Steatoda nobilis

Steatoda nobilis is a spider in the genus Steatoda, known in the United Kingdom as the noble false widow[1][2] and is often referred to as the false widow.[a] As the common name indicates, the spider superficially resembles and is frequently confused for the black widow and other spiders in the genus Latrodectus. S. nobilis has medically significant venom, where in England, it has a reputation as one of the few local spider species that is capable of inflicting a painful bite to humans,[3] with most bites resulting in symptoms similar to a bee or wasp sting.[4]

Steatoda nobilis
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Subphylum: Chelicerata
Class: Arachnida
Order: Araneae
Infraorder: Araneomorphae
Family: Theridiidae
Genus: Steatoda
Species:
S. nobilis
Binomial name
Steatoda nobilis
(Thorell, 1875)

S. nobilis is spotted all year round, both indoors and outdoors in a variety of habitats including cacti, roadside cuttings, and demolished buildings.[5] They prey on both vertebrates and invertebrates using an "attack wrap" strategy where silk is wrapped around the victim.[6]

Steatoda nobilis is native to Madeira and the Canary Islands from where it allegedly spread to Europe,[7] and continued to spread to other parts of the world including the United States, Chile, Columbia and other countries. They are one of the world's most invasive species of spider.[8]

Description

Steatoda nobilis has a brown bulbous abdomen with cream coloured markings that are often likened to the shape of a skull.[9] Their legs are reddish-orange.[10] Both female and male S. nobilis can be distinguished from other spiders of the same genus by their large size and typical colouration. Females range in size from about 9.5 to 14 mm in size, while males are 7 to 11 mm.[1] The largest females can be upto 13.7 mm in size, while the largest males can be 11.66mm in size. The males can be distinguished by their conformation of the palp and by their ventral abdominal markings. The females can be distinguished by their epigyne.[6] The variation in size, shape and markings that have been observed is not thought to be due to location. Spiders found centimeters apart and siblings born from the same egg sac can look very different.[5]

Male and female juvenile spiders are indistinguishable from each other.[5]

Male with swollen pedipalps

Distribution, habitat and ecology

Distribution

The spider is an introduced species across Europe, plus parts of North Africa, and likely spreading. It was found for the first time in 2011 in Cologne, Germany.[11] It is originally from the Canary Islands and Madeira.[12] In England it has been reported mostly in southern counties,[13][14] but its range appears to be expanding northwards.[15] In 2011, the spider was reported as an established invasive species in the USA, in Ventura County, California.[16] In January 2016, it was reported that Steatoda nobilis had been found in Chile, the first time that the species had been recorded in the southern hemisphere.[17][18] Research published in December 2018 showed that it was also established in Colombia and Ecuador.[19]

They are regarded to be one of the world’s most invasive species of spiders.[8] Seaside cities and villages with a temperate climate are especially favorable habitats for this spider.[20]

The first recorded observation of S. Nobilis in England dates back to 1879. The first recorded observation of S. Nobilis in Ecuador was in 2014 at several locations as high as 2800 meters.[20]

Between 1985-2010 there was not high reportings of S. Nobilis anywherer, and scientists consider this to be a typical lag phase that is a phenomenon observed in many invasive species.[21] Afterwards there was a large accelerated spread observed all over the globe.

They are able to establish in urban environments and build large populations in a short time frame.[20]

Habitat

They can be found year round, regardless of the climate, and they can be found both indoors and outdoors.[5] They have been observed in a variety of different places from cacti and agave to roadside cuttings and buildings. They have also been found on telegraph poles, concrete fence posts, and ivy growing on walls.[1] In Ireland they have been observed to be restricted to man-made habitats such as on steel, concrete or timber structures in urbanized area and not commonly found in forests or dunes.[20] In another study done in Ireland, the adult spiders were exclusively only found on steel, concrete or timber structures in urbanized area.[5] In California they have also been observed in urban habitats[22] but recently have been observed to spread into natural habitats.[20]

Juveniles are observed to live in small crevices and holes, which can make their eradication difficult.[20] In Dublin, juveniles have been observed on vegetation and leaves.[5]

In Ireland, they were observed to be captured by common suburban spiders like the cellar spider or the lace-webbed spider.[5]

