Editing Latrodectus

{{Short description|Genus of spiders}}
{{About|the genus of spider|other uses|Black Widow (disambiguation){{!}}Black widow}}
{{Automatic taxobox
| image = Latrodectus hesperus Berkeley, California.jpg
| image_caption = Female ''[[Latrodectus hesperus]]'', or western black widow
| taxon = Latrodectus
| authority = [[Charles Athanase Walckenaer|Walckenaer]], 1805<ref name=WSC_g3502/>
| type_species = ''[[Latrodectus tredecimguttatus|L. tredecimguttatus]]''
| type_species_authority = ([[Pietro Rossi (scientist)|Rossi]], 1790)
| subdivision_ranks = Species
| subdivision = 34, [[#Species|see text]]
| synonyms = *''Chacoca'' <small>Badcock, 1932</small><ref name="levi 1959" />
| synonyms_ref = <ref name=WSC_g3502/>
}}
'''''Latrodectus''''' is a broadly distributed [[genus]] of [[spider]]s with several species that are commonly known as the '''true widows'''. This group is composed of those often loosely called '''black widow spiders''', '''brown widow spiders''', and similar spiders.<ref name=":0">{{cite journal |last= Ushkaryov |first=Y. A. |year=2004 |title=The multiple actions of black widow spider toxins and their selective use in neurosecretion studies |journal=Toxicon |volume= 213 |issue=5 |pages=527–542 |doi=10.1016/j.toxicon.2004.02.008|pmid=15066411|bibcode=2004Txcn...43..527U }}</ref><ref name=":1">{{Cite journal |last= Sari |first=I. |year=2008 |title=Myocarditis after black widow spider envenomation. |journal=The American Journal of Emergency Medicine |volume=630 |issue=5 |pages=e1–3 |doi=10.1016/j.ajem.2007.09.012|pmid=18534303}}</ref><ref name=":2">{{cite book |chapter= Impact of Non-native Animals and Plants on Human Health |last=Nentwig |first=N. |publisher=Springer |year=2017 |pages=277–293 |doi=10.1007/978-3-319-45121-3_18|title = Impact of Biological Invasions on Ecosystem Services |isbn=978-3-319-45119-0}}</ref><ref name=":4">{{cite journal |last= Müller |first= G. J. |year=1993 |title=Black and brown widow spider bites in South Africa |url=https://www.ajol.info/index.php/samj/article/view/157941 |journal=South African Medical Journal |volume=83}}</ref> However, the diversity of species is much greater. A member of the family [[Theridiidae]], this genus contains 34 [[species]],<ref name=WSC_sl3502/> which include several North American "black widows" (southern Black Widow ''[[Latrodectus mactans]]'', western black widow ''[[Latrodectus hesperus]]'', and northern black widow ''[[Latrodectus variolus]]''). Besides these, North America also has the red widow ''[[Latrodectus bishopi]]'' and the brown widow ''[[Latrodectus geometricus]]'', which, in addition to North America, has a much wider geographic distribution. Elsewhere, others include the European black widow (''[[Latrodectus tredecimguttatus]]''), the Australian [[redback spider]] (''Latrodectus hasseltii'') and the closely related New Zealand [[katipō]] (''Latrodectus katipo''), several different species in Southern Africa that can be called [[button spider]]s, and the South American black-widow spiders (''[[Latrodectus corallinus]]'' and ''[[Latrodectus curacaviensis]]''). Species vary widely in size. In most cases, the females are dark-coloured and can be readily identified by reddish markings on the central underside (ventral) abdomen, which are often [[hourglass]]-shaped.

These small spiders have an unusually potent venom containing the [[neurotoxin]] [[latrotoxin]], which causes the condition [[latrodectism]], both named after the genus. Female widow spiders have unusually large venom glands, and their [[spider bite|bite]] can be particularly harmful to large vertebrates, including humans. However, despite their notoriety, ''Latrodectus'' bites rarely cause death or produce serious complications.{{citation needed|date=May 2024}} Only the bites of the females are dangerous to humans.

