The recluse spiders (''Loxosceles'' (), also known as brown spiders, fiddle-backs, violin spiders, and reapers, is a genus of spiders that was first described by R. T. Lowe in 1832. They are venomous spiders known for their bite, which sometimes produces a characteristic set of symptoms known as loxoscelism. Recluse spiders are now identified as members of the family Sicariidae, having formerly been placed in their own family, the Loxoscelidae. Although recluse spiders are feared, they are usually not aggressive.

Relation with other spiders

Sicariidae are of the superfamily Scytodoidea. Other families in the Scytodoidea include Drymusidae, Scytodidae, and Periegopidae.

Habitat and appearance

''Loxosceles'' is distributed nearly worldwide in warmer areas. All have six eyes arranged in three groups of two (dyads) and some are brownish with a darker brown characteristic violin marking on the

cephalothorax The cephalothorax, also called prosoma in some groups, is a tagma of various arthropods, comprising the head and the thorax fused together, as distinct from the abdomen behind. (The terms ''prosoma'' and ''opisthosoma'' are equivalent to ''cepha ...

. However, the "violin marking" cannot be used as a reliable way to identify the spider as many unrelated species of spider have similar markings. Recluses are typically about 7–12 mm long. The most common and most famous species in the United States is the brown recluse spider (''Loxosceles reclusa''). It is found in a large area of the Midwest, west to Colorado and the New Mexico state line and east to northern Georgia. Sporadic records from other locations only represent incidental introductions, not established populations. The brown recluse feeds on whatever small prey is available, and has been observed to prefer scavenging over actively hunting. Other notable members of this genus include the Chilean recluse spider (''L. laeta'') and the Mediterranean recluse spider (''L. rufescens''). Recently, concerns have been raised regarding recluses spreading faster due to warmer air carrying them farther as a result of changing climate. On the contrary, newly hatched recluses do not travel via ballooning and thus the populations are confined to very tight spaces with dense populations. Most ''Loxosceles'' can live for one and a half to two years. Many species of this genus can live for very long times without food or water. Insecticides often fail to kill the spider, instead intoxicating its nervous system and inducing erratic behavior.

Identification

This genus is very hard to identify, as they have very simple coloration and morphology. Many other spiders have similar dorsal markings, leading to confusion and misidentification. They can be most readily distinguished by having 6 eyes, arranged in three pairs. None of the pairs of eyes touch each other, and are arranged in a U shape. The presence of two claws per foot and a rather flat

further help distinguish them.

Venom components and effects

''Loxosceles'' spiders, like '' Hexophthalma'' species, have potent tissue-destroying venoms containing the dermonecrotic agent which is otherwise found only in a few pathogenic bacteria. Recent research has indicated the venom is composed largely of sulfated nucleosides, though these compounds are relatively new discoveries, so little is known about them. The venom of several species is capable of producing necrotic lesions that are slow to heal and may require skin grafts. Rarely, the venom is carried by the bloodstream, causing red blood cell destruction. The venom is identical in male and female spiders, but females can have almost twice the concentration of toxins. For unknown reasons, the toxicity of the venom to mammalian species varies; recluse bites may cause necrosis in humans, rabbits, and guinea pigs, but not in mice or rats. The Chilean recluse (''L. laeta'') supposedly has a more potent venom, which results in systemic involvement more often. All ''Loxosceles'' species that have been tested have venoms similar to that of the brown recluse, and all should be avoided. In general, though, they are not aggressive and commonly occupy human dwellings without causing problems. Many types of skin wounds are mistaken for or assumed to be the result of a recluse spider bite. Several diseases can mimic the lesions of the bite, including Lyme disease, various fungal and bacterial infections, and the first sore of

syphilis Syphilis () is a sexually transmitted infection caused by the bacterium ''Treponema pallidum'' subspecies ''pallidum''. The signs and symptoms of syphilis vary depending in which of the four stages it presents (primary, secondary, latent, an ...

