Editing Redback spider

{{Short description|Species of spider}}
{{Featured article}}
{{Use dmy dates|date=December 2020}}
{{Use Australian English|date=August 2011}}
{{Speciesbox
 | name                = Redback spider
 | taxon               = Latrodectus hasselti
 | image               = Latrodectus hasselti close.jpg
 | image_caption       = Adult female red back spider
 | image2              = Latrodectus hasselti male.png
 | image2_caption      = Adult male (considerably smaller than female)
 | authority           = [[Tord Tamerlan Teodor Thorell|Thorell]], 1870<ref name=WSC_s39048/>
 | synonyms            = {{plainlist}}
* ''Latrodectus hasseltii'' {{small|[[Tamerlan Thorell|Thorell]], 1870}}
* ''Latrodectus scelio'' {{small|[[Tamerlan Thorell|Thorell]], 1870}}
* ''Latrodectus scelio indicus'' {{small|[[Eugène Simon|Simon]], 1897}}
* ''Latrodectus indicus''  {{small|[[Reginald Innes Pocock|Pocock]], 1900}}
* ''Latrodectus hasselti indicus'' {{small|[[Frederick Octavius Pickard-Cambridge|Pickard-Cambridge]], 1902}}
* ''Latrodectus ancorifer'' {{small|[[Friedrich Dahl|Dahl]], 1902}}
* ''Latrodectus hasselti aruensis'' {{small|[[Embrik Strand|Strand]], 1911}}
* ''Latrodectus hasselti ancorifer'' {{small|[[Władysław Kulczyński|Kulczyński]], 1911}}
* ''Latrodectus cinctus'' {{small|[rejected] [[Berta S. Gerschman de Pikelin|Gerschman]] & [[Rita D. Schiapelli|Schiapelli]], 1942}}
* ''Latrodectus mactans hasselti'' {{small|[[Pater Chrysanthus|Chrysanthus]], 1975}}
{{endplainlist}}
 | synonyms_ref        = <ref name=WSC_s39048>{{cite web |title=Taxon details ''Latrodectus hasselti'' Thorell, 1870 |work=World Spider Catalog |publisher=Natural History Museum Bern |url=https://wsc.nmbe.ch/species/39048 |access-date=12 May 2025|url-status=live }}</ref>
}}

The '''redback spider''' ('''''Latrodectus hasselti'''''), also known as the '''Australian black widow''',<ref name=":2">{{Cite journal|title=The multiple actions of black widow spider toxins and their selective use in neurosecretion studies|last=Ushkaryov|first=Y. A.|volume=213|issue=5|pages=527–42|journal=Toxicon|year=2004|doi=10.1016/j.toxicon.2004.02.008|pmid=15066411|bibcode=2004Txcn...43..527U }}</ref><ref>{{Cite book|title=Recent Insights in Latrodectus ("Black Widow" Spider) Envenomation: Toxins and Their Mechanisms of Action|last=Rodrigues Peres|first=O.|publisher=Springer|pages=333–44|year=2016|doi=10.1007/978-94-007-6389-0_23|isbn=978-94-007-6388-3}}</ref><ref name=":4">{{Cite book|chapter=Impact of Non-native Animals and Plants on Human Health|last=Nentwig|first=N.|title=Impact of Biological Invasions on Ecosystem Services|publisher=Springer|year=2017|pages=277–93| doi=10.1007/978-3-319-45121-3_18|isbn=978-3-319-45119-0}}</ref>  is a [[species]] of highly venomous [[spider]] believed to originate in Australia, but which is now found in [[Southeast Asia]]  and [[New Zealand]]. It has also been found in packing crates in the United States with colonies elsewhere outside Australia.<ref name=":5">{{Cite book|title=A field guide to spiders of Australia.|last=Whyte|first=Robert|date=2017|publisher=CSIRO Publishing|isbn=9780643107076|location=Clayton, VIC Australia|pages=321, 339|oclc=971943480}}</ref> It is a member of the [[Cosmopolitan distribution|cosmopolitan]] genus ''[[Latrodectus]]'', the widow spiders. The adult female is easily recognised by her spherical black body with a prominent red stripe on the upper side of her abdomen and an hourglass-shaped red/orange streak on the underside. Females usually have a body length of about {{convert|10|mm|sigfig=1}}, while the male is much smaller, being only {{convert|3|–|4|mm|in|abbr=on}} long.

Mainly nocturnal, the female redback lives in an untidy web in a warm sheltered location, commonly near or inside human residences. It preys on insects, spiders and small vertebrates that become ensnared in its web. It kills its prey by injecting a complex [[venom]] through its two fangs when it bites, before wrapping them in silk and sucking out the liquefied insides. Often, it first squirts its victim with what resembles 'superglue' from its spinnerets, immobilising the prey by sticking the victim's limbs and appendages to its own body. The redback spider then trusses the victim with silk. Once its prey is restrained, it is bitten repeatedly on the head, body and leg segments and is then hauled back to the redback spider's retreat. Sometimes a potentially dangerous victim can be left to struggle for hours until it is exhausted enough to approach safely.<ref name=":5" /> Male spiders and spiderlings often live on the periphery of the female spiders' web and steal leftovers. Other species of spider and [[parasitoid]] wasps prey on this species. The redback is one of a number of [[arachnid]]s that usually display [[sexual cannibalism]] while mating.

After mating, sperm is [[Female sperm storage|stored]] in the [[spermathecae]], organs of the female reproductive tract, and can be used up to two years later to fertilise several clutches of eggs. Each clutch averages 250 eggs and is housed in a round white silken egg sac. The redback spider has a widespread distribution in Australia, and inadvertent introductions have led to established colonies in New Zealand, the United Arab Emirates, Japan<ref>{{Cite news|url=https://theconversation.com/hidden-housemates-the-australian-redback-spider-55570|title=Hidden housemates: the Australian redback spider|last=Saez|first=Natalie J.|work=The Conversation|access-date=1 October 2017|language=en|archive-date=1 October 2017|archive-url=https://web.archive.org/web/20171001212848/https://theconversation.com/hidden-housemates-the-australian-redback-spider-55570|url-status=live}}</ref> and greenhouses in Belgium{{cn|date=March 2025}}.

The redback is one of the few spider species that can be seriously harmful to humans, and its liking for habitats in built structures has led it to being responsible for a large number of serious [[Spider bite#Spider venom|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,<ref name=SMH1907/> red-spot spider, jockey spider,<ref>{{cite news |url=http://nla.gov.au/nla.news-article41605415 |title=Poisonous Spiders |newspaper=[[The West Australian]] |location=Perth |date=8 January 1938 |page=19 |publisher=National Library of Australia |access-date=13 September 2013 |archive-date=19 October 2021 |archive-url=https://web.archive.org/web/20211019062746/https://trove.nla.gov.au/newspaper/article/41605415 |url-status=live }}</ref> Murra-ngura spider, Kapara spider and the Kanna-jeri spider.<ref>{{cite book|editor1=Platnick, N. |editor2=Merrett, P. |editor3=Brignoli, P. M. | year=1990| title=Advances in Spider Taxonomy, 1981–1987. A Supplement to Brignoli's "a Catalogue of the Araneae Described Between 1940–1981" | publisher=Manchester University Press | location=Manchester, United Kingdom| isbn=0-7190-2782-9 }}</ref>

===History===
Before [[DNA]] analysis, the [[Taxonomy (biology)|taxonomy]] of the widow spider genus ''[[Latrodectus]]'' had been unclear—changes in the number of species reflect the difficulty of using [[Morphology (biology)|morphology]] to determine subdivisions within the genus.<ref name="garb 2004"/> Substantial interest in their systematics was most likely prompted by the medical importance of these venomous spiders.<!--garb ref for previous two sentences--><ref name="garb 2004"/> Swedish arachnologist [[Tamerlan Thorell]] described the redback spider in 1870<ref name=thorell>{{cite journal | author= Thorell, Tamerlan |year=1870|title= Araneae Nonnullae Novae Hollandiae, Descriptae |language=la |journal= Öfversigt Af Kongelige Vetenskaps-Akademiens Förhandlingar, Stockholm |volume= 27 |pages= 367–89 [369–71] |url=https://archive.org/stream/fversigtafkongl21vetegoog}}</ref> from specimens collected in [[Rockhampton]] and [[Bowen, Queensland|Bowen]] in central Queensland.<ref name="FOPC">{{cite journal|last=Pickard-Cambridge|first=Frederick Octavius |year=1902|title=On the Spiders of the Genus ''Latrodectus'' Walckenaer|journal=Proceedings of the Zoological Society of London|volume=1|pages=247–61 [255, 258–59] |url=https://archive.org/stream/cbarchive_101275_onthespidersofthegenuslatrodec1833/onthespidersofthegenuslatrodec1833#page/n17/mode/2up}}</ref> He named it ''Latrodectus hasseltii'' in honour of colleague A.W.M. van Hasselt.<ref name="Species bank">{{cite web|url=http://www.environment.gov.au/cgi-bin/species-bank/sbank-treatment.pl?id=69198|title=''Latrodectus hasseltii'' (Family Theridiidae)|last=Gray|first=M. R.|date=7 February 2007|work=Department of Sustainability, Environment, Water, Population and Communities: Species Bank|publisher=Australian Government|access-date=8 September 2013|location=Canberra, Australian Capital Territory|archive-date=10 September 2014|archive-url=https://web.archive.org/web/20140910150536/http://www.environment.gov.au/cgi-bin/species-bank/sbank-treatment.pl?id=69198|url-status=live}}</ref> In the same paper, he named a female from [[Cape York Peninsula|Cape York]] with an all-black abdomen ''L. scelio'',<ref name=thorell/><ref name="FOPC"/> now regarded as the same species. These specimens are in the [[Swedish Museum of Natural History|Naturhistoriska Riksmuseet]] in Stockholm.<ref name="levi 1959"/><!-- cites previous 1.5 sentences --> Between 1872 and 1972, all subsequent authors spelled the species name as ''hasselti'', and that altered spelling is maintained today.<ref name=WSC_s39048 />

German arachnologist [[Friedrich Dahl]] revised the genus in 1902 and named ''L. ancorifer'' from New Guinea,<ref name=dahl>{{cite journal |author=Dahl, Friedrich |year=1902 |language=de |title=Über algebrochene Copulationsorgane männlicher Spinnen im Körper der Weibchen |journal=Sitzungsberichte der Gesellschaft Naturforschender Freunde zu Berlin |volume=1902 |pages=36–45 [43] |url=https://www.biodiversitylibrary.org/page/7931174 |access-date=20 February 2018 |archive-date=6 March 2016 |archive-url=https://web.archive.org/web/20160306094755/http://biodiversitylibrary.org/page/7931174 |url-status=live }}</ref> 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.<ref name="levi 1959"/> [[Frederick Octavius Pickard-Cambridge]] questioned Dahl's separating [[species]] on what he considered minor anatomical details but Dahl dismissed Pickard-Cambridge as an "ignoramus".<ref name="levi 1959"/> Pickard-Cambridge was unsure whether ''L. hasselti'' warranted species status, though he confirmed ''scelio'' and ''hasselti'' as a single species,<ref name="FOPC"/> other researchers such as [[Ludwig Carl Christian Koch]] noting the differences to be inconsistent.<ref name=SMH1907>{{cite news |url=http://nla.gov.au/nla.news-article14853380 |title=The Red-striped Spider |newspaper=[[The Sydney Morning Herald]] |date=23 March 1907 |page=6 |publisher=National Library of Australia |author=Rainbow, William Joseph |access-date=1 September 2013 |archive-date=19 October 2021 |archive-url=https://web.archive.org/web/20211019062746/https://trove.nla.gov.au/newspaper/article/14853380 |url-status=live }}</ref> The redback was also considered by some to be conspecific with the [[katipō]] (''L. katipo''), which is native to New Zealand,<ref name=Camperdown1893>{{cite news |url=http://nla.gov.au/nla.news-article19363887 |title=The Deadly Red-Backed Spider. |newspaper=[[The Camperdown Chronicle]] |location=Camperdown, Victoria |date=1 June 1893 |page=3 |publisher=National Library of Australia |access-date=31 August 2013 |archive-date=19 October 2021 |archive-url=https://web.archive.org/web/20211019062746/https://trove.nla.gov.au/newspaper/article/19363887 |url-status=live }}</ref> though Koch regarded them as distinct.<ref name=SMH1907/>

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 for distinguishing the individual species. Instead, he focused on differences in the morphology of the female sexual organs, and revised the number of recognised species from 22 to 6. This included reclassifying the redback and several other species as subspecies of the best-known member of the group, the black widow spider (''[[Latrodectus mactans]]''), found in North America and other regions.<ref name="garb 2004"/> He did not consider the subspecies ''L. h. ancorifer'', ''L. h. aruensis'' and ''L. h. indicus'' distinct enough to warrant recognition.<ref name="levi 1959">{{cite journal|last=Levi |first= Herbert Walter |year=1959|title=The Spider Genus ''Latrodectus'' (Araneae, Theridiidae)|journal=Transactions of the American Microscopical Society|volume=78|issue=1|pages=7–43|jstor=3223799|doi=10.2307/3223799}}</ref> Subsequently, more reliable genetic studies have split the genus into about 30 species, and the redback has no recognised subspecies in modern classifications.<ref name="garb 2004"/><ref name="AFD">{{cite web|url=http://www.environment.gov.au/biodiversity/abrs/online-resources/fauna/afd/taxa/Latrodectus_hasseltii |title=Species ''Latrodectus hasseltii'' Thorell, 1870|author=Department of Sustainability, Environment, Water, Population and Communities |date=25 October 2012|work=Australian Faunal Directory |publisher=Australian Government|access-date=8 September 2013|location=Canberra|archive-url=https://web.archive.org/web/20130921061610/http://www.environment.gov.au/biodiversity/abrs/online-resources/fauna/afd/taxa/Latrodectus_hasseltii|archive-date=21 September 2013|url-status=dead}}</ref>

