number of serious spider bites in Australia. Predominantly neurotoxic to vertebrates, the venom gives rise to the syndrome of latrodectism in humans; this starts with pain around the bite site, which typically becomes severe and progresses up the bitten limb and persists for over 24 hours. Sweating in localised patches of skin occasionally occurs and is highly indicative of latrodectism. Generalised symptoms of nausea, vomiting, headache, and agitation may also occur and indicate severe envenomation. An antivenom has been available since 1956. Taxonomy and naming Common names The common name "redback" is derived from the distinctive red stripe along the dorsal aspect of its abdomen. Other common names include red-striped spider, red-spot spider, jockey spider, Murra-ngura spider, Kapara spider and the Kanna-jeri spider. History Before DNA analysis, the taxonomy of the widow spider genus Latrodectus had been unclear—changes in the number of species reflect the difficulty of using morphology to determine subdivisions within the genus. Substantial interest in their systematics was most likely prompted by the medical importance of these venomous spiders. Swedish arachnologist Tamerlan Thorell described the redback spider in 1870 from specimens collected in Rockhampton and Bowen in central Queensland. He named it Latrodectus hasseltii in honour of colleague A.W.M. van Hasselt. In the same paper, he named a female from Cape York with an all-black abdomen L. scelio, now regarded as the same species. These specimens are in the Naturhistoriska Riksmuseet in Stockholm. German arachnologist Friedrich Dahl revised the genus in 1902 and named L. ancorifer from New Guinea, which was later regarded as a subspecies of the redback. Another subspecies, L. h. aruensis, was described by Norwegian entomologist Embrik Strand in 1911. Subspecies indica (of L. scelio) had been described by Eugène Simon in 1897, but its origin is unclear. Frederick Octavius Pickard-Cambridge questioned Dahl's separating species on what he considered minor anatomical details but Dahl dismissed Pickard-Cambridge as an "ignoramus". Pickard-Cambridge was unsure whether L. hasselti warranted species status, though he confirmed scelio and hasselti as a single species, other researchers such as Ludwig Carl Christian Koch noting the differences to be inconsistent. The redback was also considered by some to be conspecific with the katipō (L. katipo), which is native to New Zealand, though Koch regarded them as distinct. Reviewing the genus Latrodectus in 1959, arachnologist Herbert Walter Levi concluded that the colour variations were largely continuous across the world and were not suitable