Steatoda nobilis

Taxobox
name = "Steatoda nobilis"

---

image_caption =
image_width = 250px
regnum = Animalia
phylum = Arthropoda
classis = Arachnida
ordo = Araneae
familia = Theridiidae
genus = "Steatoda"
species = "S. nobilis"
binomial = "Steatoda nobilis"
binomial_authority = (Thorell, 1875)
range_

---

range_map_width = 250px

"Steatoda nobilis", commonly known in England as the biting spider or the false black widow (though several other species are known by the latter name), is a common species of spider in the genus Steatoda. As one of this spider's common name indicates, the spider superficially resembles, and is frequently confused for, the black widow and other venomous spiders in the genus Latrodectus. The spider is native to the Canary Islands but arrived in England in around 1870 through bananas sent to Torquay.cite news
author=David Sapsted|title=Watch out, the black widow's sister is ready to bite you"|work=Daily Telegraph|date=2006-11-17|url=http://www.telegraph.co.uk/news/main.jhtml?xml=/news/2006/11/17/nspider17.xml] In England it has a reputation as one of the few local spider species which is capable of inflicting a painful bite to humans - although this is a comparatively rare occurrence.

Description

Like true widow spiders, "S. nobilis" has a round, bulbous, over-sized abdomen, which is darkly colored. Females typically have pale marble like markings on the dorsal side of the abdomen, with a cream-coloured band and range in size from 7mm to 14mm. Males tend to have smaller more elongated abdomens, with pale brown legs and dark brown, less patterned markings. When a mature male is ready to mate you can see his pedipalps (the mouth feelers) expand into carrot shaped balloons to accommodate a sperm covered silk sheet, ready for mating.Males of this genus are able to produce sounds during courtship by scraping teeth on the abdomen against a file on the rear of the carapace.

Habitat and range

In common with other members of the "Theridiidae" family, "S. nobilis" constructs a cobweb, i.e., an irregular tangle of sticky silken fibers. As with other web-weavers, these spiders have very 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.

Distribution

The spider is found in the Canary Islands, in England around Hampshire, Isle of Wight, Devon and Cornwall, Dorset and Essex [cite web | title = Biting spider widens its web | publisher = BBC News | date =2001-09-21 | url = http://news.bbc.co.uk/1/hi/uk/1555039.stm] , and in Madeira; it has also been observed in parts of continental Europe and Africa. [http://www.britishspiders.org.uk/html/bas.php?page=world&taxon_key=NBNSYS0000039460 British Arachnological Society: World Distribution Map of "S. Nobilis"] .

Population growth in UK

As with many animals extending their range from the continent, the distribution of "S. nobilis" is expected to increase northwards in the UK, due at least partly to climate change. The False Widow spider first arrived in banana shipments from the Canary Islands in around 1870. [Source: ITN News 05th May 2007]

This prediction was reported by Stuart Hine of the Natural History Museum. The spider and alarming stories about it regularly feature in newspaper articles. Hine 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." [ [http://naturenet.net/blogs/index.php/2007/05/02/steatoda#c792 The Ranger's Blog: The truth about Steatoda nobilis - is it the UK's most dangerous spider?] ]

Medical significance

They are not aggressive, and most injuries to humans are due to defensive bites delivered when a spider gets unintentionally squeezed or pinched somehow. It is possible that some bites may result when a spider mistakes a finger thrust into its web for its normal prey, but ordinarily intrusion by any large creature will cause these spiders to flee.

The bite of "S. nobilis" is known to be medically significant in humans, however without any long-lasting effects. 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. [cite journal |quotes=no |doi=10.1016/0041-0101(91)90198-Z |title=Neurotoxic envenoming by an immigrant spider (Steatoda nobilis) in southern England |author=D. A. Warrell, J. Shaheen, P. D. Hillyard & D. Jones |url=http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=1801319&dopt=Abstract |journal=Toxicon |year=1991 |volume=29 |issue=10 |pages=1263–1265] In 2006 a Dorchester man spent three days in Dorchester County Hospital with symptoms of heart seizure, after suffering a spider bite believed to be caused by "S. nobilis". (A spider was observed in the act of biting the man; however it was not captured and positively identified by an expert).

The bite of "S. nobilis", like other "Steatoda" spiders is far less dangerous to humans than that of true black widows.

References

External links

* [http://research.amnh.org/entomology/spiders/catalog/THERIDIIDAE.html World Spider Catalog: Family "Theridiidae"]
* [http://uksafari.com/falsewidows.htm UKSafari.com: False widow spiders]
* [http://homepage.ntlworld.com/ray.hamblett1/nature/spiders.steatoda.html Steatoda nobilis images]
* [http://www.patient.co.uk/showdoc/40002378/ PatientPlus: Spider bites]