==Description==
[[File:Latrodectus eye group.svg|thumb|The eye arrangement of spiders in the genus ''Latrodectus'']]
Female widow spiders are typically dark brown or a shiny black in colour when they are full grown, usually exhibiting a red or orange hourglass on the [[Anatomical terms of location|ventral]] surface (underside) of the abdomen; some may have a pair of red spots or have no marking at all. The male widow spiders often exhibit various red or red and white markings on the [[Anatomical terms of location|dorsal]] surface (upper side) of the abdomen, ranging from a single stripe to bars or spots, and juveniles are often similar to the male pattern. Females of a few species are paler brown and some have no bright markings. The bodies of black widow spiders range from {{cvt|3-10|mm|in}} in size; some females can measure {{cvt|13|mm|in}} in their body length (not including legs).<ref>{{cite web|title=Black Widow Spiders|url=http://www.orkin.com/other/spiders/black-widows/|website=Orkin Pest Control|access-date=19 June 2017}}</ref>  Including legs, female adult black widows generally measure {{cvt|1|-|1.5|in|mm|order=flip}}.<ref>{{Cite web |date=2014-03-01 |title=Black Widow |url=https://kids.nationalgeographic.com/animals/invertebrates/facts/black-widow |access-date=2024-04-01 |website=Animals |language=en}}</ref><ref>{{Cite web |title=Southern Black Widow Spider |url=https://extension.psu.edu/southern-black-widow-spider |access-date=2024-04-01 |website=extension.psu.edu |language=en}}</ref>

==Behaviour==
[[File:black-widow-red-spots-yellow-legs.jpg|thumb|right|Juvenile southern black widow (''[[Latrodectus mactans]]'')]]
The prevalence of [[sexual cannibalism]], a behaviour in which the female eats the male after mating, has inspired the [[common name]] "widow spiders".<ref>{{cite journal |last1=Breene |first1=R. G. |last2=Sweet |first2=M. H. |year=1985 |title=Evidence of insemination of multiple females by the male Black Widow Spider, ''Latrodectus mactans'' (Araneae, Theridiidae) |journal=The Journal of Arachnology |volume=13 |issue=3 |pages=331–335 |url=http://www.americanarachnology.org/JoA_free/JoA_v13_n3/JoA_v13_p331.pdf}}</ref> This behaviour may promote the survival odds of the [[offspring]];<ref>{{cite journal |last1=Welke |first1=Klaas W. |last2=Schneider |first2=Jutta M. |title=Sexual cannibalism benefits offspring survival |journal=Animal Behaviour |date=January 2012 |volume=83 |issue=1 |pages=201–207 |doi=10.1016/j.anbehav.2011.10.027 |s2cid=53149581}}
*{{cite news |author=Jennifer Welsh |date=December 23, 2011 |title=Male Spiders Let Mates Eat Them for Kids' Sake |work=LiveScience |url=http://www.livescience.com/17616-spider-sexual-cannibalism-offspring.html}}</ref> however, females of some species only rarely show this behaviour, and much of the documented evidence for sexual cannibalism has been observed in laboratory cages where the males could not escape. Male black widow spiders tend to select their mates by determining if the female has eaten already to avoid being eaten themselves. They are able to tell if the female has fed by sensing chemicals in the web.<ref>{{cite journal|last1=Johnson|first1=J. Chadwick|last2=Trubl|first2=Patricia|last3=Blackmore|first3=Valerie|last4=Miles|first4=Lindsay|title=Male black widows court well-fed females more than starved females: silken cues indicate sexual cannibalism risk|journal=Animal Behaviour|date=August 2011|volume=82|issue=2|pages=383–390|doi=10.1016/j.anbehav.2011.05.018|s2cid=53167419}}</ref><ref>{{cite journal|last1=Baruffaldi|first1=Luciana|last2=Andrade|first2=Maydianne C.B.|title=Contact pheromones mediate male preference in black-widow spiders: avoidance of hungry sexual cannibals?|journal=Animal Behaviour|date=April 2015|volume=102|pages=25–32|doi=10.1016/j.anbehav.2015.01.007|s2cid=53186634}}</ref> ''[[Latrodectus hesperus]]'' is referred to as an "opportunistic cannibal" because in dire situations it will resort to cannibalism.<ref>{{cite journal|last=Salomon|first=Maxence|date=April 2011|title=The natural diet of a polyphagous predator, ''Latrodectus hesperus'' (Araneae: Theridiidae), over one year|journal=Journal of Arachnology|volume=39|issue=1|pages=154–160|doi=10.1636/p10-25.1|s2cid=55786642|issn=0161-8202|url=https://www.biodiversitylibrary.org/part/229280}}</ref> In addition to sexual cannibalism, ''Latrodectus hesperus'' are also known to engage in sibling cannibalism.<ref>{{cite journal|last1=Johnson|first1=J. Chadwick|last2=Kitchen|first2=Kathryn|last3=Andrade|first3=Maydianne C. B.|date=August 2010|title=Family Affects Sibling Cannibalism in the Black Widow Spider, Latrodectus hesperus|journal=Ethology|doi=10.1111/j.1439-0310.2010.01792.x|issn=0179-1613|volume=116|issue=8|pages=770–777|bibcode=2010Ethol.116..770J }}</ref>

