoked, and they mostly have little tendency to climb and so are unlikely to be found in any room that is accessed only via a flight of steps.

5. Because they must stay in humid conditions, funnel-webs are attracted to ground-level laundries, leaky garden taps, and backyard swimming pools.

6. It is unlikely that funnel-webs will be eradicated by pouring water (even boiling water) down their burrows because these are never vertical and often turn sideways to terminate under a buried stone or tree root. Funnel-webs are also slow to drown and have been known to recover even after 2 days submersion in a swimming pool.

7. Spraying the garden with potent insecticides will not kill funnel-web spiders but will destroy many other harmless small animals. Even spraying directly into each burrow has proven to be an inefficient way to kill these spiders. Somewhat more effective (but still environmentally inappropriate) is the pouring of petrol or diesel fuel down funnel-web burrows.

8. Digging up the spiders one by one will eliminate funnel-webs from a domestic garden and they will take many years to return. Regular cultivation of the soil will also prevent them from establishing burrows. Unfortunately, they can walk several hundred metres in one evening so they could still wander in from a neighbouring property, but of course this will only happen in the few months of their breeding season and even then only after rain.