<P> The redback spider has been historically responsible for more envenomations requiring antivenom than any other creature in Australia, however by 2017 the spider was blamed for only 250 envenomations requiring antivenom annually . Estimates of the number of people thought to be bitten by redback spiders each year across Australia range from 2,000 to 10,000 . The larger female spider is responsible for almost all cases of redback spider bites . The smaller male was thought to be unable to envenomate a human, although some cases have been reported; their rarity is probably due to the male's smaller size and proportionally smaller fangs, rather than the male being incapable of biting or lacking potent venom . The bite from both juvenile and mature females appears to have similar potency . The male bite usually only produces short - lived, mild pain . Most bites occur in the warmer months between December and April, in the afternoon or evening . As the female redback is slow - moving and rarely leaves her web, bites generally occur as a result of placing a hand or other body part too close to the spider, such as when reaching into dark holes or wall cavities . Bites often also occur when a hidden spider is disturbed in items such as clothes, shoes, gloves, building materials, garden tools or children's outdoor toys . </P> <P> A 2004 review reported 46% of bites occurring on distal extremities of the limbs, 25% on proximal areas of limbs (upper arms and thighs), 21% on the trunk, and 7% on the head or neck . In some cases the same spider bites a victim multiple times . Historically, victims were often bitten on the genitalia, though this phenomenon disappeared as outhouses were superseded by plumbed indoor toilets . Conversely, bites on the head and neck have increased with use of safety helmets and ear muffs . Precautions to avoid being bitten include wearing gloves and shoes while gardening, not leaving clothes on the floor, and shaking out gloves or shoes before putting them on . Also, children can be educated not to touch spiders . </P> <P> The redback and its relatives in the genus Latrodectus are considered dangerous, alongside funnel - web spiders (Atrax and Hadronyche), mouse spiders (Missulena), banana spiders (Phoneutria) and recluse spiders (Loxosceles). Venom is produced by holocrine glands in the spider's chelicerae (mouth parts). Venom accumulates in the lumen of the glands and passes through paired ducts into the spider's two hollow fangs . The venom of the redback spider is thought to be similar to that of the other Latrodectus spiders . It contains a complex mixture of cellular constituents, enzymes and a number of high - molecular - weight toxins, including insect toxins and a vertebrate neurotoxin called alpha - latrotoxin, which causes intense pain in humans . </P> <P> In vertebrates, alpha - latrotoxin produces its effect through destabilisation of cell membranes and degranulation of nerve terminals, resulting in excessive release of neurotransmitters, namely acetylcholine, norepinephrine and GABA . Excess neurotransmitter activity leads to clinical manifestations of envenomation, although the precise mechanisms are not well understood . Acetylcholine release accounts for neuromuscular manifestations, and norepinephrine release accounts for the cardiovascular manifestations . Female redbacks have an average of around 0.08--0.10 mg of venom, and experiments indicate that the median lethal dose (LD) for mice at room temperature is 10--20% of this quantity (0.27--0.91 mg / kg based on the mass of the mice used), but that it is considerably deadlier for mice kept at lower or higher temperatures . Pure alpha - latrotoxin has an LD in mice of 20--40 μg / kg . </P>

Big black spider with red stripe on back