Editing Redback spider (section)

==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"/>