===Placement===
A member of the genus ''Latrodectus'' in the family [[Theridiidae]], the redback belongs in a [[clade]] with the black widow spider,<ref name="garb 2004"/> with the [[katipō]] as its closest relative.<ref name="vink"/> A 2004 molecular study supports the redback's status as a distinct species, as does the unique abdomen-presenting behaviour of the male during mating.<ref name="garb 2004"/> The close relationship between the two species is shown when mating: the male redback is able to successfully mate with a female katipō producing [[Hybrid (biology)|hybrid]] offspring. However, the male katipō is too heavy to mate with the female redback, as it triggers a predatory response in the female when it approaches the web, causing the female to eat it.<ref name="Riordan">{{cite web | title =Species Profile: Katipo Spider | first =Hilary Ann | last =Riordan | publisher =CanterburyNature | date =July 2005 | url =http://www.canterburynature.org/species/lincoln_essays/katipo.php | access-date =27 May 2008 | url-status =dead | archive-url =https://web.archive.org/web/20090328215538/http://www.canterburynature.org/species/lincoln_essays/katipo.php | archive-date =28 March 2009 | df =dmy-all }}</ref> There is evidence of interbreeding between female katipō and male redbacks in the wild.<ref name="vink">{{cite journal |last1=Vink|first1=Cor J.|last2=Sirvid|first2=Phil J.|last3=Malumbres-Olarte|first3=Jagoba|last4=Griffiths|first4=James W.|last5=Paquin|first5=Pierre|last6=Paterson|first6=Adrian M. |title=Species Status and Conservation Issues of New Zealand's Endemic ''Latrodectus'' Spider Species (Araneae: Theridiidae) |journal=Invertebrate Systematics |volume=22 |issue=6 |pages=589–604 |year=2008 |doi=10.1071/IS08027 |issn=1445-5226 |oclc=50150601 |publisher=[[CSIRO]] Publishing |location=Collingwood, Victoria, Australia}}</ref><ref>{{cite web|url=http://www.stuff.co.nz/science/85767262/Katipo-faces-challenges-from-Australian-and-South-African-spider-relatives|title=Katipo faces challenges from Australian and South African spider relatives|date=31 October 2016|access-date=31 October 2016|first=Mick|last=Whittle|publisher=Stuff|archive-date=10 July 2018|archive-url=https://web.archive.org/web/20180710080657/https://www.stuff.co.nz/science/85767262/Katipo-faces-challenges-from-Australian-and-South-African-spider-relatives|url-status=live}}</ref>

==Description==
{{Further|Spider anatomy}}
[[File:RedbackPottingMix.JPG|thumb|right|A juvenile female, showing typical white banding]]
The adult female redback has a body around {{convert|1|cm|sigfig=1}} long, with slender legs, the first pair of which are longer than the rest.{{sfn|Sutherland|Tibballs|2001|p=385}} The round [[abdomen]] is a deep black (occasionally brownish), with a red (sometimes orange) longitudinal stripe on the upper surface and an hourglass-shaped [[Scarlet (color)|scarlet]] streak on the underside.<ref name="Amo-Redback"/> Females with incomplete markings or all-black abdomens occasionally occur.{{sfn|Brunet|1997|p=148}} The [[cephalothorax]] is much smaller than the abdomen, and is black.{{sfn|Sutherland|Tibballs|2001|p=385}} Redback spiderlings are grey with dark spots,<ref name=SMH1907/> and become darker with each [[Moulting|moult]].<ref name="rauber83">{{cite journal|last=Rauber|first=Albert|year=1983|title=Black Widow Spider Bites|journal=Clinical Toxicology|type=Review|volume=21|issue=4–5|pages=473–85|doi=10.3109/15563658308990435|pmid=6381753}}</ref> Juvenile females have additional white markings on the abdomen.<ref name="Amo-Redback"/> The bright [[Scarlet (color)|scarlet]] red colours may serve as a warning to potential predators.<ref name=Forster1989/> Each spider has a pair of venom glands, one attached to each of its [[chelicerae]]<ref>{{cite journal|last=Wiener|first=Saul|title=The Australian Red Back Spider (Latrodectus Hasseltii): I. Preparation of Antiserum by the Use of Venom Adsorbed on Aluminium Phosphate|journal=The Medical Journal of Australia|date=5 May 1956|volume=43|pages=739–42|pmid=13321231|issue=15|doi=10.5694/j.1326-5377.1956.tb35749.x}}</ref> with very small fangs.<ref>{{cite web|last=Delaney|first=Anne|title=Redback Spiders – on Toilet Seats and Water Troughs|url=http://www.abc.net.au/local/stories/2008/01/10/2135593.htm|publisher=Australian Broadcasting Corporation|access-date=18 October 2013|date=10 January 2008|archive-date=28 October 2013|archive-url=https://web.archive.org/web/20131028235529/http://www.abc.net.au/local/stories/2008/01/10/2135593.htm|url-status=live}}</ref> Small compared to the female,<ref>{{cite web|url=http://museumvictoria.com.au/discoverycentre/infosheets/spiders-found-in-victoria/red-back-spider/|title=Red-back Spider ''Latrodectus hasseltii''|author=Discovery Centre|work=Spider of Victoria series|publisher=Museum Victoria|access-date=18 October 2013|url-status=dead|archive-url=https://web.archive.org/web/20131019044548/http://museumvictoria.com.au/discoverycentre/infosheets/spiders-found-in-victoria/red-back-spider/|archive-date=19 October 2013}}</ref> the male redback is {{convert|3|–|4|mm|in|abbr=on}} long and is light brown, with white markings on the upper side of the abdomen and a pale hourglass marking on the underside.<ref name="Amo-Redback">{{cite web | author=Australian Museum | title=Animal Species: Redback Spider, ''Latrodectus hasselti'' | url=https://australian.museum/learn/animals/spiders/redback-spider/ | access-date=5 September 2013 | archive-date=6 July 2020 | archive-url=https://web.archive.org/web/20200706143955/https://australian.museum/learn/animals/spiders/redback-spider/ | url-status=live }}</ref>

Another species in Australia with a similar physique, ''[[Steatoda capensis]]'', has been termed the "false redback spider", but it is uniformly black (or plum), and does not display the red stripe.<ref name=Warden1989>{{cite news |first=Ian |last=Warden |url=http://nla.gov.au/nla.news-article118118613 |title=Red-back Spider that is Not. |newspaper=[[The Canberra Times]] |date=12 February 1987 |page=1 |publisher=National Library of Australia |access-date=4 September 2013 |archive-date=19 October 2021 |archive-url=https://web.archive.org/web/20211019062747/https://trove.nla.gov.au/newspaper/article/118118613 |url-status=live }}</ref>

==Behaviour==
{{Further|Spider behaviour}}
[[File:Redback spider in its web.jpg|thumb|right|Female in its web]]

===Web===
The redback is mainly nocturnal;<ref name="andrade1998"/> the female remains concealed during the day, and spins her web during the night,<ref name=SMH1907/> usually remaining in the same location for most of her adult life.<ref name=Andrade2002/> Classified as a gum-footed tangle web, the web is an irregular-looking tangle of fine but strong silk. Although the threads seem random, they are strategically placed for support and entrapment of prey.{{sfn|Brunet|1997|p=141}} The rear portion of the web forms a funnel-like retreat area where the spider and egg sacs are found. This area has vertical, sticky catching threads that run to ground attachments.<ref name="Amo-Redback"/> The vertical strands act as trip wires to initially alert the spider to the presence of prey or threats. They also snare and haul prey into the air when weaker horizontal strands that hold them down, known as [[Guy-wire|guy lines]], break when prey thrash around.<ref name=AWV_youtube>{{cite web|title=Web Design&nbsp;... Redback Style|url=https://www.youtube.com/watch?v=tvjhc6BXQDM|publisher=Absolutely Wild Visuals|access-date=4 September 2013|date=4 July 2011|archive-date=21 September 2013|archive-url=https://web.archive.org/web/20130921064736/http://www.youtube.com/watch?v=tvjhc6BXQDM|url-status=live}}</ref> These webs are usually placed between two flat surfaces, one beneath the other.<ref>{{cite web |url=https://www.youtube.com/watch?v=bQABY9H1h1Y |title=Red Back Spider&nbsp;– Attenborough: Life in the Undergrowth |publisher=BBC Earth |author=Attenborough, David |date=28 August 2009 |access-date=4 September 2013 |archive-date=21 September 2013 |archive-url=https://web.archive.org/web/20130921064931/https://www.youtube.com/watch?v=bQABY9H1h1Y |url-status=live }}</ref> The female spends more time in the funnel and less time moving around during cooler weather.<ref name="Forster95">{{cite journal|last=Forster|first=Lyn|year=1995|title=The Behavioural Ecology of ''Latrodectus hasselti'' (Thorell), the Australian Redback Spider (Araneae: Theridiidae): a Review|journal=Records of the Western Australian Museum Supplement|volume=52|pages=13–24|issn=0313-122X}}</ref>
The individual web filaments are quite strong, able to entangle and hold small reptiles.

===Prey===
[[File:Redback vers Lizard.jpg|thumb|left|Female with a lizard it has captured]]

Redbacks usually prey on insects, but can capture larger animals that become entangled in the web, including [[trapdoor spider]]s, small [[lizard]]s,<ref name="Amo-Redback"/><ref>{{cite journal|last=Metcalfe|first=Dean C.|author2=Ridgeway, Peter A.|title=A Case of Web Entanglement and Apparent Predation of the Skink ''Lampropholis delicata'' (De Vis, 1888) (Sauria: Scincidae: Lygosominae) by the Red-back Spider ''Latrodectus hasseltii'' Thorell, 1870 (Aranea: Araneomorpha: Theridiidae) in an Autochthonous Mesic Habitat in Coastal Southeast Australia|journal=Herpetology Notes|date=23 August 2013|volume=6|pages=375–77|url=http://www.herpetologynotes.seh-herpetology.org/Volume6_PDFs/Metcalfe_HerpetologyNotes_volume6_pages375-377.pdf|access-date=24 October 2013|archive-date=29 October 2013|archive-url=https://web.archive.org/web/20131029192607/http://www.herpetologynotes.seh-herpetology.org/Volume6_PDFs/Metcalfe_HerpetologyNotes_volume6_pages375-377.pdf|url-status=dead}}</ref> and even on rare occasion snakes.<ref>{{cite web|last1=Malpass|first1=Luke|title=Spider v snake: Redback spider wins, snake dies from likely poisoning|url=http://www.smh.com.au/environment/animals/spider-v-snake-redback-spider-wins-snake-dies-from-likely-poisoning-20150303-13tgdf.html|website=The Sydney Morning Herald|access-date=3 March 2015|date=3 March 2015|archive-date=3 March 2015|archive-url=https://web.archive.org/web/20150303151220/http://www.smh.com.au/environment/animals/spider-v-snake-redback-spider-wins-snake-dies-from-likely-poisoning-20150303-13tgdf.html|url-status=live}}</ref> One web was recorded as containing a dead mouse.{{sfn|McKeown|1963|p=144}} The woodlouse (''[[Porcellio scaber]]'') is a particularly common food item.{{sfn|McKeown|1963|p=193}} Developing spiderlings need size-appropriate prey, and laboratory studies show that they are willing to consume common fruit flies (''[[Drosophila melanogaster]]''), mealworm larvae (''[[Tenebrio molitor]]''), [[Schizophora|muscoid flies]] and early nymphs of [[cockroach]]es.<ref name=Downes1987/> Food scraps and lighting attract insect prey to areas of human activity, which brings the redbacks.{{sfn|Brunet|1997|p=148}} Once alerted to a creature becoming ensnared in a trap line, the redback advances to around a leg's length from its target, touching it and squirting a liquid glutinous silk over it to immobilise it. It then bites its victim repeatedly on the head, body and leg joints and wraps it in sticky and dry silk. Unlike other spiders, it does not rotate its prey while wrapping in silk, but like other spiders, it then injects a venom that liquefies its victim's innards. Once it has trussed the prey, the redback takes it to its retreat and begins sucking out the liquefied insides, generally 5 to 20 minutes after first attacking it.<ref name="Forster95"/> Redback spiders do not usually drink, except when starved.<ref name=Forster1989/>

Commonly, [[kleptoparasitism|prey-stealing]] occurs where larger females take food items stored in other spiders' webs.<ref name="Amo-Redback"/> When they encounter other spiders of the same species, often including those of the opposite sex, they engage in battle, and the defeated spider is eaten.<ref name=SMH1907/> If a male redback is accepted by a female, it is permitted to feed on the victims snared in the female's web.<ref name=SMH1907/> Baby spiders also steal food from their mother, which she tries to prevent. They also consume sticky silk as well as small midges and flies. Spiderlings are cannibalistic, more active ones sometimes eating their less active siblings.<ref name="Forster95"/>

===Life cycle===
[[File:Baby Latrodectus hasselti cropped.jpg|thumb|right|Redback spiderlings]]
Spiderlings hatch from their eggs after about 8 days and can emerge from the egg sac as early as 11 days after being laid, although cooler temperatures can significantly slow their development so that emergence does not occur for months.<ref name=Downes1987>{{cite journal|last=Downes|first=M. F.|title=Postembryonic Development of ''Latrodectus hasselti'' Thorell (Araneae, Theridiidae)|journal=Journal of Arachnology|year=1987|volume=14|issue=3|pages=293–301|jstor=3705670}}</ref> After hatching they spend about a week inside the egg sac, feeding on the yolk and molting once.<ref name=andrade2014>{{cite journal|last1=Modanu|first1=Maria|last2=Li|first2=Lucy Dong Xuan|last3=Said|first3=Hosay|last4=Rathitharan|first4=Nizanthan|last5=Andrade|first5=Maydianne C.B.|title=Sibling cannibalism in a web-building spider: Effects of density and shared environment|journal=Behavioural Processes|volume=106|pages=12–16|doi=10.1016/j.beproc.2014.03.011|pmid=24726519|year=2014|s2cid=25968197}}</ref>  Baby spiders appear from September to January (spring to early summer).<ref name="andrade1998">{{cite journal|last=Andrade|first=Maydianne C.B.|year=1998|title=Female Hunger can Explain Variation in Cannibalistic Behavior Despite Male Sacrifice in Redback Spiders|journal=Behavioral Ecology|volume=9|issue=1|pages=33–42|doi=10.1093/beheco/9.1.33|doi-access=free}}</ref> Male spiders mature through five [[instar]]s in about 45–90 days.<ref name=Andrade2002/><ref name="andrade2002"/> Females mature through seven–eight instars in about 75–120 days.<ref name=Andrade2002/><ref name="andrade2002"/> Males live for up to six or seven months, while females may live between two and three years.<ref name="Amo-Redback"/> Laboratory tests have shown that redbacks may survive for an average of 100 days, and sometimes over 300 days without any food, those starved at {{convert|10|°C|°F|abbr=on}} faring better than those kept without food at {{convert|25|°C|°F|abbr=on}}. Spiders are known to reduce their metabolic rates in response to starvation, and can distend their abdomens to store large amounts of food.<ref name=Forster1989>{{cite journal|last=Forster|first=L. M.|author2=Kavale, J. |title=Effects of Food Deprivation on ''Latrodectus hasselti'' Thorell (Araneae: Theridiidae), the Australian Redback Spider|journal=New Zealand Journal of Zoology|date=1 July 1989|volume=16|issue=3|pages=401–08|doi=10.1080/03014223.1989.10422906|doi-access=free}}</ref><!-- cites previous two sentences --> Redbacks can survive temperatures from below freezing point to {{convert|40|°C|°F|abbr=on}}, though they do need relatively warm summers, with temperatures of {{convert|15|to|25|C|F}} for two to three months, to survive and breed.<ref name="distributions paper"/>