Like other members of the Theridiidae, widow spiders construct a web of irregular, tangled, sticky silken fibres. Black widow spiders prefer to nest near the ground in dark and undisturbed areas, usually in small holes produced by animals, or around construction openings or woodpiles. Indoor nests are in dark, undisturbed places such as under desks or furniture or in a basement.<ref>{{cite web|title=Black Widow Spider - Facts, Bite & Habitat Information|url=https://animalcorner.co.uk/animals/black-widow-spider/|website=Animal Corner|access-date=4 November 2016}}</ref> The spider frequently hangs upside down near the centre of its web and waits for insects to blunder in and get stuck. Then, before the insect can extricate itself, the spider rushes over to envenomate and wrap it in silk. To feed, the spider's mouth pulses [[digestive juice]]s over the prey, which liquifies, which the spider internalizes by [[capillary action]], sucking the slurry into its mouth.<ref name="Eberhard">{{cite journal |last1=Eberhard |first1=W G |title=The mystery of how spiders extract food without masticating prey |journal=Bulletin of the British Arachnological Society |date=2006 |volume=13 |issue=9 |pages=372–6|url=http://britishspiders.org.uk/bulletin/130908.pdf}}</ref><ref name="natgeo">{{cite web|title=Black Widow Spiders|url=https://www.nationalgeographic.com/animals/invertebrates/group/black-widow-spiders/?beta=true|archive-url=https://web.archive.org/web/20180612141134/https://www.nationalgeographic.com/animals/invertebrates/group/black-widow-spiders/?beta=true|url-status=dead|archive-date=June 12, 2018|website=National Geographic|access-date=19 June 2017|date=10 September 2010}}</ref> Their prey consists of small insects such as flies, mosquitoes, grasshoppers, beetles, and caterpillars.<ref name="natgeo"/> If the spider perceives a threat, it quickly lets itself down to the ground on a safety line of silk.

As with other web-weavers, these spiders have very poor eyesight and depend on vibrations reaching them through their webs to find trapped prey or warn them of larger threats. When a widow spider is trapped, it is unlikely to bite, preferring to play dead or flick silk at the potential threat; bites occur when they cannot escape.<ref>{{cite journal|last1=Nelsen|first1=David|last2=Kelln|first2=Wayne|last3=Hayes|first3=William|title=Poke but don't pinch: risk assessment and venom metering in the western black-widow spider, Latrodectus hesperus|doi=10.1016/j.anbehav.2013.12.019|volume=89|journal=Animal Behaviour|pages=107–114|year=2014|s2cid=53166675}}</ref> Many injuries to humans are due to defensive bites delivered when a spider gets unintentionally squeezed or pinched. The blue mud dauber species, ''[[Chalybion californicum]]'', is a wasp that, in western North America, is the primary predator of black widow spiders.<ref>{{cite book|chapter-url=http://insects.tamu.edu/fieldguide/cimg334.html|chapter=Mud Daubers|publisher=[[Gulf Publishing Company]]|year=1999|title=Field Guide to Texas Insects|first1=Bastiaan M.|last1=Drees|first2=John A.|last2=Jackman|access-date=10 July 2007|isbn=978-0-87719-263-3|archive-date=12 July 2007|url-status=dead|archive-url=https://web.archive.org/web/20070712045134/http://insects.tamu.edu/fieldguide/cimg334.html}}</ref>