. It is important to associate the spider directly with the bite to avoid improper treatment, and to successfully treat common infections or other conditions if no spider was seen. Bites most often occur as a defense when the spider is trapped against the skin, in clothing, for example. The total volume of venom is minute (only 2 micrograms injected out of 4 microliters in the venom glands). The bite of a recluse spider can generally be categorized into one of the following groups: * Unremarkable – self-healing minute damage * Mild reaction – self-healing damage with itchiness, redness, patterns of aggressive behavior and a mild lesion. * Dermonecrotic – the uncommon, "classic" recluse bite, producing a necrotic skin lesion. About 66% of necrotic bite lesions heal with no complications. In extreme cases, the lesion may be up to 40 millimeters wide, last for several months, and heal with a permanent scar. * Systemic or viscerocutaneous – an extremely rare, systemic reaction to envenomation of the bloodstream. It is observed more often in children. Most bites are unremarkable or mild.

Species

it contains 143 species, found in Central America, the Caribbean, Oceania, Asia, Africa, North America, Europe, and South America: *'' L. accepta'' Chamberlin, 1920 – Peru *'' L. adelaida''

Gertsch Willis John Gertsch (October 4, 1906 – December 12, 1998) was an American arachnologist. He described over 1,000 species of spiders, scorpions, and other arachnids, including the Brown recluse spider and the Tooth cave spider. Gertsch was born ...

, 1967 – Brazil *'' L. alamosa'' Gertsch & Ennik, 1983 – Mexico *'' L. amazonica'' Gertsch, 1967 – Peru, Brazil *'' L. anomala'' ( Mello-Leitão, 1917) – Brazil *'' L. apachea'' Gertsch & Ennik, 1983 – USA, Mexico *'' L. aphrasta'' Wang, 1994 –

China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's most populous country, with a population exceeding 1.4 billion, slightly ahead of India. China spans the equivalent of five time zones and ...

*'' L. aranea'' Gertsch, 1973 – Mexico *'' L. arizonica'' Gertsch & Mulaik, 1940 – USA *'' L. aurea'' Gertsch, 1973 – Mexico *'' L. baja'' Gertsch & Ennik, 1983 – Mexico *'' L. barbara'' Gertsch & Ennik, 1983 – Mexico *'' L. belli'' Gertsch, 1973 – Mexico *'' L. bentejui'' Planas & Ribera, 2015 – Canary Is. *'' L. bergeri'' Strand, 1906 – Namibia *'' L. bettyae'' Gertsch, 1967 – Peru *'' L. blancasi'' Gertsch, 1967 – Peru *'' L. blanda'' Gertsch & Ennik, 1983 – USA *'' L. boneti'' Gertsch, 1958 – Mexico,

El Salvador El Salvador (; , meaning " The Saviour"), officially the Republic of El Salvador ( es, República de El Salvador), is a country in Central America. It is bordered on the northeast by Honduras, on the northwest by Guatemala, and on the south b ...

