The Australian Redback Spider

The Australian Redback, Latrodectus hasselti, belongs to a group of spiders known throughout the world as Black Widows (genus Latrodectus). It is currently believed to be a species distinct to Australia, and presumably has been exported to Dubai from there. It has also been reported in New Zealand, Japan and Tristan de Cunha. In all cases, exported goods from Australia were responsible for its translocation.

Its importance to us lies in the ability of the female spider to deliver a bite dangerous or even fatal to humans. Prior to the introduction of a specific antivenom in 1956, thirteen deaths in Australia were known to have been caused by Redback spider bite. It is one of Australia's best known spiders, earning it's reputation through "a large proportion of the recorded bites having been sustained in outdoor privies" (Taylor and Murray 1946). That activity, wrongly attributed to the male, was immortalised in Australian singer Slim Newton's 1972 hit song, "The Redback on the toilet seat":

'There was a Redback on the toilet seat when I was there last night.
I didn't see him in the dark but, boy, I felt his bite'.

But enough of Australian culture.

Habitat

Redbacks like warm, dry and sunny areas and tend to avoid damp and shade. They prefer to build their webs in locations where the outer part of the web has some exposure to sunlight, and the inner part is tucked away in a cool, dark recess. Under window-sills and garden chairs, and among garden tools and unused flower-pots are common sites. I found one in the dog-kennel and another in the bark of an old tree stump, but even behind car bumpers and in the handles of motor bikes has been reported. They will enter houses and build their webs inside if the right conditions are present (e.g. at the sides of patio doors).

Recognition

The adult female usually has a satin-black body ands thin, black legs. Overall length is ordinarily about 15 to 30 cm. The distinctive markings are on the abdomen: on the back is a red area in the shape of an hourglass or two triangles while the underside (ventral aspect) has a distinct red stripe beginning just in front of the middle. Variations upon this pattern are common - in Australia, at least - but the hourglass mark is always evident to some extent. The photo above has a flash reflection on the "hourglass", but it can still be easily be made out.

The Bite, its Symptoms, and Treatment

Only the female is large enough to bite people effectively. The initial bite is often felt but is usually painless, although burning sensations have been reported by some. Puncture marks are not always evident. In the majority of cases, intense local pain is felt about 5 minutes after the bite, and the diagnostic indication of Redback bite is localised sweating at the site of the bite. In almost 40 percent of cases, symptoms include weakness, numbness, paralysis and loss of coordination. In about 10 percent, more severe symptoms such as spasms, shock and convulsions can occur. It is recommended that NO special first aid be applied because, as the venom is slow acting, localising it may intensify pain at the site of the bite. The best course of action is to transport the person immediately and without panic to medical aid. Serious illness apparently does not develop for at least three hours.

Control

Redbacks are tough creatures that are difficult to eradicate. The warm, dry climate of the Emirates is ideal for them and they can breed prolifically. The female is capable of storing the sperm of a male and using it over a period of up to two years to lay several batches of eggs. The eradication or absence of males, therefore, is no guarantee that the female cannot produce more young.

The Queensland Museum of Arachnology advises 'informed vigilance' as the best method of Redback control. Look in sites in a sunny location that have shade nearby. The web is fine, but strong enough to hold dead leaves blown into it. Roll web, eggs and spider (if possible) onto a stick and then destroy them. Check around that area for other webs. Keep checking weekly, and remember that Redbacks dislike shady, damp conditions so are often absent in gardens that are well kept and watered, with plenty of shade.

Australian Redback spiders are probably present in our gardens and barbecue areas, among our garden tools, under our sun-loungers, and possibly even in our homes. Any creature as small as this capable of causing severe illness or possibly even death should command our attention and respect. I have not yet been able to find out if local hospitals carry the antivenom; frankly, I doubt it. But care, and awareness of the problem, goes a long way to preventing an unnecessary accident, especially in homes with small children.

To quote the Queensland Museum of Arachnology once again, "GOOD LUCK!"