The [[Tensile strength#Explanation|ultimate tensile strength]] and other physical properties of ''[[Latrodectus hesperus]]'' (western black widow) silk are similar to the properties of silk from [[orb-weaving spider]]s that had been tested in other studies. The tensile strength for the three kinds of silk measured in the Blackledge study was about 1,000&nbsp;MPa. The ultimate strength reported in a previous study for ''[[Trichonephila edulis]]'' was 1,290&nbsp;±&nbsp;160&nbsp;MPa.<ref>{{cite journal|last1=Blackledge|first1=T. A.|last2=Swindeman|first2=John E.|last3=Hayashi|first3=Cheryl Y.|title=Quasistatic and continuous dynamic characterization of the mechanical properties of silk from the cobweb of the black-widow spider ''Latrodectus hesperus''|journal=Journal of Experimental Biology|date=15 May 2005|volume=208|issue=10|pages=1937–1949|url=http://jeb.biologists.org/content/jexbio/208/10/1937.full.pdf#page=11|doi=10.1242/jeb.01597|pmid=15879074|doi-access=free|bibcode=2005JExpB.208.1937B }}</ref> The tensile strength of spider silk is comparable to that of steel wire of the same thickness.<ref>{{cite web
 |title=Astm a36
 |publisher=OnlineMetals.com
 |url=http://www.onlinemetals.com/alloycat.cfm?alloy=A36
 |url-status=dead
 |archive-url=https://web.archive.org/web/20130509100958/http://www.onlinemetals.com/alloycat.cfm?alloy=A36
 |archive-date=9 May 2013}}</ref>{{Failed verification|date=June 2017}} However, as the density of steel is about six times that of silk,<ref>{{cite journal
 |last1=Elices
 |first1=Manuel
 |title=Finding Inspiration in Argiope Trifasciata Spider Silk Fibers
 |doi=10.1007/s11837-005-0218-7
 |bibcode=2005JOM....57b..60E
 |url=http://www.tms.org/pubs/journals/JOM/0502/Elices-0502.html
 |access-date=2009-01-23
 |year=2005
 |last2=Guinea
 |first2=Gustavo V.
 |last3=Pérez-Rigueiro
 |first3=José
 |last4=Plaza
 |first4=Gustavo R.
 |journal=JOM
 |volume=57
 |issue=2
 |pages=60–66
 |s2cid=136722925
 |display-authors=etal
 |archive-url=https://web.archive.org/web/20090115152853/http://www.tms.org/pubs/journals/JOM/0502/Elices-0502.html
 |archive-date=2009-01-15
 |url-status=dead
 |url-access=subscription
 }}</ref> silk is correspondingly stronger than steel wire of the same weight.

Spiders of the genus ''[[Steatoda]]'' (also of the Theridiidae) are often mistaken for widow spiders, and are known as "[[false widow spider]]s"; while their bite can be painful, they are significantly less harmful to humans.

==Taxonomy==
[[File:Latrodectus.elegans.male.-.tanikawa.jpg|thumb|Male ''L.&nbsp;elegans'' from Japan]]
[[File:blackwidow macro.jpg|thumb|200px|right|''L. hesperus'' hair and markings]]
[[File:Black Widow spider, Female.jpg|thumb|''L. hesperus'' profile]]
[[File:Brown widow spider Latrodectus geometricus underside.jpg|thumb|Ventral side of a ''L.&nbsp;geometricus'' displaying the hourglass marking]]
[[File:Brown widow spider Latrodectus geometricus backside.jpg|thumb|Dorsal side of a ''L.&nbsp;geometricus'' in [[Colorado]], United States]]
[[File:Blackwidow eggsac silk.jpg|thumb|''L. hesperus'' with egg sac]]
[[File:Latrodectus tredecimguttatus female.jpg|thumb|''[[Latrodectus tredecimguttatus|L. tredecimguttatus]]'' (female swollen with eggs)]]