Population expansion in UK and Ireland
Steatoda nobilis, Hampshire, England

The distribution of Steatoda nobilis is expected to increase northwards in the UK, due to, at least partly, mild winters in recent years. This prediction was reported by Stuart Hine of the Natural History Museum,[23] and is substantiated by the National Recording Scheme.[14]

The spider is reported to be an established species in Ireland.[24] The first recorded sighting of the species occurred in the east of Ireland in Bray, Co. Wicklow in 1997.[25]

Diet

Hunting strategy

Steatoda nobilis uses an effective “attack wrap” strategy to immobilize would-be prey or predators, meaning that they are in close contact to their prey/predator.[6] Prey is captured in typical theridiid fashion, where silk is wrapped around the victim using the spider’s fourth legs. Allowing the spider to bite the victim. Their venom allows them to immobilize their prey by inducing paralysis. S. nobilis have been observed biting insects and spiders which causes a rapid reduction in motor function, most likely due to the release of venom.[1]

Adult diet

S. nobilis can eat both vertebrates and invertebrates. In Ireland, they were observed to eat woodlice.[5] All of S. nobilis’s liquid requirements are observed to come from its prey. In laboratories they seem to thrive without water and in extremely dry conditions.[1] In Ireland they have observed to prey on protected reptile species.[20]

Webs

As with other members of the family Theridiidae, Steatoda nobilis constructs a cobweb which is an irregular tangle of sticky silken fibres. Its 'scaffold web' differs from others of the genus in the exceptional strength of the silk, and in the tubular retreat that is at least partly concealed in a deep crack or hole.[14] They produce three dimensional cob webs. The web is developed slowly, starting as a typical theridiid tangeled web and gradually takes on the characteristic form over several days.[26] They have poor eyesight and depend mostly on vibrations reaching them through their webs to orient themselves to prey or warn them of larger animals that could injure or kill them.

Reproduction and life cycle

Egg laying

Before oviposition, the female produces an irregular, silky brooding chamber that does not have an entrance. They spend about two to ten days in the chamber producing the egg sacs. The egg sacs are spherical or pear-shaped.  When the egg sacs are produced a first layer of loose silk is wrapped around the eggs and then a second layer of denser silk is added. The egg sacs are about 5-12mm in diameter and are suspended by threads inside the brooding chamber. Each egg sac contains 94 eggs on an average but the numbers can range from 34 to 208 eggs.[5]

The spiderlings will emerge from their chorion 18 days after egg production, and remain within the egg sac. After the first molt, the spiderlings will emerge from the egg sack. At this point they are able to capture and consume small live prey.[8]

The period of time between mating, egg-laying and emergence of spiderlings can vary, and is temperature dependent.[8] They are able to build several egg sacs within one season,[5] and in one study they found that one female spider produced four egg sacs within four months

S. nobilis can produce large amounts of offspring for a long period after mating.[6]

Lifespan

The S. nobilis spiders have a high longevity, with a lifespan of up to five years. They have a fast reproductive rate and are cold tolerant with year-round activity.[6]

Adult females are observed to be extraordinarily long-lived and persistent. One adult S. nobilis female was reported to live almost five and a half years in captivity.[20]

Mating

After locating a female’s web, Steatoda nobilis males pluck or tap the web in a rhythmic way with the second pair of legs. This is accompanied brief bursts of abdominal vibrations. While this occurs, the male uses his first pair of legs to search for the female. If the legs make contact with the female, the male will repeatedly jab his palps into the epigyne until the palps are inserted.[8]

Males are able to produce stridulation sounds during courtship, by scraping 10-12 teeth on the abdomen against a file on the rear of the carapace.