*'' L. candela'' Gertsch & Ennik, 1983 – Mexico *''Loxosceles carabobensis, L. carabobensis'' González-Sponga, 2010 – Venezuela *''Loxosceles cardosoi, L. cardosoi'' Rogério Bertani, Bertani, von Schimonsky & Gallão, 2018 – Brazil *''Loxosceles caribbaea, L. caribbaea'' Gertsch, 1958 – Greater Antilles *''Loxosceles carinhanha, L. carinhanha'' Bertani, von Schimonsky & Gallão, 2018 – Brazil *''Loxosceles carmena, L. carmena'' Gertsch & Ennik, 1983 – Mexico *''Loxosceles cederbergensis, L. cederbergensis'' Lotz, 2017 – South Africa *''Loxosceles chapadensis, L. chapadensis'' Bertani, Fukushima & Nagahama, 2010 – Brazil *''Loxosceles chinateca, L. chinateca'' Gertsch & Ennik, 1983 – Mexico *''Loxosceles coheni, L. coheni'' Alireza Zamani, Zamani, Mirshamsi & Yuri M. Marusik, Marusik, 2021 – southwestern IranAlireza Zamani, Omid Mirshamsi, Yuri M Marusik. 2021. ‘Burning Violin’: The Medically Important Spider Genus ''Loxosceles'' (Araneae: Sicariidae) in Iran, Turkmenistan, and Afghanistan, With Two New Species. ''Journal of Medical Entomology'', tjaa257, https://doi.org/10.1093/jme/tjaa257, Published: 10 December 2020. *''Loxosceles colima, L. colima'' Gertsch, 1958 – Mexico *''Loxosceles conococha, L. conococha'' Gertsch, 1967 – Peru *''Loxosceles coquimbo, L. coquimbo'' Gertsch, 1967 – Chile *''Loxosceles corozalensis, L. corozalensis'' González-Sponga, 2010 – Venezuela *''Loxosceles coyote, L. coyote'' Gertsch & Ennik, 1983 – Mexico *''Loxosceles cubana, L. cubana'' Gertsch, 1958 – Cuba, Bahama Is., HIspaniola *''Loxosceles cubiroensis, L. cubiroensis'' González-Sponga, 2010 – Venezuela *''Loxosceles curimaguensis, L. curimaguensis'' González-Sponga, 2010 – Venezuela *''Loxosceles dejagerae, L. dejagerae'' Lotz, 2017 – South Africa *''Loxosceles deserta, L. deserta'' Gertsch, 1973 – USA, Mexico *''Loxosceles devia, L. devia'' Gertsch & Mulaik, 1940 – USA, Mexico *''Loxosceles diaguita, L. diaguita'' Antônio Brescovit, Brescovit, Taucare-Ríos, Magalhaes & Santos, 2017 – Chile *''Loxosceles ericsoni, L. ericsoni'' Bertani, von Schimonsky & Gallão, 2018 – Brazil *''Loxosceles fontainei, L. fontainei'' Millot, 1941 – Guinea *''Loxosceles foutadjalloni, L. foutadjalloni'' Millot, 1941 – Guinea *''Loxosceles francisca, L. francisca'' Gertsch & Ennik, 1983 – Mexico *''Loxosceles frizzelli, L. frizzelli'' Gertsch, 1967 – Peru *''Loxosceles gaucho, L. gaucho'' Gertsch, 1967 – Brazil. Introduced to Tunisia *''Loxosceles gloria, L. gloria'' Gertsch, 1967 – Ecuador, Peru *''Loxosceles griffinae, L. griffinae'' Lotz, 2017 – Namibia *''Loxosceles guajira, L. guajira'' Cala-Riquelme, Gutiérrez-Estrada & Flórez, 2015 – Colombia *''Loxosceles guatemala, L. guatemala'' Gertsch, 1973 – Guatemala *''Loxosceles guayota, L. guayota'' Planas & Ribera, 2015 – Canary Is. *''Loxosceles haddadi, L. haddadi'' Lotz, 2017 – South Africa *''Loxosceles harrietae, L. harrietae'' Gertsch, 1967 – Peru *''Loxosceles herreri, L. herreri'' Gertsch, 1967 – Peru *''Loxosceles hirsuta, L. hirsuta'' Mello-Leitão, 1931 – Brazil, Paraguay, Argentina *''Loxosceles huasteca, L. huasteca'' Gertsch & Ennik, 1983 – Mexico *''Loxosceles hupalupa, L. hupalupa'' Planas & Ribera, 2015 – Canary Is. *''Loxosceles imazighen, L. imazighen'' Ribera & Massa, 2021 - Morocco *''Loxosceles immodesta, L. immodesta'' (Mello-Leitão, 