The genus ''Latrodectus'' was erected by [[Charles Athanase Walckenaer]] in 1805, for the species ''[[Latrodectus tredecimguttatus]]'' and ''[[Latrodectus mactans]]''.<ref name=WSC_g3502/><ref name=Walc05>{{cite book |last1=Walckenaer |first1=C.A. |date=1805 |title=Tableau des aranéides ou caractères essentiels des tribus, genres, familles et races que renferme le genre Aranea de Linné, avec la désignation des espèces comprises dans chacune de ces divisions |trans-title=Table of the aranid or essential characters of the tribes, genera, families and races contained in the genus Aranea de Linné, with the designation of the species included in each of these divisions |location=Paris |publisher=Dentu |pages=81–82}}</ref> Arachnologist [[Herbert Walter Levi]] revised the genus in 1959, studying the female sexual organs and noting their similarity across described species. He concluded the colour variations were variable across the world and were not sufficient to warrant species status, and reclassified the redback and several other species as subspecies of the black widow spider.<ref name="levi 1959">{{cite journal |last1=Levi |first1=Herbert W. |date=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>

Levi also noted that study of the genus had been contentious; in 1902, both [[Frederick Octavius Pickard-Cambridge|F. O. Pickard-Cambridge]] and [[Friedrich Dahl]] had revised the genus, with each criticising the other. Cambridge questioned Dahl's separating species on what he considered minor anatomical details, and the latter dismissed the former as an "ignoramus".<ref name="levi 1959" />