Bites to humans and animals

S. nobilis presents a unique risk because of their synanthropic habits, especially in temperate regions, that bring them in close contact to humans. They are considered one of the most dangerous spiders in Western Europe.[6] The mechanical bite from an adult S. nobilis is usually painless. It is the release of venom that causes the intense pain commonly reported.[6] Male bites are less severe than those of females.[18]

Venom composition

Two thirds of the venom is composed of latrodectus-like toxins. Since the toxins are so potent towards the nervous system, they are known to induce neuromuscular paralysis, extreme pain, and occasionally can be responsible for human fatalities. Their venom is mainly composed of peptidase, serine protease, alpha latrotoxin and delta lactroinsectotoxin. Peptidase and serine protease are both pancreatic lipases and chitinases (enzymes) that help with digestion. Alpha-latrotoxin and delta lactroinsectotoxin are toxins. About 49% of the venom is toxins, 15% are enzymes, 18% are proteins with other functions and 18% are proteins with unknown functions.[6]

Venom mechanism

Alpha-latrotoxin works by creating a pore in the neurons and allowing an influx of Ca2+. This triggers an efflux of neurotransmitters, and once all the neurotransmitters leave, the signals between nerve and muscles are blocked. This leads to neuromuscular paralysis.[6] Their venom is fast acting that allow it to subdue both invertebrate and vertebrate prey.[6]

Venom function

The venom of S. nobilis serves two functions: immobilization of prey or predators and the predigestion of prey. This spider is able to efficiently and safely capture prey that are often times much larger or stronger than them via the rapid paralysis/ immobilization tactic. Their venom is fast acting and can subdue both invertebrate and vertebrate prey. The range of enzymes in the venom suggest that the venom also functions to pre-digest the prey. One example is the enzyme Chitinase which can breakdown the exoskeleton (shell) of arthropods.[6]

Signs and symptoms

The symptoms of a bite are typically similar to a bee or wasp sting.[10] The bite of this spider, along with others in the genus Steatoda, can produce a set of symptoms known as steatodism. Symptoms of bites include intense pain radiating from the bite site, along with feverishness or general malaise.[27] Some of the other symptoms observed in humans after envenomation includes prolonged, moderate to intense pain, swelling and erythema.[26] Other symptoms can include piloerection, diaphoresis, facial flushing, feverishness, vasodilation of capillaries localized near the site of the bite.

Secondary bite effects

In December 2020, a study was published by NUI Galway which determined that the noble false widow transmits bacteria which are antibiotic resistant. It carries this bacteria on its chelicerae and the surface of its body. Some of the 12 pathogenic bacterial species isolated include S. epidermis, K. intermedia, and P. putida. This showed that the bacteria were from the spider directly, instead of from opportunistic bacteria that were already present on the skin of bitten humans.[28]

Media reaction

Sensationalised stories about the bite of Steatoda nobilis have featured in UK newspaper articles.[29][30] Stuart Hine from the Natural History Museum, London responded on the naturenet blog, stating, "Of course I also explain the great value of spiders and how rare the event of spider bite in the UK actually is. I also always explain that up to 12 people die from wasp/bee stings in the UK each year and we do not panic so much about wasps and bees – but this never makes it past editing." [23] Steven Falk, an entomologist, cautioned that without "hard evidence", it is difficult to know how many of the bites reported in the media have been caused by false widow spiders.[31] The arrival of Steatoda nobilis in Chile in 2016 led to a similar media reaction.[32]

Alleged incidents
  • In 2006 a Dorchester man spent three days in Dorset County Hospital with symptoms of heart seizure, after suffering a spider bite believed to be caused by Steatoda nobilis.[3]
  • In 2013 a man in Sidcup, Kent was allegedly bitten in his sleep, reporting that his hand had turned black and yellow. His hand remained swollen for five weeks until doctors gave him a course of antibiotics.[33]
  • In October 2013, it was reported that a man from Romford in London had been allegedly bitten by a false widow. He was treated for bacterial infection with antibiotics and needed to have his leg drained of pus.[34]
  • In October 2013, a British school in the Forest of Dean was closed for a day for fumigation as a result of a dense population of Steatoda nobilis on the site.[35]
  • In 2014, a woman from County Durham had her left index finger amputated after contracting the flesh-eating bug necrotising fasciitis following a claimed bite from a false widow spider.[36][37]
  • In October 2014, an Irish man went into cardiac arrest and spent a day in intensive care after being bitten three times by what was claimed as a false widow, on the hip, side and shoulder.[38]
  • In October 2018 four east London schools were closed due to false widow spider infestations.[39]
  • In September 2019, it was reported that a man in Southampton was bitten while he slept, and left "barely able to walk".[40]

Notes

a. ^ The full English name for Steatoda nobilis is "noble false widow". Media coverage usually abbreviates this to "false widow", although Steatoda nobilis is only one of the false widows. Steatoda grossa[41] and Steatoda paykulliana[42] are other examples of false widow spiders.

