Contents 1 Taxonomy 2 Description 3 Range 4 Reproduction 5 Prey 6 Natural enemies 7 Toxicology 8 References 9 External links

Taxonomy[edit] Latrodectus mactans was first described by Johan Christian Fabricius in 1775, placing it in the genus Aranea.[1][3] It was transferred to the genus Latrodectus in 1837 by Charles Walckenaer and is currently placed in the Theridiidae family of the order Araneae.[1] The species is closely related to Latrodectus hesperus (western black widow) and Latrodectus variolus (northern black widow). Members of the three species are often confused with the genus Steatoda, the false widows. Prior to 1970, when the current taxonomic divisions for North American black widows were set forth by Kaston,[4] all three varieties were classified as a single species, L. mactans. As a result, there exist numerous references which claim that "black widow" (without any geographic modifier) applies to L. mactans alone. Common usage of the term "black widow" makes no distinction between the three species.

Description[edit] The body length (excluding legs) of the mature female is 8–13 mm (0.31–0.51 in), 3–6 mm (0.12–0.24 in) for males. Legs are long in proportion to body.[5] Females are shiny and black in color, with a red marking in the shape of an hourglass on the ventral (under) side of her very rounded abdomen.[6] There is much variation in female size, particularly in egg-carrying (gravid) females. The abdomen of a gravid female can be more than 1.25 cm (0.5 in) in diameter. Many female widows also have an orange or red patch just above the spinnerets on the top of the abdomen.[7] Juveniles have a distinctly different appearance from the adults; the abdomen is grayish to black with white stripes running across it and is spotted with yellow and orange.[7] Males are either purple, or closer to the appearance of the juveniles in color. The web of the black widow spider is a three-dimensional tangled cobweb of exceptionally strong silk.[8] The distinctive red hourglass marking

Range[edit] The southern widow is primarily found in (and is indigenous to) the southeastern United States, ranging as far north as Ohio and as far west as Texas.[9] The northern black widow (L. variolus) is found primarily in the northeastern United States and southeastern Canada, though its range overlaps with that of L. mactans. In Canada, black widows range in the southern parts of British Columbia, Alberta, Saskatchewan, Manitoba and Ontario.[10] In the Dominican Republic it is found throughout the whole country.[11][12] Latrodectus mactans, along with Latrodectus hesperus and Latrodectus geometricus (the "brown widow spider"), is established in the Hawaiian Islands (USA).[13][14] One pathway of entry into Hawaii for at least one of these black widow species is imported produce[15] (which is also considered an important potential pathway for widow spiders elsewhere[16]).

Reproduction[edit] When a male is mature, he spins a sperm web, deposits semen on it, and charges his palpal bulbs with the sperm. Black widow spiders reproduce sexually when the male inserts his palpal bulbs into the female's spermathecal openings. The female deposits her eggs in a globular silken container in which they remain camouflaged and guarded. A female black widow spider can produce four to nine egg sacs in one summer, each containing about 100–400 eggs. Usually, eggs incubate for twenty to thirty days. It is rare for more than a hundred to survive this process. On average, thirty will survive through the first molting, because of cannibalism, lack of food, or lack of proper shelter. It takes two to four months for black widow spiders to mature enough to breed, however full maturation typically takes six to nine months. The females can live for up to three years, while a male's lifespan is about three to four months.[17] The female may eat the male after mating.

Prey[edit] Black widow spiders typically prey on a variety of insects, but occasionally they do feed on woodlice, diplopods, chilopods and other arachnids. The spider's web is even strong enough to catch animals as large as mice.[18] When the prey is entangled by the web, Latrodectus mactans quickly comes out of its retreat, wraps the prey securely in its strong web, then bites and envenoms its prey. The venom takes about ten minutes to take effect; in the meantime, the prey is held tightly by the spider. When movements of the prey cease, digestive enzymes are released into the wound. The black widow spider then carries its prey back to its retreat before feeding.[19]

Natural enemies[edit] There are various parasites and predators of widow spiders in North America, though apparently none of these have ever been evaluated in terms of augmentation programs for improved biocontrol. Parasites of the egg sacs include the flightless scelionid wasp Baeus latrodecti,[20] and members of the chloropid fly genus Pseudogaurax. Predators of the adult spiders include a few wasps, most notably the blue mud dauber, Chalybion californicum, and the spider wasp Tastiotenia festiva.[citation needed] Other species including Mantis or Centipede also will occasionally and opportunistically take widows as prey, but the preceding all exhibit some significant specific preference for Latrodectus.[citation needed] Furthermore, in 2012, researchers published a paper suggesting that the black widow's close relative, the brown widow, may be competing for territory with, and ultimately displacing black widows in Southern California.[21][22]