Redback spiderlings cohabit on the maternal web for several days to a week, during which time [[siblicide|sibling cannibalism]] is often observed.<ref name=andrade2014/> They then leave by being carried on the wind. They follow light and climb to the top of nearby logs or rocks before extending their abdomens high in the air and producing a droplet of silk.<ref name="Forster95"/> The liquid silk is drawn out into a long [[Spider silk|gossamer]] thread that, when long enough, carries the spider away. This behaviour is known as [[Ballooning (spider)|ballooning]] or kiting. Eventually, the silken thread will adhere to an object where the young spider will establish its own web.<ref name="Amo-Redback"/> They sometimes work cooperatively, climbing, releasing silk and being carried off in clusters.<ref name="Forster95"/> Juvenile spiders build webs,<ref name="andrade1998"/> sometimes with other spiders.<ref name="Forster95"/>

===Reproduction===
[[File:Latrodectus hasselti male and female.png|thumb|upright=1.5|right|Female (right) with egg sac, note the male at left (''circled'')]]
Before a juvenile male leaves its mother's web, it builds a small sperm web on which it deposits its sperm from its gonads and then collects it back into each of its two [[palp]]s (copulatory organs), because the gonads and palps are not internally connected.<ref name=Andrade2002/> After it moults into its last instar, it sets off wandering to seek a female. The male spider does not eat during this period.<ref name="andrade2002"/> How males find females is unclear, and it is possible they may balloon like juveniles.<ref name="Forster95"/> A Western Australian field study found that most males took 6 to 8 weeks to travel around {{convert|3|to|3.5|m|ft}} with occasional journeys of over {{convert|8|m|ft|abbr=on}}, but that only around 11–13% successfully found a mate.<ref name="andrade2002">{{cite journal|last=Andrade|first=Maydianne C.B.|year=2002|title=Risky mate search and male self-sacrifice in redback spiders|journal=Behavioral Ecology|volume=14|issue=4|pages=531–38|doi=10.1093/beheco/arg015|doi-access=free|hdl=1807/1012|hdl-access=free}}</ref> They are attracted by [[pheromone]]s, which are secreted by unmated sexually mature female redback spiders onto their webs and include a [[serine]] derivative (''N''-3-methylbutyryl-''O''-(''S'')-2-methylbutyryl-<small>L</small>-serine).<ref>{{cite journal|last=Jerhot|first=Elena|author2=Stoltz, Jeffrey A.|author3=Andrade, Maydianne C. B. |author4= Schulz, Stefan |title=Acylated Serine Derivatives: A Unique Class of Arthropod Pheromones of the Australian Redback Spider, ''Latrodectus hasselti''|journal=Angewandte Chemie International Edition|date=8 March 2010|volume=49|issue=11|pages=2037–40|doi=10.1002/anie.200906312|pmid=20146290|doi-access=free}}</ref> This is thought to be the sole method by which males assess a female's reproductive status, and their courtship dismantles much of the pheremone-marked web.<ref>{{cite journal|last=Stoltz|first=Jeffrey A.|author2=McNeil, Jeremy N. |author3=Andrade, Maydianne C. B. |title=Males Assess Chemical Signals to Discriminate Just-mated Females from Virgins in Redback Spiders|journal=Animal Behaviour|date=1 December 2007|volume=74|issue=6|pages=1669–74 |doi=10.1016/j.anbehav.2007.03.011|s2cid=53162873}}</ref>

During mating, the male redback attempts to copulate by inserting one of its palps into one of the female's two [[spermathecae]], each of which has its own insemination orifice. It then tries and often succeeds in inserting the other palp into the female's second orifice.<ref name=Andrade2002>{{cite journal|last=Andrade|first=Maydianne C. B.|author2=Banta, Erin M.|title=Value of Male Remating and Functional Sterility in Redback Spiders|journal=Animal Behaviour|date=May 2002|volume=63|issue=5|pages=857–70|doi=10.1006/anbe.2002.2003|s2cid=5998731}}</ref> The redback spider is one of only two animals known where the male has been found to actively assist the female in [[sexual cannibalism]]. In the process of mating, the much smaller male somersaults to place his abdomen over the female's mouthparts. In about two of three cases, the female fully consumes the male while mating continues. Males which are not eaten die of their injuries soon after mating.<ref>{{Cite journal | last1 = Forster | first1 = L. M. | doi = 10.1071/ZO9920001 | title = The Stereotyped Behavior of Sexual Cannibalism in Latrodectus-Hasselti Thorell (Araneae, Theridiidae), the Australian Redback Spider | journal = Australian Journal of Zoology | volume = 40 | pages = 1 | year = 1992 }}</ref> Sacrifice during mating is thought to confer two advantages to the species. The first is the eating process allows for a longer period of copulation and thus fertilisation of more eggs. The second is females which have eaten a male are more likely to reject subsequent males.<ref>{{cite journal | first = Maydianne C. B. | last = Andrade | date = 5 January 1996 | title = Sexual Selection for Male Sacrifice in the Australian Redback Spider | journal = Science | volume = 271 | issue = 5245 | pages = 70–72 | doi = 10.1126/science.271.5245.70 | url = http://www.utsc.utoronto.ca/~mandrade/pdf/Andrade96.pdf | bibcode = 1996Sci...271...70A | s2cid = 56279494 | access-date = 18 April 2011 | archive-date = 1 April 2011 | archive-url = https://web.archive.org/web/20110401165415/http://www.utsc.utoronto.ca/~mandrade/pdf/Andrade96.pdf | url-status = live }}</ref> Although this prohibits future mating for the males, this is not a serious disadvantage, because the spiders are sufficiently sparse that less than 20% of males ever find a potential mate during their lifetimes, and in any case, the male is functionally sterile if he has used the contents of both of his palps in the first mating.<ref name=Andrade2002/>

Some redback males have been observed using an alternative tactic that also ensures more of their genetic material is passed on. Juvenile female redbacks nearing their final moulting and adulthood have fully formed reproductive organs, but lack openings in the exoskeleton that allow access to the organs. Males will bite through the exoskeleton and deliver sperm without performing the somersault seen in males mating with adult females. The females then moult within a few days and deliver a clutch of fertilised eggs.<ref>{{cite conference |author1=Biaggio, M. D. |author2=Andrade, M. C. B. | title=Breaking an Entry: Male Redback spiders Inseminate Juvenile Females by Ripping through their Exoskeleton | work=Animal Behaviour Society meeting | date= 12–16 August 2006}}</ref><ref>{{cite journal|last=Milius|first=Susan|title=Underage Spiders: Males Show Unexpected Interest in Young Mates|journal=Science News|date=26 August 2006|volume=190|issue=9|page=133|doi=10.2307/4017121|jstor=4017121|url=http://www.sciencenews.org/view/generic/id/7690/description/Underage_Spiders_Males_show_unexpected_interest_in_young_mates|access-date=19 September 2013|archive-date=21 September 2013|archive-url=https://web.archive.org/web/20130921061440/http://www.sciencenews.org/view/generic/id/7690/description/Underage_Spiders_Males_show_unexpected_interest_in_young_mates|url-status=live|url-access=subscription}}</ref>

Once the female has mated, the sperm is stored in one or both of her spermathecae.<ref>{{cite journal|last=Snow|first=L. S. E.|author2=Andrade, M. C. B. |title=Multiple Sperm Storage Organs Facilitate Female Control of Paternity|journal=Proceedings of the Royal Society B: Biological Sciences|date=7 June 2005|volume=272|issue=1568|pages=1139–44|doi=10.1098/rspb.2005.3088|pmid=16024375|pmc=1559814}}</ref> The sperm can be used to fertilise several batches of eggs, over a period of up to two years (estimated from observations of closely related species),<ref name=Andrade2002/><ref>{{cite journal|last=Kaston|first=B. J.|title=Comparative Biology of American Black Widow Spiders|journal=Transactions of the San Diego Society of Natural History|year=1970|volume=16|issue=3|pages=33–82 |url=https://archive.org/stream/cbarchive_125679_comparativebiologyofamericanbl1905/comparativebiologyofamericanbl1905}}</ref>  but typically restarts the female's pheromone production advertising her sexual availability about three months after mating.<ref>{{cite journal|last=Perampaladas|first=Kuhan|author2=Stoltz, J. A. |author3=Andrade, M. C. B. |title=Mated Redback Spider Females Re-Advertise Receptivity Months after Mating|journal=Ethology|date=1 June 2008|volume=114|issue=6|pages=589–98|doi=10.1111/j.1439-0310.2008.01513.x|bibcode=2008Ethol.114..589P }}</ref> A female spider may lay four to ten egg sacs,<ref name="Species bank"/> each of which is around {{convert|1|cm|in|abbr=on}} in diameter and contains on average around 250 eggs,<ref name="Amo-Redback"/> though can be as few as 40 or as many as 500.<ref name="Species bank"/> She prepares a shallow concave disc around {{convert|3|mm|in|frac=8|abbr=on}} in diameter before laying eggs into it over a period of around five minutes before laying more silk to complete the sac, which becomes spherical, the whole process taking around one and a quarter hours.{{sfn|McKeown|1963|pp=190–91}} She can produce a new egg sac as early as one to three weeks after her last.<ref name="Amo-Redback"/>

==Distribution and habitat==
[[File:Redback spider records map.png|thumb|A distribution map of the records of redback spider specimens reported to the [[Atlas of Living Australia]] as of September 2013.]]
The redback spider is widespread across Australia. The current distribution reported by the World Spider Catalogue includes Southeast Asia and New Zealand.<ref name=WSC_s39048/> Colonies and individuals have been found elsewhere, including Japan,<ref>{{Cite news|url=https://www.independent.co.uk/life-style/health-and-families/health-news/venomous-aussie-redback-spiders-invading-japan-5508922.html|title=Venomous Aussie redback spiders invading Japan|date=25 November 2009|work=The Independent|access-date=30 March 2018|language=en-GB|archive-date=30 March 2018|archive-url=https://web.archive.org/web/20180330081529/https://www.independent.co.uk/life-style/health-and-families/health-news/venomous-aussie-redback-spiders-invading-japan-5508922.html|url-status=live}}</ref><ref>{{Cite news|url=http://www.abc.net.au/news/2014-10-20/redback-spiders-found-for-the-first-time-in-tokyo/5827612|title=Redback spiders found in Tokyo for first time|date=20 October 2014|work=ABC News|access-date=30 March 2018|language=en-AU|archive-date=4 January 2021|archive-url=https://web.archive.org/web/20210104063414/https://www.abc.net.au/news/2014-10-20/redback-spiders-found-for-the-first-time-in-tokyo/5827612|url-status=live}}</ref> England, Belgium, the United Arab Emirates and Iran.<ref name=WhytAnde17/><ref name="distributions paper" /><ref name="Slaughter" /><ref name="MAF" /> It was believed at one time that the redback may have been introduced to Australia, because when it was first formally described in 1870, it appeared to be concentrated around sea ports.<ref name="garb 2004">{{cite journal|last=Garb|first=Jessica E.|author2=González, Alda|author3=Gillespie, Rosemary G.|title=The Black Widow Spider Genus ''Latrodectus'' (Araneae: Theridiidae): Phylogeny, Biogeography, and Invasion History|journal=Molecular Phylogenetics and Evolution|date=June 2004|volume=31|issue=3|pages=1127–42|doi=10.1016/j.ympev.2003.10.012|url=http://nature.berkeley.edu/~gillespie/Publications_files/GarbGonzGillMPE.pdf|pmid=15120405|bibcode=2004MolPE..31.1127G |access-date=9 September 2013|archive-date=21 September 2013|archive-url=https://web.archive.org/web/20130921060650/http://nature.berkeley.edu/~gillespie/Publications_files/GarbGonzGillMPE.pdf|url-status=live}}</ref><ref name=RaveGall87>{{Cite book |last1=Raven |first1=R.J. |last2=Gallon |first2=J.A. |date=1987 |editor1-last=Covacevich |editor1-first=J. |editor2-last=Davie |editor2-first=P. |editor3-last=Pearns |editor3-first=J. |contribution=The redback spider |title=Toxic Plants and Animals : A Guide for Australia |pages=307–11 |location=Brisbane |publisher=Queensland Museum |name-list-style=amp }}</ref> However, an earlier informal description (1850) from the Adelaide Hills is now known, and names in [[Australian Aboriginal languages]] also show that it was present well before European settlement. Its original range is thought to be a relatively small arid part of South Australia and Western Australia.<ref name=WhytAnde17>{{Cite book |last1=Whyte |first1=Robert |last2=Anderson |first2=Greg |date=2017 |title=A Field Guide to Spiders of Australia |publisher=CSIRO Publishing |isbn=978-0-643-10707-6 |name-list-style=amp }} p. 339.</ref> Its spread has been inadvertently aided by modern buildings, which often provide habitats conducive to redback populations.{{sfn|Brunet|1997|p=148}} The close relationship between the redback and the New Zealand [[katipō]] also supports the native status of both in their respective countries.<ref name="Forster95"/>

Outside urban areas, the redback is more often found in drier habitats ranging from [[sclerophyll]] forest to desert, even as harsh as the [[Simpson Desert]].{{sfn|Brunet|1997|p=148}} It became much more common in urban areas in the early decades of the 20th century,{{sfn|McKeown|1963|p=188}} and is now found in all but the most inhospitable environments in Australia and its cities.{{sfn|Brunet|1997|p=148}} It is particularly common in [[Brisbane]], [[Perth]] and [[Alice Springs]].<ref name=Nimorakiotakis>{{cite journal|author1=Nimorakiotakis, B.|author2=Winkel, K.D.|year=2004|title=Spider bite – the redback spider and its relatives|url=http://www.racgp.org.au/afpbackissues/2004/200403/20040311winkel.pdf|journal=Australian Family Physician|volume=33|issue=3|pages=153–57|pmid=15054982|access-date=18 October 2013|archive-date=19 October 2013|archive-url=https://web.archive.org/web/20131019144016/http://www.racgp.org.au/afpbackissues/2004/200403/20040311winkel.pdf|url-status=live}}</ref> It is wide spread throughout urban Australia, with most suburban backyards in the city of Canberra (for instance) having one or more nesting females in such places as firewood piles, stored brick stacks and around unused or restoring motor vehicles as well as generally behind the shed - as observed since at least the 1970s and probably earlier. The redback spider is commonly found in close proximity to human residences. Webs are usually built in dry, dark, sheltered sites, such as among rocks, in logs, tree hollows, shrubs, old tyres, sheds, outhouses, empty tins and boxes, children's toys or under rubbish or litter.<ref name=SMH1907/><ref name="Amo-Redback"/><ref name="autogenerated3">{{cite news |url=http://nla.gov.au/nla.news-article39366487 |title=Beware the Red-Back spider. |newspaper=[[Western Mail (Western Australia)|Western Mail]] |location=Perth |date=18 March 1954 |page=3 |publisher=National Library of Australia |access-date=4 September 2013 |archive-date=19 October 2021 |archive-url=https://web.archive.org/web/20211019062747/https://trove.nla.gov.au/newspaper/article/39366487 |url-status=live }}</ref> Letterboxes and the undersurface of toilet seats are common sites.{{sfn|Brunet|1997|p=148}} Populations can be controlled by clearing these habitats,<ref name=CentralianAdvocate/> squashing the spiders and their egg sacs,<ref name=Warden1989/> and using pesticide in outhouses.<ref name=CentralianAdvocate>{{cite news |url=http://nla.gov.au/nla.news-article59838671 |title=Redback Plague Continues. |newspaper=Centralian Advocate |location=Alice Springs, NT |date=26 January 1951 |page=13 |publisher=National Library of Australia |access-date=4 September 2013 |archive-date=19 October 2021 |archive-url=https://web.archive.org/web/20211019062748/https://trove.nla.gov.au/newspaper/article/59838671 |url-status=live }}</ref> The [[Commonwealth Scientific and Industrial Research Organisation|CSIRO]] Division of Entomology recommends against the use of spider pesticides due to their toxicity, and because redbacks are rapid recolonists anyway.<ref name=Warden1989/>