===Species===
{{as of|2023|11}} the [[World Spider Catalog]] accepted the following species:<ref name=WSC_g3502/>
*''[[Latrodectus antheratus]]'' <small>(Badcock, 1932)</small> – [[Paraguay]], [[Argentina]]
*''[[Latrodectus apicalis]]'' <small>[[Arthur Gardiner Butler|Butler]], 1877</small> – [[Galápagos Islands|Galapagos Islands]]
*''[[Latrodectus bishopi]]'' <small>[[B. J. Kaston|Kaston]], 1938</small> – [[United States|US]]
*''[[Latrodectus cinctus]]'' <small>[[John Blackwall|Blackwall]], 1865</small> – [[Cape Verde]], [[Africa]], [[Kuwait]], [[Iran]]
*''[[Latrodectus corallinus]]'' <small>Abalos, 1980</small> – Argentina
*''[[Latrodectus curacaviensis]]'' <small>(Müller, 1776)</small> – [[Lesser Antilles]], [[South America]]
*''[[Latrodectus dahli]]'' <small>[[Herbert Walter Levi|Levi]], 1959</small> – North Africa, [[Cyprus]], [[Turkey]], [[Azerbaijan]], [[Kazakhstan]], [[Middle East]], Iran, [[Central Asia]]
*''[[Latrodectus diaguita]]'' <small>Carcavallo, 1960</small> – Argentina
*''[[Latrodectus elegans]]'' <small>[[Tamerlan Thorell|Thorell]], 1898</small> – [[India]], [[Myanmar]], [[Thailand]], [[China]], [[Japan]]
*''[[Latrodectus erythromelas]]'' <small>[[Günter Schmidt (arachnologist)|Schmidt]] & Klaas, 1991</small> – India, [[Sri Lanka]]
*''[[Latrodectus garbae]]'' <small>Rueda & Realpe, 2021</small> – [[Colombia]]
*''[[Latrodectus geometricus]]'' <small>[[Ludwig Carl Christian Koch|C. L. Koch]], 1841</small> – Africa. Introduced to both Americas, [[Poland]], Middle East, [[Pakistan]], India, Thailand, Japan, China, [[Papua New Guinea]], [[Australia]], [[Hawaii]]
*''[[Latrodectus hasselti]]'' <small>Thorell, 1870</small> – [[Southeast Asia]] to Australia. Introduced to Iran, Pakistan, India, Japan, [[New Zealand]]
*''[[Latrodectus hesperus]]'' <small>[[Ralph Vary Chamberlin|Chamberlin]] & [[Wilton Ivie|Ivie]], 1935</small> – [[Canada]], US, [[Mexico]]. Introduced to [[Israel]], [[Korea]]
*''[[Latrodectus hurtadoi]]'' <small>Rueda & Realpe, 2021</small> – Colombia
*''[[Latrodectus hystrix]]'' <small>[[Eugène Simon|Simon]], 1890</small> – [[Yemen]] (mainland, [[Socotra]])
*''[[Latrodectus indistinctus]]'' <small>[[Octavius Pickard-Cambridge|O. Pickard-Cambridge]], 1904</small> – [[Namibia]], [[South Africa]]
*''[[Latrodectus karrooensis]]'' <small>Smithers, 1944</small> – South Africa
*''[[Latrodectus katipo]]'' <small>Powell, 1871</small> – New Zealand
*''[[Latrodectus lilianae]]'' <small>Melic, 2000</small> – [[Spain]], [[Algeria]]?
*''[[Latrodectus mactans]]'' <small>([[Johan Christian Fabricius|Fabricius]], 1775)</small> – Probably native to [[North America]] only. Introduced to South America, [[Asia]]
*''[[Latrodectus menavodi]]'' <small>Vinson, 1863</small> – [[Madagascar]], [[Comoros]], [[Seychelles]] (Aldabra)
*''[[Latrodectus mirabilis]]'' <small>(Holmberg, 1876)</small> – Argentina
*''[[Latrodectus obscurior]]'' <small>[[Friedrich Dahl|Dahl]], 1902</small> – Cape Verde Is., [[Madagascar]]
*''[[Latrodectus occidentalis]]'' <small>Valdez-Mondragón, 2023</small> – Mexico
*''[[Latrodectus pallidus]]'' <small>O. Pickard-Cambridge, 1872</small> – Cape Verde Is. to [[Libya]], Turkey, Kazakhstan, Iran, Central Asia
*''[[Latrodectus quartus]]'' <small>Abalos, 1980</small> – Argentina
*''[[Latrodectus renivulvatus]]'' <small>Dahl, 1902</small> – Africa, Yemen, [[Saudi Arabia]], [[Iraq]]
*''[[Latrodectus revivensis]]'' <small>Shulov, 1948</small> – [[Israel]], [[Iran]], possibly the [[Canary Islands]]
*''[[Latrodectus rhodesiensis]]'' <small>Mackay, 1972</small> – [[Southern Africa]]
*''[[Latrodectus thoracicus]]'' <small>Nicolet, 1849</small> – [[Chile]]
*''[[Latrodectus tredecimguttatus]]'' <small>(Rossi, 1790)</small> ([[Type species|type]]) – Mediterranean, [[Ukraine]], [[Caucasus]], [[Russia]] (Europe to South Siberia), Kazakhstan, Iran, Central Asia, China
*''[[Latrodectus umbukwane]]'' <small>B. M. O. G. Wright, C. D. Wright, Lyle & Engelbrecht, 2019</small> – South Africa
*''[[Latrodectus variegatus]]'' <small>Nicolet, 1849</small> – Chile, Argentina
*''[[Latrodectus variolus]]'' <small>Walckenaer, 1837</small> – US, [[Canada]]

'''[[Nomen dubium|Nomina dubia]]'''
*''L. dotatus'' <small>C. L. Koch, 1841</small>
*''L. limacidus'' <small>Cantor, 1842</small>
*''L. pallidus'' <small>Caporiacco, 1933</small>

==Distribution==
Widow spiders are found on every continent of the world except Antarctica. In North America, the black widows commonly known as southern (''[[Latrodectus mactans]]''), western (''[[Latrodectus hesperus]]''), and northern (''[[Latrodectus variolus]]'') are found in the United States, equally in western [[Mexico]] (''[[Latrodectus occidentalis]]''), as well as parts of southern Canada&nbsp;– particularly in the [[Okanagan Valley]] of British Columbia, as are the "grey" or "brown widow spiders" (''[[Latrodectus geometricus]]'') and the "red widow spiders" (''[[Latrodectus bishopi]]'').<ref>Preston-Malfham, 1998.</ref>

The most prevalent species occurring in eastern Asia and Australia is commonly called the redback (''[[Latrodectus hasselti]]'').