Toxicology[edit] Main article: Latrodectism See also: Spider bite Although the reputation of these spiders is notorious and their venom does affect humans, only mature females are capable of envenomation in humans; their chelicerae—the hollow, needle-like mouthparts that inject venom—are, at approximately 1 mm., or .04 in., long enough to inject venom into humans, unlike those of the much smaller males. The actual amount injected, even by a mature female, is variable. The venom injected by the female black widow is known as alpha-latrotoxin which binds to receptors at the neuromuscular motor end plate of both sympathetic and parasympathetic nerves, resulting in increased synaptic concentration of catecholamines. The symptoms are caused by lymphatic absorption and vascular dissemination of the neurotoxin. The symptoms that result from a black widow spider bite are collectively known as latrodectism. Deaths in healthy adults from Latrodectus bites are exceedingly rare, with no deaths despite two thousand bites yearly. On the other hand, the geographical range of the widow spiders is vast. Epidemics of mostly European Widow spider bites had been recorded from 1850 to 1950, and during that time period, deaths were reported from 2/1000 to 50/1000 bites. Deaths from the Western Black Widow had been reported as 50/1000 in the 1920s. At that same time, antivenom was introduced. [23] The LD-50 of L. mactans venom has been measured in mice as 1.39 mg/kg,[24] and separately as 1.30 mg/kg (with a confidence interval of 1.20–2.70).[25] In 1933, Allan Blair famously allowed himself to be bitten by the spider in order to investigate the toxicity of its venom in humans and as a means of convincing skeptics at the time who thought that the spider's venom might not be dangerous to humans. There are a number of active components in the venom: Latrotoxins A number of smaller polypeptides—toxins interacting with cation channels, which can affect the functioning of calcium, sodium, or potassium channels. Adenosine Guanosine Inosine 2,4,6-trihydroxypurine. The venom is neurotoxic.

References[edit] ^ a b c "Taxon details Latrodectus mactans (Fabricius, 1775)", World Spider Catalog, Natural History Museum Bern, retrieved 2016-01-28  ^ "Archived copy". Archived from the original on 21 August 2011. Retrieved 19 July 2008.  ^ Fabricius, J. C. 1775. Systema entomologiae, sistens insectorum classes, ordines, genera, species, adiectis, synonymis, locis descriptionibus observationibus. Flensburg and Lipsiae, 832 pp. (Araneae, pp. 431–441). [432] ^ Kaston, B. J. (1970). "Comparative biology of American black widow spiders". Transactions of the San Diego Society of Natural History. 16 (3): 33–82.  ^ mactans (Southern Black Widow) ^ "Southern black widow spider". Archived from the original on 9 March 2009. Retrieved 10 March 2009.  ^ a b "Widow Spiders". Archived from the original on 18 October 2008. Retrieved 18 February 2009.  ^ "Black Widows Spin Super Silk. Science News". 1996-12-31. Retrieved 2016-01-08.  ^ Southern black widow spider ^ "Archived copy". Archived from the original on 31 March 2012. Retrieved 2011-09-25.  ^ Marion H., Luis (3 February 1980). "Aracnoidismo en la Republica Dominicana" (PDF). Medicina al Dia (in Spanish). BVS. Archived from the original (PDF) on 3 November 2013. Retrieved 8 October 2012.  ^ Inirio, Juan Ramon (2009-11-06). "Detectan la peligrosa viuda negra". El Nacional (in Spanish). Retrieved 2012-10-08.  ^ Tenorio, Joanne M., and Gordon M. Nishida. 1995. What's Bugging Me? Identifying and Controlling Household Pests in Hawaii. University of Hawaii Press (Honolulu). 184+7 pp. illus. (publisher's listing) ^ Scott, Susan, and Craig Thomas, M.D. 2000. Pest of Paradise: First Aid and Medical Treatment of Injuries from Hawaii's Animals. University of Hawaii Press (Honolulu). 190+xii pp. illus. (publisher's listing) ^ Honolulu Star-Bulletin. 6 November 2008. Creepy critter caught in grapes. ^ Import Health Standard Commodity Sub-class: Fresh Fruit/Vegetables Table grapes, (Vitis vinifera) from the United States of America—State of California (Issued pursuant to Section 22 of the (New Zealand) Biosecurity Act 1993; Date Issued: 18 August 2005). ^ "Black Widow Spiders". DesertUSA.  ^ Latrodetus Mactans McCorkle, Matthew. 17 October 2002. ^ Foelix, R. (1982). Biology of Spiders, pp. 162–163. Harvard University, U.S. ^ Bibbs, Christopher; Buss, Lyle (August 2015) [2012]. "Widow Spider Parasitoids Philolema latrodecti" (PDF). University of Florida. Retrieved 16 March 2017.  ^ Are Brown Widow Spiders Displacing Black Widows?. ^ Vetter, RS; Vincent, LS; Danielsen, DW; Reinker, KI; Clarke, DE; Itnyre, AA; Kabashima, JN; Rust, MK (2012). "The prevalence of brown widow and black widow spiders (Araneae: Theridiidae) in urban southern California". J. Med. Entomol. 49: 947–51. doi:10.1603/me11285. PMID 22897057.  ^ Bettini, S (1964). "Epidemiology of latrodectism". Toxicon. 2: 93–101. doi:10.1016/0041-0101(64)90009-1. PMID 14301291.  ^ Rauber, Albert (1 January 1983). "Black Widow Spider Bites". Clinical Toxicology. 21 (4–5): 473–485. doi:10.3109/15563658308990435. PMID 6381753.  ^ McCrone, J.D. (1 December 1964). "Comparative lethality of several Latrodectus venoms". Toxicon. 2 (3): 201–203. doi:10.1016/0041-0101(64)90023-6. 