1917) – Brazil *''Loxosceles inca, L. inca'' Gertsch, 1967 – Peru *''Loxosceles insula, L. insula'' Gertsch & Ennik, 1983 – Mexico *''Loxosceles intermedia, L. intermedia'' Mello-Leitão, 1934 – Brazil, Argentina *''Loxosceles irishi, L. irishi'' Lotz, 2017 – Namibia *''Loxosceles jaca, L. jaca'' Gertsch & Ennik, 1983 – Mexico *''Loxosceles jamaica, L. jamaica'' Gertsch & Ennik, 1983 – Jamaica *''Loxosceles jarmila, L. jarmila'' Gertsch & Ennik, 1983 – Jamaica *''Loxosceles julia, L. julia'' Gertsch, 1967 – Peru *''Loxosceles kaiba, L. kaiba'' Gertsch & Ennik, 1983 – USA *''Loxosceles karstica, L. karstica'' Bertani, von Schimonsky & Gallão, 2018 – Brazil *''Loxosceles lacroixi, L. lacroixi'' Millot, 1941 – Ivory Coast *''Loxosceles lacta, L. lacta'' Wang, 1994 – China *''Loxosceles laeta, L. laeta'' (Nicolet, 1849) – South America. Introduced to USA, Finland, Australia *''Loxosceles lawrencei, L. lawrencei'' Lodovico di Caporiacco, Caporiacco, 1955 – Venezuela, Trinidad, Curaçao *''Loxosceles lutea, L. lutea'' Eugen von Keyserling, Keyserling, 1877 – Colombia, Ecuador *''Loxosceles luteola, L. luteola'' Gertsch, 1973 – Mexico *''Loxosceles mahan, L. mahan'' Planas & Ribera, 2015 – Canary Is. *''Loxosceles maisi, L. maisi'' Sánchez-Ruiz & Brescovit, 2013 – Cuba *''Loxosceles makapanensis, L. makapanensis'' Lotz, 2017 – South Africa *''Loxosceles malintzi, L. malintzi'' Valdez-Mondragón, Cortez-Roldán, Juárez-Sánchez & Solís-Catalán, 2018 – Mexico *''Loxosceles manuela, L. manuela'' Gertsch & Ennik, 1983 – Mexico *''Loxosceles maraisi, L. maraisi'' Lotz, 2017 – Namibia *''Loxosceles martha, L. martha'' Gertsch & Ennik, 1983 – USA *''Loxosceles meruensis, L. meruensis'' Albert Tullgren, Tullgren, 1910 – Ethiopia, Kenya, Tanzania *''Loxosceles misteca, L. misteca'' Gertsch, 1958 – Mexico *''Loxosceles mogote, L. mogote'' Sánchez-Ruiz & Brescovit, 2013 – Cuba *''Loxosceles mrazig, L. mrazig'' Ribera & Planas, 2009 – Tunisia *''Loxosceles mulege, L. mulege'' Gertsch & Ennik, 1983 – Mexico *''Loxosceles muriciensis, L. muriciensis'' Fukushima, de Andrade & Bertani, 2017 – Brazil *''Loxosceles nahuana, L. nahuana'' Gertsch, 1958 – Mexico *''Loxosceles neuvillei, L. neuvillei'' Eugène Simon, Simon, 1909 – Ethiopia, Somalia, East Africa *''Loxosceles niedeguidonae, L. niedeguidonae'' de Andrade, Bertani, Nagahama & Barbosa, 2012 – Brazil *''Loxosceles olivaresi, L. olivaresi'' González-Sponga, 2010 – Venezuela *''Loxosceles olmea, L. olmea'' Gertsch, 1967 – Peru *''Loxosceles pallalla, L. pallalla'' Brescovit, Taucare-Ríos, Magalhaes & Santos, 2017 – Chile *''Loxosceles palma, L. palma'' Gertsch & Ennik, 1983 – USA, Mexico *''Loxosceles panama, L. panama'' Gertsch, 1958 – Panama *''Loxosceles parramae, L. parramae'' Newlands, 1981 – South Africa *''Loxosceles persica, L. persica'' Ribera & Alireza Zamani, Zamani, 2017 – Iran *''Loxosceles pilosa, L. pilosa'' William Frederick Purcell, Purcell, 1908 – Namibia, South Africa *''Loxosceles piura, L. piura'' Gertsch, 1967 – Peru *''Loxosceles pucara, L. pucara'' Gertsch, 1967 – Peru *''Loxosceles puortoi, L. puortoi'' Martins, Knysak & Bertani, 2002 – Brazil *''Loxosceles reclusa, L. reclusa'' Gertsch & Mulaik, 1940 – North America *''Loxosceles rica, L. rica'' Gertsch & Ennik, 1983 – Costa Rica *''Loxosceles rosana, L. rosana'' Gertsch, 