About the Cover
COVER ILLUSTRATION. The Australian redback spider (Latrodectus hasselti), photographed by Mr Peter Farkas.
Photograph by Mr Peter Farkas, Clinical Photography, Royal Darwin Hospital
The redback spider is a member of the widow spider genus Latrodectus. Widow spiders occur in most parts of the world, and include other important species such as the North American black widow spider (L. mactans), the European widow spider (L. tredecimguttatus) and the widely distributed brown widow spider (L. geometricus). All of the widow spiders are small- to medium-sized, with a globular abdomen, relatively small cephalothorax and long thin legs. The majority have a uniformly black dorsal surface, unlike the redback spider, which has the bright patterning as shown, giving rise to its name. On the ventral surface of the abdomen is an 'hourglass' shaped red area which is characteristic of widow spiders around the world. The male spiders are much smaller than the females and are unlikely to be medically significant, because of the size of their fangs.
The mature female spiders make untidy webs in quiet dark areas: under houses, at the back of garages, under the edges of pot plants, in wood piles, outdoor toilets and under outdoor furniture. The are most commonly found in the warmer months of the year. The widow spiders have unique mating practices where the female eats the male after mating, giving rise to the common name of the genus.
Like other spiders widow spiders produce venom. The venoms of different widow spiders are similar and all contain 
-latrotoxins that appear to be the active toxins in human envenoming. These are large proteins that cause massive release of neurotransmitters, resulting in autonomic and less commonly neuromuscular effects.
Latrodectus species are the most medically significant group of spiders worldwide. Most Latrodectus bites occur when the spider is disturbed in human-made objects, such as shoes, clothes, outdoor furniture, building materials and sheds. The clinical effects of widow spider bite are referred to as latrodectism, and are characterized by severe pain that can occur at the bite site or radiate from the extremities. There may be pain in the abdomen, back and chest. Systemic effects are less common, but include nausea, vomiting, malaise, lethargy, hypertension, local and regional diaphoresis, weakness and muscle cramps. Many other effects have occasionally been reported, such as priapism, patchy paralysis and rhabdomyolysis.
[Table of Contents]