External links[edit] Wikispecies has information related to Latrodectus mactans Wikimedia Commons has media related to Latrodectus mactans. Fact Sheet on the Black Widow Spider includes information on habits, habitat and threats Latrodectus Mactans on Pterodattilo University of Washington Burke Museum spider myths Black Widow Spider Venom and Bites Intoxication Treatment Information on black widow spider bite in eMedicineHealth Latrodectus mactans on the UF / IFAS Featured Creatures website. Taxon identifiers Wd: Q113297 ADW: Latrodectus_mactans ARKive: latrodectus-mactans BugGuide: 26336 EoL: 1187519 Fauna Europaea: 353290 GBIF: 2157949 iNaturalist: 47381 ITIS: 859138 NCBI: 6924 WSC: Retrieved from "" Categories: LatrodectusVenomous spidersSpiders of North AmericaFauna of the CaribbeanFauna of the California chaparral and woodlandsFauna of the Southeastern United StatesFauna of the Western United StatesSpiders described in the 18th centurySpiders described in 1775Hidden categories: CS1 Spanish-language sources (es)Use dmy dates from February 2013Articles with 'species' microformatsAll articles with unsourced statementsArticles with unsourced statements from April 2017Articles with unsourced statements from January 2016

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Taxonomy (biology)EAnimalArthropodChelicerataArachnidSpiderAraneomorphaeTheridiidaeLatrodectusBinomial NomenclatureJohan Christian FabriciusWikipedia:Citation NeededLatrodectusJohan Christian FabriciusAraneusCharles Athanase WalckenaerTheridiidaeAraneaeLatrodectus HesperusLatrodectus VariolusSteatodaNorth AmericaHourglassAnatomical Terms Of LocationAbdomenEnlargeSoutheastern United StatesOhioTexasNorthern Black WidowNortheastern United StatesCanadaBritish ColumbiaAlbertaSaskatchewanManitobaOntarioDominican RepublicLatrodectus HesperusLatrodectus GeometricusHawaiian IslandsHawaiiPalpal BulbEcdysisCannibalism (zoology)WoodliceDiplopodsChilopodsArachnidsParasitePredatorNorth AmericaBiocontrolScelionidaeChloropidaePseudogauraxMud DauberChalybion CalifornicumSpider WaspWikipedia:Citation NeededMantisCentipedeLatrodectusWikipedia:Citation NeededBrown WidowLatrodectismSpider BiteLatrodectismAntivenomLD-50Allan BlairLatrotoxinPolypeptidesCationAdenosineGuanosineInosineNeurotoxinDigital Object IdentifierPubMed IdentifierDigital Object IdentifierPubMed IdentifierDigital Object IdentifierPubMed IdentifierDigital Object IdentifierWikispeciesUFInstitute Of Food And Agricultural SciencesHelp:Taxon IdentifiersWikidataAnimal Diversity WebARKiveBugGuideEncyclopedia Of LifeFauna EuropaeaGlobal Biodiversity Information FacilityINaturalistIntegrated Taxonomic Information SystemNational Center For Biotechnology InformationWorld Spider CatalogHelp:CategoryCategory:LatrodectusCategory:Venomous SpidersCategory:Spiders Of North AmericaCategory:Fauna Of The CaribbeanCategory:Fauna Of The California Chaparral And WoodlandsCategory:Fauna Of The Southeastern United StatesCategory:Fauna Of The Western United StatesCategory:Spiders Described In The 18th CenturyCategory:Spiders Described In 1775Category:CS1 Spanish-language Sources (es)Category:Use Dmy Dates From February 2013Category:Articles With 'species' MicroformatsCategory:All Articles With Unsourced StatementsCategory:Articles With Unsourced Statements From April 2017Category:Articles With Unsourced Statements From January 2016Discussion About Edits From This IP Address [n]A List Of Edits Made From This IP Address [y]View The Content Page [c]Discussion About The Content Page [t]Edit This Page [e]Visit The Main Page [z]Guides To Browsing WikipediaFeatured Content – The Best Of WikipediaFind Background Information On Current EventsLoad A Random Article [x]Guidance On How To Use And Edit WikipediaFind Out About WikipediaAbout The Project, What You Can Do, Where To Find ThingsA List Of Recent Changes In The Wiki [r]List Of All English Wikipedia Pages Containing Links To This Page [j]Recent Changes In Pages Linked From This Page [k]Upload Files [u]A List Of All Special Pages [q]Wikipedia:AboutWikipedia:General Disclaimer

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