They are often confused with spiders in the genus ''[[Steatoda]]'', known as false widow spiders, due to their similar appearance.<ref>{{Cite web|title=Poisonous false widow spiders spread across Ireland|url=https://www.independent.ie/world-news/poisonous-false-widow-spiders-spread-across-ireland-29668336.html|access-date=2020-12-15|website=independent|date=17 October 2013 |language=en}}</ref>

==Venom==
{{Main|Latrodectism}}
Due to the presence of [[latrotoxin]] in their venom, black widow bites are potentially dangerous and may result in systemic effects ([[latrodectism]]) including severe muscle pain, abdominal cramps, [[diaphoresis]], [[tachycardia]], and muscle spasms.<ref name="ushkaryov171">{{Cite book |last1=Ushkaryov |first1=YA |last2=Rohou |first2=A |last3=Sugita |first3=S |title=alpha-Latrotoxin and its receptors |year=2008 |issue=184 |pages=171–206 |pmid=18064415 |doi=10.1007/978-3-540-74805-2_7 |pmc=2519134 |volume=184 |series=Handbook of Experimental Pharmacology |isbn=978-3-540-74804-5}}</ref> Symptoms usually last for 3–7 days, but may persist for several weeks.<ref name="peterson187">{{cite journal |last=Peterson |first=ME |title=Black widow spider envenomation |journal=Clinical Techniques in Small Animal Practice |date=November 2006 |volume=21 |issue=4 |pages=187–90 |pmid=17265903 |doi=10.1053/j.ctsap.2006.10.003}}</ref> In 1933, a [[University of Alabama]] medical faculty, [[Allan Blair]] conducted an experiment on himself to document the symptoms of a black widow bite, and to test whether someone can build immunity after being bitten.<ref>{{cite web|date=2015-06-23|title=Would you let a black widow bite you for science?|url=https://www.al.com/news/2015/06/how_a_ua_doctor_allowed_a_blac.html|access-date=2020-11-30|website=al|language=en}}</ref> The effects of the bite were so painful and harsh that Blair failed to complete the experiment and did not follow through with being bitten a second time.

In the United States each year, about 2,500<ref>{{cite journal |url=https://pubmed.ncbi.nlm.nih.gov/31492593/ |last1=Halmo |first1=Laurie Seidel |last2=Hurst |first2=Irene A. |last3=Ng |first3=Patrick C. |last4=Wang |first4=George Sam |title=Latrodectus Facies After Latrodectus Hesperus Envenomation in a Pediatric Patient |journal=The Journal of Emergency Medicine |year=2019 |volume=57 |issue=4 |pages=523–526 |publisher=ELSEVIER SCIENCE INC |doi=10.1016/j.jemermed.2019.06.018 |pmid=31492593 |s2cid=201868835 |access-date=20 April 2023}}</ref> people report being bitten by a black widow, but most do not need medical treatment. Some bites have no venom injected—⁠a "dry" bite. In the United States, no deaths due to black widows have been reported to the American Association of Poison Control Centers since 1983.<ref>{{cite journal |last1=Mowry |first1=James B. |last2=Spyker |first2=Daniel A. |last3=Cantilena |first3=Louis R. |last4=Bailey |first4=J. Elise |last5=Ford |first5=Marsha |date=December 2013 |title=2012 Annual Report of the American Association of Poison Control Centers' National Poison Data System (NPDS): 30th Annual Report |url=https://aapcc.s3.amazonaws.com/pdfs/annual_reports/2012_NPDS_Annual_Report.pdf |journal=Clinical Toxicology |language=en |volume=51 |issue=10 |pages=949–1229 |doi=10.3109/15563650.2013.863906 |pmid=24359283 |s2cid=43129572 |issn=1556-3650}}</ref>{{failed verification|date=April 2025}} Black widows are not especially aggressive spiders, and they rarely bite humans unless startled or otherwise threatened.<ref>[http://www.livescience.com/49333-why-black-widow-spider-venom-is-so-potent.html Why Black Widow Spider Venom Is So Potent]. By Jennifer Viegas, ''Discovery News'' January 6, 2015.</ref>