Spiders in the French territory of [[New Caledonia]] in the Pacific were identified as ''L. hasselti'' in 1920, based on morphology. Their behaviour differs from Australian redbacks, as they do not engage in sexual cannibalism and are less prone to biting humans. The first recorded [[envenomation]] in New Caledonia was in 2007.<ref name=Maillaud>{{cite journal|last=Maillaud|first=Claude|author2=Jourdan, Hervé |author3=Winkel, Ken |author4=Arnaud, Gaëlle |author5=Lafforgue, Patrick |author6= Durand, Francis |title=Latrodectism in New Caledonia: First Report of Presumed Redback Spider (''Latrodectus hasselti'') Envenomation|journal=Wilderness & Environmental Medicine|date=1 December 2009|volume=20|issue=4|pages=339–43|doi=10.1580/1080-6032-020.004.0339|pmid=20030441|doi-access=free}}</ref>

===Introductions===
The redback spider's affinity for human-modified habitat has enabled it to spread to several countries via international shipping and trade. Furthermore, its tolerance to cold means that it has the ability to colonise many temperate countries with a winter climate cooler than Australia. This is concerning due to the risks to people being bitten who are unaware of its venomous nature, and also to the conservation of local threatened insect species that the redback might prey upon.<ref name="distributions paper"/>

Redback spiders are also found in small colonies in areas of New Zealand. They are frequently intercepted by quarantine authorities, often among steel or car shipments.<ref name="distributions paper">{{Cite journal | last1 = Vink | first1 = C. J. | last2 = Derraik | first2 = J. G. B. | last3 = Phillips | first3 = C. B. | last4 = Sirvid | first4 = P. J. | title = The Invasive Australian Redback Spider, ''Latrodectus hasseltii'' Thorell 1870 (Araneae: Theridiidae): Current and Potential Distributions, and Likely Impacts | doi = 10.1007/s10530-010-9885-6 | journal = Biological Invasions | volume = 13 | issue = 4 | pages = 1003–19 | year = 2010 | s2cid = 1887942 }}</ref> They were introduced into New Zealand in the early 1980s,<ref>{{citeQ|Q130183406}}</ref> and now are found around Central [[Otago]] (including [[Alexandra, New Zealand|Alexandra]], [[Bannockburn, New Zealand|Bannockburn]] and near [[Wānaka]]) in the South Island and [[New Plymouth]] in the North Island.<ref name="distributions paper"/><ref name="Slaughter"/><ref name="MAF">{{cite report |author1=Reed, C. |author2=Newland, S. |author3=Downs, J. |author4=Forbes, V. |author5=Gilbert, S. |title=MAF Biosecurity Pest Risk Assessment: Spiders Associated With Table Grapes From United States of America (State of California), Australia, Mexico and Chile |publisher=MAF Biosecurity |date=September 2002 |url=http://www.biosecurity.govt.nz/files/regs/imports/risk/spiders-grapes-ra.pdf |access-date=18 February 2007 |archive-url=https://web.archive.org/web/20100523183538/http://www.biosecurity.govt.nz/files/regs/imports/risk/spiders-grapes-ra.pdf |archive-date=23 May 2010 |url-status=dead  }}</ref> Authorities in the United Arab Emirates warn residents and visitors of redback spiders, which have been present since 1990.<ref>{{cite web|url=http://gulfnews.com/news/gulf/uae/environment/redback-spiders-are-back-don-t-panic-urges-dubai-municipality-1.1155440|title=Redback Spiders are Back: Don't Panic, urges Dubai Municipality|first=Mariam M.|last=Al Serkal|date=7 March 2013|access-date=1 September 2013|archive-date=27 September 2013|archive-url=https://web.archive.org/web/20130927121939/http://gulfnews.com/news/gulf/uae/environment/redback-spiders-are-back-don-t-panic-urges-dubai-municipality-1.1155440|url-status=live}}</ref> Colonies have also been established in greenhouses in Belgium{{cn|date=April 2025}}, and isolated observations indicate possible presence in [[New Guinea]], the Philippines, and India.<ref name="distributions paper"/> Some redbacks were found in [[Preston, Lancashire]], England, after a container of parts<!--what kind of parts?--> arrived from Australia; some may have escaped into the countryside before pest controllers could destroy them.<ref name="Metro">{{cite web | publisher= Metro | title= Deadly Australian Spiders 'invading' the UK, one Field at a Time | url= http://www.metro.co.uk/weird/832600-deadly-australian-spiders-invading-the-uk-one-step-at-a-time | date= 24 June 2010 | access-date= 24 June 2010 | archive-date= 26 June 2010 | archive-url= https://web.archive.org/web/20100626002010/http://www.metro.co.uk/weird/832600-deadly-australian-spiders-invading-the-uk-one-step-at-a-time | url-status= live }}</ref> One redback was found in a back garden in [[Borough of Dartford|Dartford]] in [[Kent]].<ref name='Kent"2014"'>{{cite news|last1=Clarke-Billings|first1=Lucy|title=Deadly spider that can kill with one bite found in a back garden in KENT|url=https://www.mirror.co.uk/news/uk-news/deadly-spider-can-kill-one-4715326|access-date=28 November 2014|work=Daily Mirror|date=28 November 2014|archive-date=28 November 2014|archive-url=https://web.archive.org/web/20141128231625/http://www.mirror.co.uk/news/uk-news/deadly-spider-can-kill-one-4715326|url-status=live}}</ref> Two females were discovered in the Iranian port city of [[Bandar Abbas]] in 2010.<ref>{{cite journal|author1=Shahi, M. |author2=Hosseini, A. |author3=Shemshad, K. |author4=Rafinejad, J. |year=2011|title=The Occurrence of Red-Back Spider Latrodectus hasselti (Araneae: Theridiidae) in Bandar Abbas, Southern Part of Iran|journal= Journal of Arthropod-Borne Diseases |volume=5|issue=1|pages=63–68|pmid=22808411 |pmc=3385565 |url=http://journals.tums.ac.ir/full_text.aspx?org_id=59&culture_var=en&journal_id=20&issue_id=2289&manuscript_id=18843&segment=en|archive-url=https://web.archive.org/web/20131019130429/http://journals.tums.ac.ir/full_text.aspx?org_id=59&culture_var=en&journal_id=20&issue_id=2289&manuscript_id=18843&segment=en|archive-date=19 October 2013 }}</ref>

There is an established population of redback spiders in [[Osaka]], Japan,<ref name="distributions paper"/><ref>{{cite journal|last=Ori|first=Masahisa|author2=Shinkai, Eiichi|author3=Ikeda, Hiroyoshi|title=Introduction of Widow Spiders into Japan|journal=Medical Entomology and Zoology|year=1996|volume=47|issue=2|pages=111–19|language=ja|doi=10.7601/mez.47.111|doi-access=free}}</ref><ref name=nihei>{{Cite journal | last1 = Nihei | first1 = N. | last2 = Yoshida | first2 = M. | last3 = Kaneta | first3 = H. | last4 = Shimamura | first4 = R. | last5 = Kobayashi | first5 = M. | title = Analysis on the Dispersal Pattern of Newly Introduced ''Latrodectus hasseltii'' (Araneae: Theridiadae) in Japan by Spider Diagram | doi = 10.1603/0022-2585-41.3.269 | journal = Journal of Medical Entomology | volume = 41 | issue = 3 | pages = 269–76 | year = 2004 | pmid =  15185925| s2cid = 6939079 | doi-access = free }}</ref> thought to have arrived in cargoes of wood chips.<ref name="Vic">{{cite web | author= Victoria Museum | title= Redback Spider | url= http://www.museum.vic.gov.au/spidersparlour/spider13.htm | access-date= 18 February 2007 | archive-date= 27 January 2007 | archive-url= https://web.archive.org/web/20070127012926/http://www.museum.vic.gov.au/spidersparlour/spider13.htm | url-status= live }}</ref>
In 2008, redback spiders were found in [[Fukuoka]], Japan. Over 700 have been found near the container terminal in [[Hakata Bay]], Fukuoka City.<ref name="xinhuanet1">{{cite web |url=http://news.xinhuanet.com/english/health/2012-12/26/c_132065195.htm |title=Japan's Fukuoka Wipes Out over 4,600 Poisonous Red-back Spiders |website=News.xinhuanet.com |date=26 December 2012 |access-date=4 September 2013 |url-status=dead |archive-url=https://web.archive.org/web/20130925195744/http://news.xinhuanet.com/english/health/2012-12/26/c_132065195.htm |archive-date=25 September 2013  }}</ref> Dispersal mechanisms within Japan are unclear, but redbacks are thought to have spread by walking or by being carried on vehicles.<ref name=nihei/> In September 2012, after being bitten a woman was hospitalised in the Higashi Ward of Fukuoka City.<ref name="FukuokaNow">{{cite web | work= Fukuoka Now | title= Woman Bitten by Deadly Redback Spider | url= http://fukuoka-now.com/news/woman-bitten-by-deadly-redback-spider/ | access-date= 6 September 2012 | archive-date= 9 September 2012 | archive-url= https://web.archive.org/web/20120909181756/http://fukuoka-now.com/news/woman-bitten-by-deadly-redback-spider/ | url-status= live }}</ref> Signs warning about redback spiders have been posted in parks around the city.<ref name="xinhuanet1"/>

==Predators and parasitoids==
The black house spider (''[[Badumna insignis]]''), the cellar spider (''[[Pholcus phalangioides]]'') and the giant daddy-long-legs spider (''[[Artema atlanta]]'') are known to prey on the redback spider,<ref>{{cite web|title=Redback Spider|url=http://www.qm.qld.gov.au/Find+out+about/Animals+of+Queensland/Spiders/Modern+Spiders+Infraorder+Araneomorphae/Redback+and+Brown+Widow+spiders/Redback+Spider|publisher=[[Queensland Museum]]|access-date=5 September 2013|archive-date=1 September 2013|archive-url=https://web.archive.org/web/20130901163328/http://www.qm.qld.gov.au/Find+out+about/Animals+of+Queensland/Spiders/Modern+Spiders+Infraorder+Araneomorphae/Redback+and+Brown+Widow+spiders/Redback+Spider|url-status=live}}</ref> and redbacks are often absent if these species are present in significant numbers.{{sfn|Sutherland|Tibballs|2001|p=387}}  ''[[Agenioideus nigricornis]]'', a [[spider wasp]], is a [[parasitoid]] of the adult redback.<ref name=Krogmann/> Other [[Hymenoptera|wasps]] of the families [[Eurytomidae]] and [[Ichneumonidae]] parasitise redback eggs, and mantid lacewings ([[Mantispidae]]) prey on redback eggs.<ref name=Krogmann>{{cite journal |last1=Krogmann |first1=Lars |last2=Austin |first2=Andrew D.|year=2011 |title=Systematics of Australian ''Agenioideus'' Ashmead (Hymenoptera: Pompilidae) with the First Record of a Spider Wasp Parasitizing ''Latrodectus hasselti'' Thorell (redback spider) |journal=Australian Journal of Entomology |volume=51 |issue=3 |pages=166–74 |doi=10.1111/j.1440-6055.2011.00850.x|doi-access=free }}</ref>

==Bites to humans==

===Incidence===
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.{{sfn|White|2013|p=203}}<ref>{{Cite journal|date=8 August 2017|title=Redback Spider Envenomation: Background, Pathophysiology, Epidemiology|url=https://emedicine.medscape.com/article/772484-overview#a6|website=emedicine.medscape.com|access-date=22 October 2017|archive-date=23 October 2017|archive-url=https://web.archive.org/web/20171023064046/https://emedicine.medscape.com/article/772484-overview#a6|url-status=live}}</ref> Estimates of the number of people thought to be bitten by redback spiders each year across Australia range from 2,000 to 10,000.<ref name=Nicholson2003/><ref name=White1998/> 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 its being incapable of biting or lacking potent venom.<ref name="isbister"/><!--cites 13sentences--> The bite from both juvenile and mature females appears to have similar potency. The male bite usually only produces short-lived, mild pain.<ref name="isbister"/><!--cites 2 sentences--> Most bites occur in the warmer months between December and April, in the afternoon or evening.<ref name="isbister">{{cite journal|last=Isbister|first=Geoffrey K.|author2=Gray, Michael R.|title=Latrodectism: a Prospective Cohort Study of Bites by Formally Identified Redback Spiders|journal=Medical Journal of Australia|volume=179|issue=2|pages=88–91|year=2003|pmid=12864719|url=https://www.mja.com.au/journal/2003/179/2/latrodectism-prospective-cohort-study-bites-formally-identified-redback-spiders|type=Prospective cohort study|doi=10.5694/j.1326-5377.2003.tb05442.x|s2cid=25632248|access-date=3 September 2013|archive-date=21 September 2013|archive-url=https://web.archive.org/web/20130921060129/https://www.mja.com.au/journal/2003/179/2/latrodectism-prospective-cohort-study-bites-formally-identified-redback-spiders|url-status=live|url-access=subscription}}</ref><!--cites 1 sentences--><ref name="sutherland">{{cite journal |author1=Sutherland, S. |author2=Trinca, J. |title=Survey of 2144 Cases of Redback Spider Bites: Australia and New Zealand, 1963–1976 |journal=Medical Journal of Australia |volume=2 |issue=14 |pages=620–23 |year=1978 |pmid=732670 |type=Case report |doi=10.5694/j.1326-5377.1978.tb131783.x |s2cid=22729861 }}</ref> 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.{{sfn|Sutherland|Tibballs|2001|p=393}}<ref name=Ibister2004/>

