Editing Redback spider (section)

===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"/>