References
  1. Snazell, R. & Jones, D. (1993). "The theridiid spider Steatoda nobilis (Thorell, 1875) in Britain". Bulletin of the British Arachnological Society. 9 (5): 164–167.
  2. Jones, D. (1993). "The Return of Steatoda nobilis (Thorell)". Newsletter of the British Arachnological Society. 49: 7–8.
  3. David Sapsted (17 November 2006). "Watch out, the black widow's sister is ready to bite you". Daily Telegraph. London.
  4. "False widow spider, Steatoda nobilis". Natural History Museum. Retrieved 11 October 2013.
  5. Dugon, Michel M.; Dunbar, John P.; Afoullouss, Sam; Schulte, Janic; McEvoy, Amanda; English, Michael J.; Hogan, Ruth; Ennis, Collie; Sulpice, Ronan (2017). "Occurrence, reproductive rate and identification of the non-native Noble false widow spider Steatoda nobilis (Thorell, 1875) in Ireland". Biology and Environment: Proceedings of the Royal Irish Academy. 117B (2): 77–89. doi:10.3318/bioe.2017.11. ISSN 0791-7945.
  6. Dunbar, John P.; Fort, Antoine; Redureau, Damien; Sulpice, Ronan; Dugon, Michel M.; Quinton, Loïc (June 2020). "Venomics Approach Reveals a High Proportion of Lactrodectus-Like Toxins in the Venom of the Noble False Widow Spider Steatoda nobilis". Toxins. 12 (6): 402. doi:10.3390/toxins12060402.
  7. Kulczycki, A., Legittimo, C.M., Simeon, E. and Di Pompeo, P. (2012). "New records of Steatoda nobilis (Thorell, 1875) (Araneae, Theridiidae), an introduced species on the Italian mainland and in Sardinia". Bulletin of the British Arachnological Society. 15 (8): 269–272. doi:10.13156/arac.2012.15.1.269. S2CID 84102334.CS1 maint: multiple names: authors list (link)
  8. Snazell, R. (1993). "The theridiid spider Steatoda nobilis (Thorell, 1875) in Britain" (PDF). NeoBiota: 164–167 – via NeoBiota.
  9. Sebastian Salek (24 September 2013). "More sightings of the false widow spider, as Britain's 'most venomous arachnid', with orange legs and white skull markings spotted in Essex". The Independent. London.
  10. "Noble false widow spider marches north in the UK". Natural History Museum. Retrieved 11 October 2013.
  11. "Observation by C Wieczorrek". 15 December 2006. Retrieved 22 November 2012.
  12. "World Distribution Map of S. Nobilis". British Arachnological Society. Sep–Oct 2012. Retrieved 22 Nov 2012.
  13. Harvey, P.R.; Nellist, D.R.; M.G. Telfer, eds. (2002). Provisional Atlas of British spiders (Arachnida, Araneae). 1 &2. Huntingdon: Biological Records Centre.
  14. "Summary for Steatoda nobilis (Araneae)". British Arachnological Society: National Recording Scheme. 2010–2012. Retrieved 22 Nov 2012.
  15. "Biting spider widens its web". BBC News. 2001-09-21.
  16. "European Spider, Steatoda nobilis Theridiidae". University of California, Riverside. Retrieved 11 October 2013.
  17. "Steatoda nobilis (Araneae: Theridiidae) in South America: a new alien species for Chile". 26 January 2016. Retrieved 24 March 2016.
  18. "Primer registro de una mordedura de Steatoda nobilis (Thorell, 1875) (Arachnida: Araneae: Theridiidae) en Chile (First record of a Steatoda nobilis (Thorell, 1875) (Arachnida: Araneae: Theridiidae) bite from Chile)" (in Spanish). 21 March 2016. Retrieved 24 April 2016.
  19. "NUEVOS REGISTROS DE STEATODA NOBILIS (THORELL, 1875) (ARANEAE: THERIDIIDAE) DE SUDAMÉRICA". Retrieved 2020-05-30.
  20. Bauer, Tobias; Feldmeier, Stephan; Krehenwinkel, Henrik; Wieczorrek, Carsten; Reiser, Nils; Breitling, Rainer (2019-11-02). "Steatoda nobilis, a false widow on the rise: a synthesis of past and current distribution trends". NeoBiota. 42: 19–43. doi:10.3897/neobiota.42.31582. ISSN 1314-2488.