A 2004 review reported 46% of bites occurring on [[Anatomical terms of location#Proximal and distal|distal]] extremities of the limbs, 25% on [[Anatomical terms of location#Proximal and distal|proximal areas of limbs]] (upper arms and thighs), 21% on the trunk, and 7% on the head or neck.<ref name=Ibister2004/> In some cases the same spider bites a victim multiple times.<ref>{{cite news |url=http://nla.gov.au/nla.news-article122074552 |title=Spider Bite Proves Fatal. |newspaper=[[Queensland Times]] |location=Ipswich (Qld.) |date=26 February 1940 |page=6 Edition: Daily |publisher=National Library of Australia |access-date=5 September 2013 |archive-date=19 October 2021 |archive-url=https://web.archive.org/web/20211019062748/https://trove.nla.gov.au/newspaper/article/122074552 |url-status=live }}</ref><ref>{{cite news |url=http://nla.gov.au/nla.news-article98108718 |title=General News. Bitten by Redback Spider |newspaper=Western Star and Roma Advertiser |location=Toowoomba, Qld. |date=25 March 1936 |page=2 |publisher=National Library of Australia |access-date=5 September 2013 |archive-date=19 October 2021 |archive-url=https://web.archive.org/web/20211019062749/https://trove.nla.gov.au/newspaper/article/98108718 |url-status=live }}</ref> Historically, victims were often bitten on the genitalia, though this phenomenon disappeared as [[outhouse]]s were superseded by plumbed indoor toilets.<ref name="jelinek1997" /><ref>{{cite news|last=McIlraith|first=Shaun|title=Redbacks Giving Way to Progress|url=https://news.google.com/newspapers?id=RgMRAAAAIBAJ&dq=redback%20shoes%20spider&pg=2821%2C446841|newspaper=[[Sydney Morning Herald]]|date=4 January 1979|page=3|access-date=27 August 2020|archive-date=19 October 2021|archive-url=https://web.archive.org/web/20211019062747/https://news.google.com/newspapers?id=RgMRAAAAIBAJ&dq=redback+shoes+spider&pg=2821%2C446841|url-status=live}}</ref> Conversely, bites on the head and neck have increased with use of safety helmets and ear muffs.{{sfn|Sutherland|Tibballs|2001|p = 393}} 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.<!-- refs for two sentences in this paragraph --><ref>{{cite web|url=https://australian.museum/learn/animals/spiders/spiders-in-the-house-and-garden/|title=Spiders in the House and Garden|author=Australian Museum|date=6 May 2013|work=Nature Culture Discover|publisher=Australian Museum|access-date=25 October 2013|location=Sydney, New South Wales|archive-date=6 July 2020|archive-url=https://web.archive.org/web/20200706174623/https://australian.museum/learn/animals/spiders/spiders-in-the-house-and-garden/|url-status=live}}</ref><ref>{{cite web|url=http://www.betterhealth.vic.gov.au/bhcv2/bhcarticles.nsf/pages/Spiders|title=Spiders|author=Department of Health|date=10 September 2013|work=Better Health Channel|publisher=State Government of Victoria|access-date=25 October 2013|url-status=dead|archive-url=https://web.archive.org/web/20131029203227/http://www.betterhealth.vic.gov.au/bhcv2/bhcarticles.nsf/pages/Spiders|archive-date=29 October 2013}}</ref>

===Venom===
{{Main|Latrotoxin}}
[[File:Latrodectus hasselti -Sydney, Australia-8.jpg|thumb|right|The distinctive red stripe of the adult female]]
The redback and its relatives in the genus ''Latrodectus'' are considered dangerous, alongside funnel-web spiders (''[[Atrax]]'' and ''[[Hadronyche]]''), mouse spiders (''[[Missulena]]''), wandering spiders (''[[Phoneutria]]'') and recluse spiders (''[[Loxosceles]]'').<ref name="Amo-Redback1">{{cite web | author=Australian Museum | title=Spider Facts | url=https://australian.museum/learn/animals/spiders/spider-facts/ | access-date=20 September 2013 | date=6 May 2013 | archive-date=13 July 2020 | archive-url=https://web.archive.org/web/20200713060040/https://australian.museum/learn/animals/spiders/spider-facts/ | url-status=live }}</ref><ref>{{cite journal|last=Espino-Solis|first=G.P.|author2=Riaño-Umbarila, L. |author3=Becerril, B. |author4= Possani, L.D. |title=Antidotes against Venomous Animals: State of the Art and Prospectives|journal=Journal of Proteomics|date=6 March 2009|volume=72|issue=2|pages=183–99|doi=10.1016/j.jprot.2009.01.020|pmid=19457345|type=Review}}</ref> Venom is produced by [[holocrine]] glands in the spider's [[chelicerae]] (mouth parts).<ref name=Rohou2007>{{cite journal |title=Insecticidal Toxins from Black Widow Spider Venom |date=15 March 2007|journal=Toxicon |volume=49 |pages=531–49 |first1= A |last1=Rohou |first2= J |last2=Nield |first3= Y.A. |last3=Ushkaryov|pmc=2517654 |issue=4–5 |doi=10.1016/j.toxicon.2006.11.021|pmid=17210168 |bibcode=2007Txcn...49..531R |type=Review }}</ref> Venom accumulates in the lumen of the glands and passes through paired ducts into the spider's two hollow fangs.<ref name=Rohou2007/><ref name="NicholsonGraudins"/> 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, [[enzyme]]s and a number of high-molecular-weight toxins, including insect toxins and a vertebrate [[neurotoxin]] called [[alpha-latrotoxin]], which causes intense pain in humans.<ref name=Rohou2007/><ref name="NicholsonGraudins">{{cite journal|last1=Nicholson|first1=Graham M.|last2=Graudins|first2=Andis|title=Spiders of Medical Importance in the Asia-Pacific: Atracotoxin, Latrotoxin and Related Spider Neurotoxins|journal=Clinical and Experimental Pharmacology and Physiology|volume=29|issue=9|year=2002|pages=785–94|issn=0305-1870|pmid= 12165044| doi=10.1046/j.1440-1681.2002.03741.x|s2cid=12620544|type=Review}}</ref>

In [[vertebrates]], alpha-latrotoxin produces its effect through destabilisation of [[cell membrane]]s and [[degranulation]] of [[nerve|nerve terminals]], resulting in excessive release of [[neurotransmitter]]s, namely [[acetylcholine]], [[norepinephrine]] and [[Gamma-aminobutyric acid|GABA]]. Excess neurotransmitter activity leads to clinical manifestations of envenomation,<ref name="White">{{cite book | editor1 = Meier, J. | editor2 = White, J. | title = Handbook of Clinical Toxicology of Animal Venoms and Poisons | year = 1995 | publisher = CRC Press | url = http://www.toxinology.com/fusebox.cfm?staticaction=generic_static_files/toxdept_crcbook.html | isbn = 0-8493-4489-1 | access-date = 19 October 2021 | archive-date = 12 June 2018 | archive-url = https://web.archive.org/web/20180612141017/http://www.toxinology.com/fusebox.cfm?staticaction=generic_static_files%2Ftoxdept_crcbook.html | url-status = live }}</ref> although the precise mechanisms are not well understood.<ref name=Nimorakiotakis/> Acetylcholine release accounts for neuromuscular manifestations, and norepinephrine release accounts for the cardiovascular manifestations.<ref>{{Cite web|url=http://accessmedicine.mhmedical.com.acs.hcn.com.au/content.aspx?bookid=1658&sectionid=109385845|title=MedicalDirector Login|website=accessmedicine.mhmedical.com.acs.hcn.com.au|access-date=23 October 2017|archive-date=19 October 2021|archive-url=https://web.archive.org/web/20211019062752/https://acs.hcn.com.au/ksLicensing/auth0/institution?redirectURL=http%3A%2F%2Faccessmedicine.mhmedical.com.acs.hcn.com.au%2Fcontent.aspx%3Fbookid%3D1658%26sectionid%3D109385845|url-status=live}}</ref> Female redbacks have an average of around 0.08–0.10&nbsp;mg of venom, and experiments indicate that the [[median lethal dose]] (LD<sub>50</sub>) for mice at room temperature is 10–20% of this quantity (0.27–0.91&nbsp;mg/kg based on the mass of the mice used), but that it is considerably deadlier for mice kept at lower or higher temperatures.<ref name=Wiener1956Temperature>{{cite journal|last=Wiener|first=Saul|title=The Australian Red Back Spider (''Latrodectus Hasseltii''): II. Effect of Temperature on the Toxicity of Venom|journal=The Medical Journal of Australia|date=1 September 1956|volume=43|issue=9|pages=331–34|doi=10.5694/j.1326-5377.1956.tb56713.x|pmid=13368800|s2cid=44645205}}</ref> Pure alpha-latrotoxin has an LD<sub>50</sub> in mice of 20–40&nbsp;μg/kg.<ref>{{cite web|last=Rubin|first=Rebecca L.|title=Redback Spider Envenomation|url=http://emedicine.medscape.com/article/772484-overview#showall|work=Medscape Reference|publisher=WebMD LLC|access-date=16 October 2013|author2=Wiener, Sage W.|date=16 April 2012|archive-date=16 October 2013|archive-url=https://web.archive.org/web/20131016115138/http://emedicine.medscape.com/article/772484-overview#showall|url-status=live}}</ref>

The specific variant of the vertebrate toxin found in the redback was cloned and sequenced in 2012, and was found to be a sequence of 1180 [[amino acid]]s,<ref name=graudins2012>{{cite journal|last=Graudins|first=Andis|author2=Little, Michelle J. |author3=Pineda, Sandy S. |author4=Hains, Peter G. |author5=King, Glenn F. |author6=Broady, Kevin W. |author7= Nicholson, Graham M. |title=Cloning and Activity of a Novel α-latrotoxin from Red-back Spider Venom|journal=Biochemical Pharmacology|date=1 January 2012|volume=83|issue=1|pages=170–83|doi=10.1016/j.bcp.2011.09.024|pmid=22001442|type=Comparative study|hdl=10453/18571|hdl-access=free}}</ref> with a strong similarity to the equivalent molecule across the ''Latrodectus mactans'' clade.<ref>{{cite journal|last=Garb|first=J. E.|author2=Hayashi, C. Y. |title=Molecular Evolution of α-Latrotoxin, the Exceptionally Potent Vertebrate Neurotoxin in Black Widow Spider Venom|journal=Molecular Biology and Evolution|date=21 January 2013|volume=30|issue=5|pages=999–1014|doi=10.1093/molbev/mst011|pmid=23339183|pmc=3670729}}</ref> The syndromes caused by bites from any spiders of the genus ''Latrodectus'' have similarities;<ref>{{cite journal|last=Maretić|first=Zvonimir|year=1983|title=Latrodectism: Variations in Clinical Manifestations Provoked by ''Latrodectus'' Species of Spiders |journal=Toxicon|volume=21|issue=4|pages=457–66|doi=10.1016/0041-0101(83)90123-X|pmid=6353667|bibcode=1983Txcn...21..457M |type=Review}}</ref> there is some evidence there is a higher incidence of sweating, and local and radiating pain with the redback, while black widow envenomation results in more back and abdominal pain,<ref name="jelinek1997">{{cite journal|last=Jelinek|first=George A. |title=Widow Spider Envenomation (Latrodectism): a Worldwide Problem|journal=Wilderness & Environmental Medicine|year=1997 |volume=8|issue=4|pages=226–31|pmid=11990169|doi=10.1580/1080-6032(1997)008[0226:WSELAW]2.3.CO;2|type=Review|doi-access=free}}</ref> and abdominal rigidity is a feature common with bites from the west coast button spider (''[[Button spider|Latrodectus indistinctus]]'') of South Africa.<ref name="lancet"/>

One crustacean-specific and two insect-specific neurotoxins have been recovered from the [[Mediterranean black widow]] (''L. tredecimguttatus''), as have small [[peptide]]s that inhibit [[Angiotensin-converting enzyme|angiotensin-1-converting enzyme]];{{efn|These likely make the venom stronger by altering the victim's physiology.<ref name="vassilevski">{{cite journal|author1=Vassilevski, A. A.|author2=Kozlov, S. A.|author3=Grishin, E. V.|year=2009|title=Molecular Diversity of Spider Venom|journal=Biochemistry (Moscow)|volume=74|issue=13|pages=1505–34|url=http://protein.bio.msu.ru/biokhimiya/contents/v74/pdf/bcm_1505.pdf|doi=10.1134/S0006297909130069|pmid=20210706|s2cid=24572908|access-date=17 November 2013|archive-date=28 September 2010|archive-url=https://web.archive.org/web/20100928080451/http://protein.bio.msu.ru/biokhimiya/contents/v74/pdf/bcm_1505.pdf|url-status=live}}</ref> Angiotensin-converting-enzyme inhibitors, or [[ACE inhibitor]]s, are a class of widely-prescribed medications used in [[hypertension]] and [[heart failure]].<ref>{{cite journal|last=Sweitzer|first= Nancy K. |year=2003|title=What Is an Angiotensin Converting Enzyme Inhibitor?|journal=Circulation|volume=108|pages=e16–18|doi=10.1161/01.CIR.0000075957.16003.07|pmid= 12876137 |issue=3|doi-access=free}}</ref>

}} the venom of the redback, although little-studied, likely has similar agents.<ref name=graudins2012/>{{sfn|Sutherland|Tibballs|2001|p=390}}