Contrary to popular assumptions, most people who are bitten suffer no serious damage, let alone death. Fatal bites were reported in the early 20th century mostly with ''[[Latrodectus tredecimguttatus]]'', the Mediterranean black widow.<ref>{{cite journal |last1=Bettini |first1=S |year=1964 |title=Epidemiology of latrodectism |journal=Toxicon |volume=2 |issue=2|pages=93–102 |doi=10.1016/0041-0101(64)90009-1 |pmid=14301291|bibcode=1964Txcn....2...93B }}</ref>

Since the venom is not usually life-threatening, [[antivenom]] has been used as [[Analgesic|pain relief]] and not to save lives.<ref name="raveii">{{cite journal|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.|title=Randomized Controlled Trial of Intravenous Antivenom Versus Placebo for Latrodectism: The Second Redback Antivenom Evaluation (RAVE-II) Study|journal=Annals of Emergency Medicine|date=2014|doi=10.1016/j.annemergmed.2014.06.006|pmid=24999282|volume=64|issue=6|pages=620–8.e2|hdl=2123/14928|hdl-access=free}}</ref> However, a study demonstrated that standardized [[Analgesic|pain medication]], when combined with either antivenom or a placebo, had similar improvements in pain and resolution of symptoms.<ref name="raveii" />

==See also==
* [[List of medically significant spider bites]]

==References==
{{Reflist|refs=
<ref name=WSC_g3502>{{cite web |title=Gen. ''Latrodectus'' Walckenaer, 1805 |work=World Spider Catalog |publisher=Natural History Museum Bern |url=http://www.wsc.nmbe.ch/genus/3502 |access-date=2016-01-28}}</ref>

<ref name=WSC_sl3502>{{cite web |title=Species list for ''Latrodectus'' |website=World Spider Catalog |publisher=Natural History Museum Bern |url=http://www.wsc.nmbe.ch/specieslist/3502 |access-date=2016-01-28}}</ref>
}}

==Further reading==
*{{cite book |title=The Book of the Spiders |url=https://archive.org/details/bookofspidercomp0000hill |url-access=registration |last=Hillyard |first=Paul |year=1994 |publisher=Avon Books |location=New York |pages=[https://archive.org/details/bookofspidercomp0000hill/page/22 22–35]|isbn=9780380730759}}
*{{cite book |title=Black Widow Spiders |last=Martin |first=Louise |year=1988 |publisher=Rourke Enterprises, Inc. |pages=18–20}}
*{{cite book |title=Spiders |last=Preston-Malfham |first=Ken |year=1998 |publisher=Chartwell Books |location=Edison, New Jersey |page=40}}
*{{cite journal |last=Abalos |first=J. W. |title=The egg-sac in the Identification of Species of ''Latrodectus'' (Black-Widow Spiders) |journal=Psyche: A Journal of Entomology |year=1962 |volume=69 |issue=4 |pages=268–270 |doi=10.1155/1962/36967 |doi-access=free |url=http://downloads.hindawi.com/journals/psyche/1962/036967.pdf |access-date=September 26, 2013}}
*{{cite journal |title=North American Widow Spiders of the ''Latrodectus curacaviensis'' Group |journal=Psyche: A Journal of Entomology |volume=71 |issue=1 |pages=12–27 |last1=Levi |first1=H. W. |last2=McCrone |first2=J. D. |year=1964|doi=10.1155/1964/86469 |doi-access=free}}

==External links==
{{wiktionary | Latrodectus}}
{{Commons-inline|Latrodectus|''Latrodectus''}}
*[http://tolweb.org/Latrodectus/93274 Tree of Life: ''Latrodectus'' ]
*[http://www.european-arachnology.org/wdp/wp-content/uploads/2015/08/215-222_Schmidt.pdf Description of crossing experiments between various ''Latrodectus'' species]
*[https://entnemdept.ufl.edu/creatures/beneficial/wasps/latrodectus_parasitoids.htm Widow spider parasitoids] on the [[University of Florida|UF]] / [[Institute of Food and Agricultural Sciences|IFAS]] Featured Creatures Web site

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[[Category:Latrodectus| ]]
[[Category:Araneomorphae genera]]
[[Category:Cosmopolitan spiders]]
[[Category:Venomous arthropods]]