  21. osf.io https://osf.io/6gv74/. Retrieved 2020-11-16. Missing or empty |title= (help)
  22. Vetter, Richard S.; Rust, Michael K. (July 2012). "A large European combfoot spider, Steatoda nobilis (Thorell 1875) (Araneae: Theridiidae), newly established in Ventura County, California". The Pan-Pacific Entomologist. 88 (1): 92–97. doi:10.3956/2011-40.1. ISSN 0031-0603.
  23. "The Ranger's Blog: The truth about Steatoda nobilis - is it the UK's most dangerous spider?". 2 May 2007. Retrieved 22 November 2012.
  24. "Poisonous false widow spiders spread across Ireland". Irish Independent. 18 October 2013. Retrieved 18 October 2013.
  25. "False Widow spider: What to do if you find one, how to get rid of them and what to do if you've been bitten". independent. Retrieved 2020-04-14.
  26. Dunbar, John P.; Afoullouss, Sam; Sulpice, Ronan; Dugon, Michel M. (2018-06-03). "Envenomation by the noble false widow spider Steatoda nobilis (Thorell, 1875) – five new cases of steatodism from Ireland and Great Britain". Clinical Toxicology. 56 (6): 433–435. doi:10.1080/15563650.2017.1393084. ISSN 1556-3650. PMID 29069933.
  27. Warrell, D.A., Shaheen, J., Hillyard, P. D. & D. Jones (1991). "Neurotoxic envenoming by an immigrant spider (Steatoda nobilis) in southern England". Toxicon. 29 (10): 1263–1265. doi:10.1016/0041-0101(91)90198-Z. PMID 1801319.CS1 maint: multiple names: authors list (link)
  28. "Study Finds Noble False Widow Spiders Bite Can Transmit Harmful Antibiotic-Resistant Bacteria to Humans". NUI Galway. 2 December 2020. Retrieved 3 December 2020.
  29. Williams, Rob (17 October 2013). "Killer spiders on the loose! (or not really) - a guide to the really quite harmless false widow". The Independent. London. Retrieved 17 October 2013.
  30. "False widow spiders aren't out to get us – and their bite isn't dangerous". The Guardian. 17 October 2013. Retrieved 17 October 2013.
  31. "False widow spider bites footballer Steve Harris". BBC News. 10 October 2013. Retrieved 10 October 2013.
  32. "Faúndez, E.I, & Téllez, F. (2016). Considerations about Steatoda nobilis (Thorell, 1875) in Chile. Biodiversity And Natural History, 2(1), 13-15" (in Spanish). 22 June 2016. Retrieved 27 June 2016.
  33. Salek, Sebastian (19 September 2013). "Bites reported across London and Kent as south east sees influx of Britain's most poisonous spider". The Independent. Retrieved 4 October 2013.
  34. "Collier Row dad faced losing leg after false widow spider bite". Romford Recorder. 11 October 2013.
  35. "False widow spider outbreak shuts Forest of Dean school". BBC News. 22 October 2013.
  36. "Woman 'loses finger after being bitten by a spider'". Sunderland Echo. 29 September 2014.
  37. "County Durham mum loses finger after spider bite causes flesh-eating bug". ChronicleLive. 29 September 2014.
  38. "A young father-of-one has told how he almost died when he was attacked and bitten by a lethal false widow spider". Irish Independent. 1 October 2014.
  39. "False widow spider infestations close four east London schools". Guardian. 4 October 2018.
  40. "Lewis, 26, suffers severe bites from spider infestation at Canberra Towers". Southern Daily Echo. 2019-09-10. Retrieved 2019-09-11.
  41. The truth about false widow spiders Natural History Museum.
  42. False widow spider, Steatoda paykulliana Natural History Museum.
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