===Antivenom===
[[File:F ab2 pFc.png|thumb|An [[antibody]] digested by [[pepsin]] yields two fragments: a [[F(ab')2|F(ab')<sub>2</sub>]] fragment and a pFc' fragment. Redback spider [[antivenom]] contains purified F(ab')<sub>2</sub> derived from [[IgG]] in hyperimmune horse [[Plasma (blood)|plasma]].<ref name=cmg2007>{{cite web|url=http://www0.health.nsw.gov.au/archive/policies/gl/2007/pdf/GL2007_006.pdf |title=Snakebite & Spiderbite Clinical Management Guidelines 2007 – NSW |publisher=Department of Health, NSW |page=47 |date=17 May 2007 |access-date=10 November 2013}}</ref><!--ref for last sentence only-->]]
{{Further|Antivenom}}
Redback antivenom was developed by [[CSL Limited|Commonwealth Serum Laboratories]], then a government body involved with discovering antivenoms for many venomous Australian creatures. Production involves the milking of venom from redbacks and repeatedly inoculating horses with non-lethal doses. The horse [[immune system]]s makes polyclonal [[antibody|antibodies]].<ref>{{cite web|url=http://www.powerhousemuseum.com/australia_innovates/?behaviour=view_article&Section_id=1030&article_id=10026|title=CSL antivenoms|author=ATSE project team|year=2001|work=Australia Innovates|publisher=Powerhouse Museum|access-date=9 October 2013|location=Haymarket, New South Wales|archive-date=7 August 2016|archive-url=https://web.archive.org/web/20160807152107/http://www.powerhousemuseum.com/australia_innovates/?behaviour=view_article&Section_id=1030&article_id=10026|url-status=live}}</ref> [[Blood plasma]], containing the antibodies, is extracted by [[plasmapheresis]].<ref>{{cite web|url=http://www.aomevents.com/media/files/AIMS%20NZIMLS%20SPC/Prowse.pdf |title=Antivenom Improvements |first=Claire |last=Prowse |publisher=aomevents.com |archive-url=https://web.archive.org/web/20131110170051/http://www.aomevents.com/media/files/AIMS%20NZIMLS%20SPC/Prowse.pdf|archive-date=10 November 2013 |access-date=10 November 2013}}</ref> The plasma is treated with [[pepsin]], and the active [[F(ab')2|F(ab')<sub>2</sub>]] fragments are separated and purified.<ref>{{cite book|url=https://books.google.com/books?id=BfdighlyGiwC&q=antivenom+redback+spider+pepsin&pg=PA262 |title=Medical Toxicology |author= Seifert, Stephen A |editor=Dart, Richard C|publisher=Lippincott Williams & Wilkins |edition=3rd |page=262 |year=2004|isbn=978-0-7817-2845-4}}</ref> Each vial contains 500 units of redback antivenom in approximately 1.5 ml,<ref name=ACCCN2011>{{cite book|author1=Elliott, Doug |author2=Aitken, Leanne |author3=Chaboyer, Wendy |title=ACCCN's Critical Care Nursing|publisher=Elsevier Australia|location=Chatswood, New South Wales|year=2011|edition=2nd|page=607|isbn=978-0-7295-4068-1|url=https://books.google.com/books?id=8Yg1lsItNdYC&q=redback+spider+ampoule&pg=PA607}}</ref> which is enough to inactivate 5&nbsp;mg of redback spider venom in a test tube.{{sfn|White|2013|p=312}} The antivenom has been safely administered to women in various stages of pregnancy.<ref name=ACCCN2011/> Redback antivenom has been widely used in Australia since 1956, although evidence from [[Scientific control|controlled]] studies for its [[effectiveness]] has been lacking. Recent trials show antivenom has a low response rate little better than placebo, and any effect is less than might be achieved with optimal use of standard analgesics.<ref name=":2" /><ref name=":3" /><ref name=":1" /> Further studies are needed to confirm or refute its effectiveness.<ref name="lancet" /> It appears clinically active against [[arachnidism]] caused by ''Steatoda'' spiders;<ref name="Nicholson2003" /><ref>{{cite journal|last=South|first=Mike|author2=Wirth, Peter|author3=Winkel, Ken D.|title=Redback Spider Antivenom used to Treat Envenomation by a Juvenile ''Steatoda'' Spider|journal=Medical Journal of Australia|date=December 1998|volume=169|issue=11|page=642|url=https://www.mja.com.au/journal/1998/169/11/redback-spider-antivenom-used-treat-envenomation-juvenile-steatoda-spider|pmid=9887917|type=Case report, letter|doi=10.5694/j.1326-5377.1998.tb123445.x|s2cid=33602865|access-date=5 September 2013|archive-date=21 September 2013|archive-url=https://web.archive.org/web/20130921060117/https://www.mja.com.au/journal/1998/169/11/redback-spider-antivenom-used-treat-envenomation-juvenile-steatoda-spider|url-status=live|url-access=subscription}}</ref><ref>{{cite journal|last=Graudins|first=Andis|author2=Gunja, Narendra |author3=Broady, Kevin W. |author4= Nicholson, Graham M. |title=Clinical and ''in vitro'' Evidence for the Efficacy of Australian Red-back Spider (''Latrodectus hasselti'') Antivenom in the Treatment of Envenomation by a Cupboard Spider (''Steatoda grossa'')|journal=Toxicon|date=June 2002|volume=40|issue=6|pages=767–75|doi=10.1016/S0041-0101(01)00280-X|pmid=12175614|bibcode=2002Txcn...40..767G |type=Case report}}</ref><ref>{{cite journal|last1=Atakuziev|first1=Bakhadir U.|last2=Wright|first2=Christine E.|last3=Graudins|first3=Andis|last4=Nicholson|first4=Graham M.|last5=Winkel|first5=Kenneth D.|title=Efficacy of Australian red-back spider (Latrodectus hasselti) antivenom in the treatment of clinical envenomation by the cupboard spider Steatoda capensis (Theridiidae)|journal=Toxicon|volume=86|pages=68–78|doi=10.1016/j.toxicon.2014.04.011|pmid=24853919|year=2014|bibcode=2014Txcn...86...68A }}</ref> however, as these cases are often mild and the evidence of its effectiveness is limited, this treatment is not recommended.<ref name="lancet" /> Similarly, the antivenom has been reported as effective with bites of ''L. katipo'', and ''L. tredecimguttatus''.<ref name="Nicholson2003">{{cite journal|last=Nicholson|first=Graham M.|author2=Graudins, Andis|title=Antivenoms for the Treatment of Spider Envenomation|journal=Toxin Reviews|date=1 January 2003|volume=22|issue=1|pages=35–59|doi=10.1081/TXR-120019019|hdl=10453/4596|s2cid=84894614|hdl-access=free}}</ref> Animal studies also support its use against envenomation from other widow spiders, having successfully been tested against venom from ''L. mactans'', ''[[Latrodectus hesperus|L. hesperus]]'', and ''[[Latrodectus tredecimguttatus|L. tredecimguttatus]]'' ([[Synonym (taxonomy)|synonym]] ''L.&nbsp;lugubris'').<ref name="Nicholson2003" /><ref>{{cite journal|last=Graudins|first=Andis|author2=Padula, Matthew |author3=Broady, Kevin |author4= Nicholson, Graham M. |title=Red-back Spider (''Latrodectus hasselti'') Antivenom Prevents the Toxicity of Widow Spider Venoms|journal=Annals of Emergency Medicine|date=February 2001|volume=37|issue=2|pages=154–60|doi=10.1067/mem.2001.113033|pmid=11174232}}</ref><ref>{{cite journal|last1=Daly |first1=Frank |last2=Hill |first2=Robert E. |last3=Bogdan |first3=Gregory M. |last4=Dart |first4=Richard C.|title=Neutralization of ''Latrodectus mactans'' and ''L. hesperus'' Venom by Redback Spider (''L. hasseltii'') antivenom|journal=Clinical Toxicology|date=1 January 2001|volume=39|issue=2|pages=119–23|doi=10.1081/CLT-100103826|pmid=11407496|last5=Dart|first5=Richard C.|s2cid=22286370 |type=Comparative study}}</ref>

===Signs and symptoms===
{{Main|Latrodectism}}
Envenomation from a redback spider bite produces a syndrome known as [[latrodectism]]. A small but significant percentage of people bitten develop significant pain or systemic symptoms.<ref name=isbister2006/> The diagnosis is made from the clinical condition, often based on the victim being aware of a bite and ideally with identification of the spider. Laboratory tests are rarely needed and there is no specific test for the venom or latrodectism.<ref name="lancet"/>

The redback's small size means that swelling or puncture marks at the bite site are uncommon. The bite may be painful from the start, but more often only feels like a pinprick or mild burning sensation.<ref name=Ibister2004/> Within an hour, a more severe local pain may develop with local sweating and sometimes [[piloerection]] (goosebumps)—these three symptoms together are a classic presentation of redback spider envenomation.{{sfn|White|2013|p=183}} Pain, swelling and redness can spread proximally up a limb or away from the bite site<ref name="Slaughter">{{cite journal|author1=Slaughter, R. J. |author2=Beasley, D. M. |author3=Lambie, B. S. |author4=Schep, L. J. |title=New Zealand's venomous creatures |journal=[[The New Zealand Medical Journal]] |volume=122 |issue=1290 |pages=83–97 |year=2009 |pmid=19319171 |url=http://www.nzma.org.nz/journal/122-1290/3494/ |url-status=dead |archive-url=https://web.archive.org/web/20110417090807/http://www.nzma.org.nz/journal/122-1290/3494/ |archive-date=17 April 2011 }}</ref><ref name=Ibister2004>{{cite journal|last=Isbister|first=Geoffrey K.|author2=White, Julian |title=Clinical Consequences of Spider Bites: Recent Advances in our Understanding|journal=Toxicon|date=April 2004|volume=43|issue=5|pages=477–92|doi=10.1016/j.toxicon.2004.02.002|pmid=15066408|bibcode=2004Txcn...43..477I |type=Review}}</ref><ref name="lancet"/><!--cites 2 sentences-->
and regional lymph nodes may become painful.<ref name="jelinek1997"/> Some subjects with delayed symptoms may present with a characteristic sweating and pain in the lower limbs,{{sfn|White|2013|p=183}} generally below the knees,<ref name="lancet"/> or a burning sensation in the soles of the feet. This may eventuate even if the person was bitten somewhere else on their body.{{sfn|White|2013|p=183}}<!-- cites previous 1.5 sentences -->

Around one in three subjects develops systemic symptoms;<ref name="lancet"/> after a number of hours, or rarely, delayed for more than 24 hours.<ref name="sutherland"/><ref name=jelinek1989>{{cite journal |author1=Jelinek, G. A. |author2=Banham, N. D. |author3=Dunjey, S. J. |title=Red-back Spider-bites at Fremantle Hospital, 1982–1987|journal=Medical Journal of Australia |volume=150 |issue=12 |pages=693–95 |year=1989 |pmid= 2733615|type=Case report|doi=10.5694/j.1326-5377.1989.tb136762.x |s2cid=204110952 }}</ref> Symptoms typically include nausea, vomiting, abdominal or chest pain, agitation, headache, generalised sweating and [[hypertension]].<ref name="lancet"/>{{sfn|White|2013|p=183}} Other non-specific systemic effects such as malaise and lethargy are also common. Rarely, other effects are reported such as neurological manifestations, fever and priapism (uncontrolled erection of the penis).<ref name=":2" /> Severe pain usually persists for over 24 hours after being bitten. Symptoms of envenomation may linger for weeks or even months.<ref name=Nimorakiotakis/> Rare complications include localised skin infection, seizure, coma, [[pulmonary oedema]], or [[respiratory failure]].<ref name="sutherland"/> Children, the elderly, or those with serious medical conditions are at much higher risk of severe effects resulting from a bite.<ref name="White"/> Infants have died within hours of a bite, but adult fatalities have taken up to 30 days.<ref name=MorningBulletin1954>{{cite news |url=http://nla.gov.au/nla.news-article57311162 |title=Nature Notes Red-backs and Black Widow |newspaper=[[The Morning Bulletin]] |location=Rockhampton, Queensland |date=2 March 1954 |page=6 |publisher=National Library of Australia |access-date=4 September 2013 |archive-date=19 October 2021 |archive-url=https://web.archive.org/web/20211019063040/https://trove.nla.gov.au/newspaper/article/57311162 |url-status=live }}</ref>

Children and infants may be unable to report being bitten, making it difficult to associate their symptoms with a spider bite.<ref name=isbister2006>{{cite journal|last=Isbister |first=Geoffrey K |year=2006 |title=Spider bite: a current approach to management |journal=Australian Prescriber |volume=29 |issue=6 |pages=156–58 |doi=10.18773/austprescr.2006.095 |doi-access=free }}</ref> Symptoms seen in infants include inconsolable crying, refusing to feed and a general [[erythema]]tous rash.{{sfn|White|2013|p=225}}{{efn|Published studies specifically looking at effects in children have been retrospective only and too limited to draw conclusive results.<ref name=Ibister2004/> A ten-year retrospective study of children bitten and admitted to hospital in Perth found that the clinical features resemble those of adult cases, and 21% required antivenom—a rate similar to adult use,<ref>{{cite journal|author1=Mead, H.J. |author2=Jelinek, G.A. |year=1993|title=Red-back Spider Bites to Perth Children, 1979–1988|journal=Journal of Paediatrics and Child Health|volume=29|issue=4|pages=305–08 |doi=10.1111/j.1440-1754.1993.tb00518.x|pmid=8373679 |s2cid=25640556 }}</ref> while a ten-year retrospective study from Alice Springs Hospital found that 83% required antivenom therapy, with irritability, hypertension and sweating as the most common clinical symptoms.<ref name=Trethewy2003>{{cite journal|author1=Trethewy, Christopher E. |author2=Bolisetty, Srinivas |author3=Wheaton, Gavin |year=2003|title=Red-back Spider Envenomation in Children in Central Australia|journal=Emergency Medicine|volume=15|issue=2|pages=170–75|doi=10.1046/j.1442-2026.2003.00435.x|pmid=12675627}}</ref>}} Muscle aches and pains, and neck spasm are often seen in children over four years of age.<ref name=Nimorakiotakis/>

Unlike those of some other spiders, redback bites do not [[necrosis|necrose]].<ref>{{cite journal|last=Young|first=Anna R.|author2=Pincus, Steven J. |title=Comparison of Enzymatic Activity from Three Species of Necrotising Arachnids in Australia: ''Loxosceles rufescens'', ''Badumna insignis'' and ''Lampona cylindrata''|journal=Toxicon|date=February–March 2001|volume=39|issue=2–3|pages=391–400|doi=10.1016/S0041-0101(00)00145-8|pmid=10978759|bibcode=2001Txcn...39..391Y |type=Comparative study}}</ref> <!-- Even envenomated bites do not cause miscarriage of pregnancies, and foetuses are typically unaffected.<ref>{{cite journal|last=Vetter|first=Richard S.|author2=Visscher, P. Kirk |title=Bites and Stings of Medically Important Venomous Arthropods|journal=International Journal of Dermatology|date=July 1998|volume=37|issue=7|pages=481–96|doi=10.1046/j.1365-4362.1998.00455.x|pmid=9679688}}</ref> --> Latrodectism has been misdiagnosed as various medical conditions including [[acute hepatitis]], [[sepsis]], [[testicular torsion]] or an [[acute abdomen]].<ref name=Nimorakiotakis/>

===Treatment===
Treatment is based on the severity of the envenomation. The majority of cases do not require medical care, and patients with localised pain, swelling and redness usually require only local application of ice and simple oral [[analgesia]] such as [[paracetamol]]. Pressure immobilisation of the wound site is not recommended. Keeping the victim still and calm is beneficial.<ref name="Slaughter"/><ref>{{cite web|url=http://www.ambulance.nsw.gov.au/Media/docs/funnel_web_and_redback_spider_bites-5d64cbaa-fbb8-439f-b281-0d0c4d380cbb-0.pdf|title=Funnel Web and Redback Spider Bites: First Aid Advice|author=New South Wales Ambulance Service|year=2008|work=Standard Operating Policy|publisher=State Government of New South Wales|access-date=13 October 2013|archive-date=6 March 2014|archive-url=https://web.archive.org/web/20140306160437/http://www.ambulance.nsw.gov.au/Media/docs/funnel_web_and_redback_spider_bites-5d64cbaa-fbb8-439f-b281-0d0c4d380cbb-0.pdf|url-status=live}}</ref>