1967 – Peru *''Loxosceles rothi, L. rothi'' Gertsch & Ennik, 1983 – Mexico *''Loxosceles rufescens, L. rufescens'' (Dufour, 1820) (Type species, type) – Southern Europe, northern Africa to Iran. Introduced to USA, Mexico, Macaronesia, South Africa, India, China, Japan, Korea, Laos, Thailand, Australia, Hawaii *''Loxosceles rufipes, L. rufipes'' (Lucas, 1834) – Guatemala, Panama, Colombia. Introduced to West Africa *''Loxosceles russelli, L. russelli'' Gertsch & Ennik, 1983 – USA *''Loxosceles sabina, L. sabina'' Gertsch & Ennik, 1983 – USA *''Loxosceles sansebastianensis, L. sansebastianensis'' González-Sponga, 2010 – Venezuela *''Loxosceles seri, L. seri'' Gertsch & Ennik, 1983 – Mexico *''Loxosceles similis, L. similis'' Moenkhaus, 1898 – Brazil *''Loxosceles simillima, L. simillima'' Lawrence, 1927 – Southern Africa *''Loxosceles smithi, L. smithi'' Simon, 1897 – Ethiopia, Malawi, Kenya, Tanzania *''Loxosceles sonora, L. sonora'' Gertsch & Ennik, 1983 – Mexico *''Loxosceles spadicea, L. spadicea'' Simon, 1907 – Peru, Bolivia, Argentina *''Loxosceles speluncarum, L. speluncarum'' Simon, 1893 – South Africa *''Loxosceles spinulosa, L. spinulosa'' Purcell, 1904 – South Africa *''Loxosceles surca, L. surca'' Gertsch, 1967 – Peru, Chile *''Loxosceles taeniopalpis, L. taeniopalpis'' Simon, 1907 – Ecuador *''Loxosceles taino, L. taino'' Gertsch & Ennik, 1983 – Bahama Is., Jamaica, Hispaniola *''Loxosceles tazarte, L. tazarte'' Planas & Ribera, 2015 – Canary Is. *''Loxosceles tehuana, L. tehuana'' Gertsch, 1958 – Mexico *''Loxosceles tenango, L. tenango'' Gertsch, 1973 – Mexico *''Loxosceles tenochtitlan, L. tenochtitlan'' Valdez-Mondragón, 2019 – Mexico *''Loxosceles teresa, L. teresa'' Gertsch & Ennik, 1983 – Mexico *''Loxosceles tibicena, L. tibicena'' Planas & Ribera, 2015 – Canary Is. *''Loxosceles tlacolula, L. tlacolula'' Gertsch & Ennik, 1983 – Mexico *''Loxosceles tolantongo, L. tolantongo'' Navarro-Rodríguez & Valdez-Mondragón, 2020 - Mexico *''Loxosceles troglobia, L. troglobia'' Souza & Ferreira, 2018 – Brazil *''Loxosceles turanensis, L. turanensis'' Zamani et al., 2020 – southern Turkmenistan and eastern Iran *''Loxosceles valdosa, L. valdosa'' Gertsch, 1973 – Mexico *''Loxosceles vallenar, L. vallenar'' Brescovit, Taucare-Ríos, Magalhaes & Santos, 2017 – Chile *''Loxosceles variegata, L. variegata'' Simon, 1897 – Paraguay *''Loxosceles vicentei, L. vicentei'' Taucare-Ríos, Brescovit & Villablanca, 2022 - Chile *''Loxosceles virgo, L. virgo'' Gertsch & Ennik, 1983 – Virgin Is. *''Loxosceles vonwredei, L. vonwredei'' Newlands, 1980 – Namibia *''Loxosceles weyrauchi, L. weyrauchi'' Gertsch, 1967 – Peru *''Loxosceles willianilsoni, L. willianilsoni'' Fukushima, de Andrade & Bertani, 2017 – Brazil *''Loxosceles yucatana, L. yucatana'' Chamberlin & Wilton Ivie, Ivie, 1938 – Mexico, Belize, Guatemala *''Loxosceles zapoteca, L. zapoteca'' Gertsch, 1958 – Mexico

References

External links

Arachnology Home Pages: ''Loxosceles'': Recluse spiders

* [http://spiders.ucr.edu/myth.html Vetter, R. 2003. "Myth of the Brown Recluse: Fact, Fear, and Loathing".]
Pictures of ''L. reclusa'' and wound
(free for noncommercial use) {{DEFAULTSORT:Recluse Spider Sicariidae, Loxosceles Spiders of Africa Spiders of Asia Spiders of North America Spiders of South America de:Sicariidae