Hospital assessment is recommended if simple pain relief does not resolve local pain, or systemic symptoms occur.{{sfn|White|2013|p=198}}<ref name="Murray">{{cite book | last = Murray | first = L. | author2 = Daly, F.| author3 = Little, M.| author4 = Cadogan, M.| title = Toxicology Handbook| publisher = Churchill Livingstone| location = Sydney | year = 2011 | pages = 470–79| isbn = 978-0-7295-3939-5}}</ref> [[Opioid]] analgesics may be necessary to relieve pain.<ref name="lancet"/> Antivenom has been historically given for adults suffering severe local pain or systemic symptoms consistent with latrodectism, which include pain and swelling spreading proximally from site, distressing local or systemic pain, chest pain, abdominal pain, or excessive sweating ([[diaphoresis]]).{{sfn|White|2013|pp=203–04}} A significant proportion of bites will not result in envenomation or any symptoms developing; around 2–20% of bite victims have been treated with antivenom.{{efn|The exact fraction of bites that require antivenom is difficult to quantify, because many bites are unreported. Figures from the manufacturer show that 344 cases required antivenom treatment in 1995,<ref name=White1998/> and in 2011 the figure was around 200.<ref name=Booth2008/> Estimates for the total number of bites range from 2,000<ref name=Nicholson2003/> to 10,000.<ref name=White1998/> These estimates correspond to a broad range of about 2–17%, and reports have generally expressed this as "around" or "under" 20%.<ref name=Nicholson2003/><ref name=White1998/> Two studies of redback victims who attended hospitals found that 6/23 (26%)<ref name="isbister"/> and 32/150 (21%)<ref name="jelinek1989"/> received antivenom.}}<ref name=White1998>{{cite journal |author=White, J. |title=Envenoming and Antivenom use in Australia |journal=Toxicon |volume=36 |issue=11 |pages=1483–92 |year=1998 |pmid=9792162 |doi=10.1016/S0041-0101(98)00138-X|bibcode=1998Txcn...36.1483W }}</ref> In an Australian study of 750 emergency hospital admissions for spider bites where the spider was definitively identified, 56 were from redbacks. Of these, 37 had significant pain lasting over 24 hours. Only six were treated with the antivenom.<ref name="bite study">{{Cite journal | last1 = Isbister | first1 = G. K. | last2 = Gray | first2 = M. R. | title = A Prospective Study of 750 Definite Spider Bites, with Expert Spider Identification | doi = 10.1093/qjmed/95.11.723 | journal = QJM | volume = 95 | issue = 11 | pages = 723–31 | year = 2002 | pmid =  12391384| doi-access = free }}</ref>

The antivenom manufacturer's product information recommends one vial, although more has been used.{{sfn|White|2013|p=312}} Past guidelines indicated two vials, with a further two vials recommended if symptoms did not resolve within two hours, however recent guidelines state "antivenom is sometimes given if there is a history, symptoms and signs consistent with systemic envenoming, and severe pain unresponsive to oral analgesics ... however recent trials show antivenom has a low response rate little better than placebo, and any effect is less than might be achieved with optimal use of standard analgesics."{{sfn|White|2013|pp=203–04}}<ref name=":2" /> The antivenom can be given by injection [[Intramuscular injection|intramuscularly]] (IM) or [[Intravenous therapy|intravenously]] (IV). The manufacturer recommends IM use, with IV administration reserved for life-threatening cases.<ref name="proinfo">{{cite web|url=http://www.csl.com.au/s1/cs/auhq/1196562765747/Web_Product_C/1196562644318/ProductDetail.htm|title=Redback Antivenom Product Information|year=2009|publisher=CSL Ltd|location=Melbourne, Australia|access-date=10 September 2013|archive-date=21 September 2013|archive-url=https://web.archive.org/web/20130921055927/http://www.csl.com.au/s1/cs/auhq/1196562765747/Web_Product_C/1196562644318/ProductDetail.htm|url-status=live}}</ref> In January 2008 toxicologist Geoffrey Isbister suggested IM antivenom was not as effective as IV antivenom,<ref name="isbister"/><ref>{{cite journal |doi=10.1046/j.1442-2026.2002.00356.x |author=Isbister, Geoff |title=Failure of Intramuscular Antivenom in Redback Spider Envenoming |journal=Emergency Medicine Australasia |volume=14 |issue=4 |pages=436–39 |year=2002 |pmid=12534488}}</ref> after proposing that IM antivenom took longer to reach the [[Serum (blood)|blood serum]].<ref name="serum study">{{Cite journal | last1 = Isbister | first1 = G. K. | last2 = O'Leary | first2 = M. | last3 = Miller | first3 = M. | last4 = Brown | first4 = S. G. A. | last5 = Ramasamy | first5 = S. | last6 = James | first6 = R. | last7 = Schneider | first7 = J. S. | doi = 10.1111/j.1365-2125.2007.03004.x | title = A comparison of serum antivenom concentrations after intravenous and intramuscular administration of redback (widow) spider antivenom | journal = British Journal of Clinical Pharmacology | volume = 65 | issue = 1 | pages = 139–43 | year = 2008 | pmid =  18171334| pmc =2291270 }}</ref> Isbister subsequently found the difference between IV and IM routes of administration was, at best, small and did not justify routinely choosing one route over the other.<ref>{{cite journal|vauthors=Isbister GK, Brown SG, Miller M, Tankel A, Macdonald E, Stokes B, Ellis R, Nagree Y, Wilkes GJ, James R, Short A|title=A randomised controlled trial of intramuscular vs. intravenous antivenom for latrodectism—the RAVE study|journal=QJM|year=2008|volume=101|issue=7|pages=557–65|doi=10.1093/qjmed/hcn048|pmid=18400776|doi-access=free}}</ref>

These concerns led two handbooks to recommend IV in preference to IM administration in Australian practice.{{sfn|White|2013|p=205}}<ref name="Murray"/>{{efn|A 2006 questionnaire found that of 218 Emergency physicians, 34 used the antivenom IM exclusively, 36 used IM then IV, 63 IV exclusively and 80 had no preference—that is, there was no consensus for preferred route.<ref>{{cite journal|author1=Brown, Simon A. |author2=Isbister, Geoffrey K. |year=2007|title=Route of administration of redback spider bite antivenom: Determining clinician beliefs to facilitate Bayesian analysis of a clinical trial|journal=Emergency Medicine Australasia |volume=19|issue=5|pages=458–63 |doi=10.1111/j.1742-6723.2007.01014.x|pmid=17919219|s2cid=310139 }}</ref>}} Despite a long history of usage and anecdotal evidence of effectiveness, there is a lack of data from controlled studies confirming the antivenom's benefits.<ref name="lancet"/> In 2014 Isbister and others conducted a randomized controlled trial of intravenous antivenom versus placebo for Redback envenomation, finding the addition of antivenom did not significantly improve pain or systemic effects, while antivenom resulted in acute hypersensitivity reactions in 3.6 per cent of those receiving it.<ref name=":3">{{cite journal |doi=10.1016/j.annemergmed.2014.06.006 |pmid=24999282 |title=Randomized Controlled Trial of Intravenous Antivenom Versus Placebo for Latrodectism: The Second Redback Antivenom Evaluation (RAVE-II) Study |journal=Annals of Emergency Medicine |volume=64 |issue=6 |pages=620–8.e2 |year=2014 |last1=Isbister |first1=Geoffrey K. |last2=Page |first2=Colin B. |last3=Buckley |first3=Nicholas A. |last4=Fatovich |first4=Daniel M. |last5=Pascu |first5=Ovidiu |last6=MacDonald |first6=Stephen P.J. |last7=Calver |first7=Leonie A. |last8=Brown |first8=Simon G.A. |hdl=2123/14928 |url=https://ses.library.usyd.edu.au/bitstream/2123/14928/1/Isbister_et_al_2014.pdf |hdl-access=free |access-date=24 September 2019 |archive-date=20 July 2018 |archive-url=https://web.archive.org/web/20180720071527/https://ses.library.usyd.edu.au/bitstream/2123/14928/1/Isbister_et_al_2014.pdf |url-status=live }}</ref> The question of abandoning the antivenom on the basis of this and previous studies came up in the Annals of Emergency Medicine in 2015 where White and Weinstein argued that if the recommendations in the 2014 Isbister et al. paper were followed it would lead to abandonment of antivenom as a treatment option, an outcome White and Weinstein considered undesirable. Authors of the 2014 Isbister et al. paper responded in the same issue by suggesting patients for whom antivenom is considered should be fully informed "there is considerable weight of evidence to suggest it is no better than placebo", and in light of a risk of anaphylaxis and serum sickness,  "routine use of the antivenom is therefore not recommended".<ref name=":1">{{cite journal |doi=10.1016/j.annemergmed.2014.08.022 |pmid=25529159 |title=Latrodectism and Effectiveness of Antivenom |journal=Annals of Emergency Medicine |volume=65 |issue=1 |pages=123–24 |year=2015 |last1=White |first1=Julian |last2=Weinstein |first2=Scott A. }}</ref>

Before the introduction of antivenom, [[benzodiazepine]]s and intravenous [[calcium gluconate]] were used to relieve symptoms of pain and distress,<ref name="rauber83" /><ref>{{cite journal|last=Braitberg|first=George|year=2009|title=Spider bites: Assessment and management|url=http://www.racgp.org.au/afp/200911/200911braithberg.pdf|journal=Australian Family Physician|type=Review|volume=38|issue=11|pages=862–67|pmid=19893831|access-date=29 October 2013|archive-date=1 November 2013|archive-url=https://web.archive.org/web/20131101170857/http://www.racgp.org.au/afp/200911/200911braithberg.pdf|url-status=live}}</ref> although calcium is not recommended as its benefit has not been shown in clinical trials.{{sfn|White|2013|p=206}}

Studies support the safety of antivenom, with around a 5% chance of an acute reaction, 1–2% of [[anaphylaxis]] and 10% chance of a delayed reaction due to [[serum sickness]].<ref name="lancet"/> Nevertheless, it is recommended that an injection of [[adrenaline]] be ready and available in case it is needed to treat a severe anaphylactic reaction,<ref name="proinfo"/> and also that the antivenom from the vial be administered diluted in a 100 ml bag of intravenous solution for infusion over 30 minutes.{{sfn|White|2013|p=209}} While it is rare that patients report symptoms of envenomation lasting weeks or months following a bite,<ref name="isbister"/> there are case reports from the 1990s in which antivenom was reported to be effective in the relief of chronic symptoms when administered weeks or months after a bite.<ref>{{cite journal |author1=Banham, N. |author2=Jelinek, G. |author3=Finch, P. |title=Late Treatment with Antivenom in Prolonged Redback Spider Envenomation |journal=Medical Journal of Australia |volume=161 |issue=6 |pages=379–81 |year=1994 |pmid=8090117|type=Case report|doi=10.5694/j.1326-5377.1994.tb127492.x |s2cid=27782875 }}</ref><ref name="Wells">{{cite journal |author1=Wells, C. L. |author2=Spring, W. J. |title=Delayed but Effective Treatment of Red-back Spider Envenomation|journal=Medical Journal of Australia |volume=164 |issue=7 |page=447 |year=1996 |pmid= 8609868|type=Case report, letter|doi=10.5694/j.1326-5377.1996.tb122109.x |s2cid=31114115 }}</ref> However, in the vast majority of cases, it is administered within 24 hours.<ref name="sutherland"/>

===Prognosis===
According to [[Ministry of Health (New South Wales)|NSW Health]], redback spider bites were considered not life-threatening but capable of causing severe pain and systemic symptoms that could continue for hours to days.<ref name=":2" /><ref name=":6">{{Cite web|url=http://www1.health.nsw.gov.au/pds/ActivePDSDocuments/GL2014_005.pdf|title=Snakebite and Spiderbite Clinical Management Guidelines 2013, Third Edition|date=16 March 2014|publisher=Ministry of Health, NSW|access-date=23 October 2017|archive-date=15 December 2017|archive-url=https://web.archive.org/web/20171215111714/http://www1.health.nsw.gov.au/pds/ActivePDSDocuments/GL2014_005.pdf|url-status=live}} [[File:CC-BY icon.svg|50x50px]] Material was copied from this source, which is available under a [[creativecommons:by/4.0/|Creative Commons Attribution 4.0 International License]].</ref> In almost all cases, symptoms resolve within a week.<ref name=isbister2006/> Fatalities are extremely unlikely.{{sfn|White|2013|p=181}} In 2016, the death of a [[hiking|bushwalker]] from a redback spider bite was widely reported. In this case, the death occurred from secondary infection; and the man in question had just recovered from a serious car accident.<ref name="Jayden">{{cite news |url=https://www.northernstar.com.au/news/mullum-man-jayden-burleigh-dies-days-after-redback/2994925/ |title=More than $12k donated to family of man killed by spider |newspaper=[[The Northern Star]] |date=3 April 2016 |access-date=13 August 2018 |archive-date=13 August 2018 |archive-url=https://web.archive.org/web/20180813143325/https://www.northernstar.com.au/news/mullum-man-jayden-burleigh-dies-days-after-redback/2994925/ |url-status=live }}</ref> Apart from that, there have been no deaths due to redback bite since the introduction of [[antivenom]].{{efn|No deaths since 1956 have been formally reported,<ref name="Wiener"/> but a spider expert at the [[CSIRO]] Division of Entomology told a news reporter that he had heard of one other death.<ref name=Warden1989/>}}<ref name="Wiener">{{cite journal |last=Wiener |first=Saul |title=Latrodectism: a Prospective Cohort Study of Bites by Formally Identified Redback Spiders |journal=Medical Journal of Australia |volume=179 |issue=8 |pages=455–56 |year=2003 |pmid=14558881 |url=http://www.mja.com.au/public/issues/179_08_201003/letters201003_fm-8.html |type=Comment, letter |doi=10.5694/j.1326-5377.2003.tb05640.x |s2cid=40170866 |access-date=13 February 2012 |archive-date=1 September 2011 |archive-url=https://web.archive.org/web/20110901081929/http://www.mja.com.au/public/issues/179_08_201003/letters201003_fm-8.html |url-status=live |url-access=subscription }}</ref> Before this, redback spider bites had been implicated in at least 14 deaths in Australia, however these cases cannot be definitively linked to the redback bite as the sole cause.<ref name=Booth2008>{{cite journal |author=Booth, Carol |title=Along Came A Spider |journal=Australian Geographic |date=July–September 2008 |url=http://www.australiangeographic.com.au/journal/along-came-a-spider.htm |access-date=25 March 2010 |archive-url=https://web.archive.org/web/20091006070407/http://www.australiangeographic.com.au/journal/along-came-a-spider.htm |archive-date=6 October 2009 |url-status=dead  }}</ref><ref name=avru>{{cite web|url=http://www.avru.org/compendium/biogs/A000006b.htm |work=The Australian Venom Compendium |author=Alafaci, Annette |title=Redback Spiders |publisher=Australian Venom Research Unit |date= 25 August 2007 |archive-url=https://web.archive.org/web/20150115112010/http://www.avru.org/compendium/biogs/A000006b.htm|archive-date=15 January 2015 |access-date=2 September 2013}}</ref>

==Bites to animals==
Redback spider bites are difficult to diagnose in pets unless witnessed. Dogs appear to have some resistance. They are at serious risk only if bitten many times, and rarely need antivenom. Cats are likely to be more susceptible and require antivenom, which can reverse symptoms very quickly. Guinea pigs, horses and camels are very susceptible. As with humans, the symptoms are predominantly [[autonomic nervous system|autonomic]] in nature alongside pain at the bite site. Dogs may also suffer vomiting and diarrhea, muscle tremors or [[clonic seizure|clonic contractions]], and abdominal wall rigidity, while cats may [[salivate]] excessively, protrude their tongue or be overexcitable.<ref name="AVRU">{{cite web|url=http://www.avru.org/vetpet/vetpet_vetspider.html|title=Spider Bite|last=Brooks|first=R. |date=January 2008|work=Australian Venom Research Unit|publisher=University of Melbourne|archive-url=https://web.archive.org/web/20150217203444/http://www.avru.org/vetpet/vetpet_vetspider.html|archive-date=17 February 2015 |access-date=8 October 2013}}</ref><!-- cites para -->

==Historical treatment of bites==
Most traditional or historical first-aid treatments for redback spider bites are either useless or dangerous.<ref>{{cite web |url=http://www.toxinology.com/fusebox.cfm?fuseaction=main.spiders.display&id=SP00054 |title=Clinical Toxicology Resources |publisher=University of Adelaide |access-date=21 October 2013 |archive-date=21 October 2013 |archive-url=https://web.archive.org/web/20131021193644/http://www.toxinology.com/fusebox.cfm?fuseaction=main.spiders.display&id=SP00054 |url-status=live }}</ref> These include making incisions and promoting bleeding, using [[ligature (medicine)|ligatures]], applying [[alkaline]] solutions,<ref>{{cite news |url=http://nla.gov.au/nla.news-article23033857 |title=Don't Panic, But Treat Red-back Spider with Caution, Say Venom Experts |newspaper=[[The Argus (Melbourne)|The Argus]] |location=Melbourne |date=6 January 1951 |page=3 |publisher=National Library of Australia |access-date=4 September 2013 |archive-date=19 October 2021 |archive-url=https://web.archive.org/web/20211019063040/https://trove.nla.gov.au/newspaper/article/23033857 |url-status=live }}</ref> providing warmth,<ref>{{cite news |url=http://nla.gov.au/nla.news-article67674357 |title=Red-back Spider |newspaper=Advocate |location=Burnie, Tasmania |date=7 September 1929 |page=5 |publisher=National Library of Australia |access-date=4 September 2013 |archive-date=19 October 2021 |archive-url=https://web.archive.org/web/20211019063041/https://trove.nla.gov.au/newspaper/article/67674357 |url-status=live }}</ref> and sucking the venom out.<ref name="autogenerated3"/> In modern first aid, incising, sucking, applying bandages and [[tourniquet]]ing are strongly discouraged.<ref>{{cite web|title=Bites and Stings – First Aid|url=http://www.betterhealth.vic.gov.au/bhcv2/bhcarticles.nsf/pages/Bites_and_stings_first_aid|work=The Better Health Channel|publisher=State Government of Victoria|access-date=21 October 2013|date=September 2011|url-status=dead|archive-url=https://web.archive.org/web/20131021130102/http://www.betterhealth.vic.gov.au/bhcv2/bhcarticles.nsf/pages/Bites_and_stings_first_aid|archive-date=21 October 2013}}</ref> In 1893, the ''[[The Camperdown Chronicle|Camperdown Chronicle]]'' reported that a doctor noticed that a severely ill benumbed victim got much better overnight following treatment using injections of [[strychnine]] and [[cocaine]];<ref name=Camperdown1893/> strychnine had been popular as a snake bite antidote, but it was not effective.<ref>{{cite journal|last=Pinto|first=J. E. B.|author2=Rothlin, R. P.|author3=Dagrosa, E. E.|author4=Barrio, A.|title=On the Bite of the Katipo|journal=Transactions and Proceedings of the Royal Society of New Zealand|year=1900|volume=33|pages=436|url=http://rsnz.natlib.govt.nz/volume/rsnz_33/rsnz_33_00_007890.html|access-date=22 October 2013|archive-date=22 October 2013|archive-url=https://web.archive.org/web/20131022034529/http://rsnz.natlib.govt.nz/volume/rsnz_33/rsnz_33_00_007890.html|url-status=live}}</ref> As of 2011, administration of [[magnesium sulphate]] was reported to have had some benefit though evidence of effectiveness is weak.<ref name="lancet">{{cite journal|author1=Isbister, Geoffrey K. |author2=Fan, Hui Wen |year=2011|title=Spider Bite|journal=The Lancet|volume=378|issue=9808|pages=2039–47|doi=10.1016/S0140-6736(10)62230-1 |pmid= 21762981|s2cid=27408940 |type= Review}}</ref>

==Cultural influence==
[[Indigenous Australians]] in New South Wales mixed the spiders' bodies with the venom of snakes and pine tree gum to form a broth used to coat spear tips.<ref>{{cite news |url=http://nla.gov.au/nla.news-article64034545 |title=The Aborigines of New South Wales{{snd}}their Habits, Laws, and Customs. |newspaper=[[Illustrated Sydney News]] |location=NSW |date=14 April 1883 |page=14 |publisher=National Library of Australia |access-date=1 September 2013 |archive-date=19 October 2021 |archive-url=https://web.archive.org/web/20211019063041/https://trove.nla.gov.au/newspaper/article/64034545 |url-status=live }}</ref> [[Slim Newton]] drew popular attention to redbacks with his song "[[The Redback on the Toilet Seat]]", which won the [[Golden Guitar]] at the first [[Country Music Awards of Australia]] in 1973.<ref>{{cite web|title=Slim Newton|publisher=The Country Music Store|date=2 January 1998|url=http://www.countrymusic.com.au/bellbird/Biographies/Slim%20Newton.htm|access-date=24 September 2013|archive-date=27 September 2013|archive-url=https://web.archive.org/web/20130927162727/http://www.countrymusic.com.au/bellbird/Biographies/Slim%20Newton.htm|url-status=live}}</ref><ref>{{cite web|title=Bellbird Music|publisher=The Country Music Store|date=6 July 2009|url=http://www.countrymusic.com.au/bellbird/|access-date=24 September 2013|archive-url=https://web.archive.org/web/20130927162725/http://www.countrymusic.com.au/bellbird/|archive-date=27 September 2013|url-status=dead}}</ref> Newton recalled an occasion when a friend used his outside toilet where the light globe had blown and reported he was lucky there was not a redback spider on the toilet seat. The phrase inspired him to write the song.<ref name="Musgrove">{{cite news | url = http://nla.gov.au/nla.news-article46445461 | title = Slim Newton and His Spider | last = Musgrove | first = Nan | newspaper = [[The Australian Women's Weekly]] | date = 2 August 1972 | access-date = 3 November 2013 | page = 7 | publisher = National Library of Australia | archive-date = 19 October 2021 | archive-url = https://web.archive.org/web/20211019063041/https://trove.nla.gov.au/newspaper/article/46445461 | url-status = live }}</ref> <!--The song is often erroneously ascribed to [[Slim Dusty]].[http://www.onlysydney.com.au/slim-newton-redback-on-the-toilet-seat]--> A sculpture of an impossibly large redback, one of [[Australia's big things]], was built in 1996 at [[Eight Mile Plains, Queensland|Eight Mile Plains]], Queensland.<ref>{{cite book | last = Clark | first = David | year = 2004 | title = Big Things: Australia's Amazing Roadside Attractions | publisher = Penguin Books | isbn = 0-14-300200-7 |page=62}}</ref> [[The Angels (Australian band)|The Angels]] 1991 album ''[[Red Back Fever]]'' takes its name from the spider.<ref>{{cite book|title=The Dictionary of Performing Arts in Australia: Opera, Music, Dance|year=1996|publisher=Allen & Unwin|isbn=978-1-86373-898-9|url=https://books.google.com/books?id=ELACebeQEgcC&q=red%20back%20fever%20angels&pg=PA9|author1=Atkinson, Ann|author2=Knight, Linsay|author3=McPhee, Margaret|page=9|access-date=1 November 2020|archive-date=19 October 2021|archive-url=https://web.archive.org/web/20211019063040/https://books.google.com/books?id=ELACebeQEgcC&q=red+back+fever+angels&pg=PA9|url-status=live}}</ref><ref>{{cite magazine|last=Tulich|first=Katherine|title=Oz invaders: who they are, how they sound. (Australian musical acts) (Spotlight on Australia)|url=http://trove.nla.gov.au/work/51165253?c=article&versionId=64102657|magazine=Billboard|date=9 May 1992|volume=104|issue=19|page=A6|issn=0006-2510|access-date=6 November 2013|archive-date=11 November 2013|archive-url=https://web.archive.org/web/20131111090818/http://trove.nla.gov.au/work/51165253?c=article&versionId=64102657|url-status=live}}</ref> [[Matilda Bay Brewing Company]] produces a wheat beer called Redback,<ref>{{cite news|url=https://news.google.com/newspapers?id=EX5VAAAAIBAJ&dq=matilda-bay-brewing&pg=3117%2C632338|title=Hoppy Flavors Fit Company for Food|newspaper=The Age|date=23 August 1988|page=31|access-date=27 August 2020|archive-date=19 October 2021|archive-url=https://web.archive.org/web/20211019063040/https://news.google.com/newspapers?id=EX5VAAAAIBAJ&dq=matilda-bay-brewing&pg=3117%2C632338|url-status=live}}</ref> with the distinctive red stripe as the logo.<ref>{{cite web |url=http://www.brewsnews.com.au/2012/10/would-the-real-first-matilda-bay-beer-please-stand-up/ |title=Would the Real First Matilda Bay Beer Please Stand Up? |publisher=Australian Brews News |website=Brewsnews.com.au |date=2 October 2012 |access-date=2 September 2013 |archive-date=28 September 2013 |archive-url=https://web.archive.org/web/20130928164154/http://www.brewsnews.com.au/2012/10/would-the-real-first-matilda-bay-beer-please-stand-up/ |url-status=live }}</ref> The redback formerly appeared in the name and emblem of the [[South Australia cricket team]].<ref>{{cite news |url=http://www.adelaidenow.com.au/news/south-australia/saca-goes-in-to-bat-on-logo/story-e6frea83-1111116848650 |title=SACA goes in to Bat on Logo |work=The Advertiser |date=6 July 2008 |last=Lower |first=Gavin |access-date=4 September 2013 |archive-date=3 October 2013 |archive-url=https://web.archive.org/web/20131003002050/http://www.adelaidenow.com.au/news/south-australia/saca-goes-in-to-bat-on-logo/story-e6frea83-1111116848650 |url-status=live }}</ref><ref>{{cite web |url=http://www.redbacks.com.au/ |title=Home |work=West End Redbacks |publisher=self-published |date=29 August 2013 |access-date=2 September 2013 |archive-date=30 December 2012 |archive-url=https://archive.today/20121230185818/http://www.redbacks.com.au/ |url-status=live }}</ref> The [[Airborne Redback]], an Australian [[ultralight trike]], was also named after the spider.<ref name="WDLA04">Bertrand, Noel; Coulon, Rene (2003). ''World Directory of Leisure Aviation 2003–04''. Lancaster OK: Pagefast Ltd: 92. {{ISSN|1368-485X}}</ref> [[Redback Boots]] is an Australian workboot manufacturing company,<ref>{{cite news|last=Booth|first=Meredith|title=Boots jobs 'safe' in Adelaide after plant closes|url=http://www.news.com.au/national/boots-jobs-safe-in-adelaide-after-plant-closes/story-e6frfkx9-1111112851173|access-date=6 November 2013|newspaper=News.com.au|date=18 January 2007|url-status=dead|archive-url=https://web.archive.org/web/20131208065147/http://www.news.com.au/national/boots-jobs-safe-in-adelaide-after-plant-closes/story-e6frfkx9-1111112851173|archive-date=8 December 2013}}</ref> which uses the spider in its name and logo.<ref>{{cite web|title=Redback 100% Australian Boot Company|url=http://www.redback.net.au/|publisher=self-published|work=Redback Boots|access-date=6 November 2013|archive-date=4 November 2013|archive-url=https://web.archive.org/web/20131104124714/http://www.redback.net.au/|url-status=live}}</ref> In 2006 a redback spider postage stamp was designed as part of a "Dangerous Australians" stamp series, but was withheld from general circulation by [[Australia Post]] due to concerns that the realistic depiction would scare people opening their [[letter box]]es.<ref>{{cite news|title=Spider Stamped On|date=6 July 2006|work=Sydney Morning Herald|url=http://www.smh.com.au/news/stay-in-touch/the-daddy-of-all-pirates/2006/07/05/1151779012831.html?page=fullpage#contentSwap2|access-date=11 November 2013|archive-date=30 December 2013|archive-url=https://web.archive.org/web/20131230192408/http://www.smh.com.au/news/stay-in-touch/the-daddy-of-all-pirates/2006/07/05/1151779012831.html?page=fullpage#contentSwap2|url-status=live}}</ref> In 2012 an episode of the children's TV show ''[[Peppa Pig]]'' in which the title character picks up and plays with a spider was banned from Australian television due to fears that it would encourage children to pick up and play with redback spiders.<ref>{{Cite news |last=Zhou |first=Naaman |date=2017-09-05 |title=Peppa Pig 'spiders can't hurt you' episode pulled off air in Australia – again |language=en-GB |work=The Guardian |url=https://www.theguardian.com/tv-and-radio/2017/sep/05/peppa-pig-spiders-cant-hurt-you-episode-pulled-off-air-in-australia-again |access-date=2023-10-18 |issn=0261-3077}}</ref>

==See also==
* [[List of common spiders of Australia]]
* [[Spiders of Australia]]

==Notes==
{{Notelist}}{{Clear}}

==References==
{{Reflist}}

===Cited texts===
* {{cite book|last=Brunet|first=Bert|title=Spiderwatch: A Guide to Australian Spiders|publisher=Reed|year=1997  |isbn=0-7301-0486-9}}
* {{cite book|last=McKeown|first=Keith C. |title=Australian Spiders |publisher=Sirius Books: Angus and Robertson |year=1963 |orig-year=1936  }}
* {{cite book|last1=Sutherland|first1=Struan K.|last2=Tibballs |first2=James |title=Australian Animal Toxins|edition=2nd |year=2001|orig-year=1983 |publisher=Oxford University Press |location=South Melbourne, Victoria  |isbn=0-19-550643-X}}
* {{cite book | last = White | first = Julian | title = A Clinician's Guide to Australian Venomous Bites and Stings: Incorporating the Updated Antivenom Handbook | publisher = CSL Ltd| location = Melbourne, Victoria | year = 2013 | isbn = 978-0-646-57998-6}}
* {{Cite book|title=A Field Guide to Spiders of Australia|last1=Whyte|first1=Robert|last2=Anderson|first2=Greg|publisher=CSIRO Publishing|isbn=978-0-643-10707-6|location=Clayton, South VIC|lccn=2017302819|oclc=971943480|year=2017}}

==External links==
{{Commons|Latrodectus hasselti|''Latrodectus hasselti''}}
{{Wikispecies|Latrodectus hasselti|''Latrodectus hasselti''}}
* [https://bie.ala.org.au/species/https://biodiversity.org.au/afd/taxa/c7d8dbc8-dcde-4182-85ba-907182f95ea9 ''Latrodectus hasselti''] in the [[Atlas of Living Australia]]

{{Taxonbar|from=Q82544}}
{{Authority control}}

[[Category:Endemic fauna of Australia]]
[[Category:Latrodectus]]
[[Category:Spiders of Australia]]