Steatoda
Encyclopedia
The spider
genus Steatoda, in the family Theridiidae
, includes over 120 recognized species
, distributed around the world (including many cosmopolitan species which are found among human populations worldwide).
These usually dark spiders have in most species a white line around the anterior back, in addition to other lines or spots.
Many spiders of the genus Steatoda are often mistaken for widow spiders (Latrodectus), and are known as false black widows; however Steatoda are significantly less harmful to humans. Steatoda are shaped similarly to widow spiders, with round, bulbous abdomens. However, not all Steatoda species resemble widows – many have distinct coloring, and are significantly smaller than Latrodectus specimens. Some species of Steatoda actually will prey on widows, as well as other spiders which are considered hazardous to humans.
Some members of this genus do have bites which are medically significant in humans (such as S. grossa
and S. nobilis
), however bites by Steatoda species generally do not have any long-lasting effects. The symptoms associated with the bite of several Steatoda species are known in the medical profession as steatodism; and have been described as a less-severe form of latrodectism
(the symptoms associated with a widow spider bite). The redback spider antivenom has been shown to be effective at treating bites from S. grossa, after it was mistakenly administered to a S. grossa bite victim who was erroneously believed to have been bitten by the far more dangerous redback.
In common with other members of the Theridiidae family, the Steatoda spiders construct a tangle web, 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. 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.
Those commonly mistaken for widows include:
Spider
Spiders are air-breathing arthropods that have eight legs, and chelicerae with fangs that inject venom. They are the largest order of arachnids and rank seventh in total species diversity among all other groups of organisms...
genus Steatoda, in the family Theridiidae
Theridiidae
Theridiidae is a large family of spiders, also known as the tangle-web spiders, cobweb spiders and comb-footed spiders. The diverse family includes over 2200 species in over 100 genera) of three-dimensional space-web-builders found throughout the world...
, includes over 120 recognized species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
, distributed around the world (including many cosmopolitan species which are found among human populations worldwide).
These usually dark spiders have in most species a white line around the anterior back, in addition to other lines or spots.
Many spiders of the genus Steatoda are often mistaken for widow spiders (Latrodectus), and are known as false black widows; however Steatoda are significantly less harmful to humans. Steatoda are shaped similarly to widow spiders, with round, bulbous abdomens. However, not all Steatoda species resemble widows – many have distinct coloring, and are significantly smaller than Latrodectus specimens. Some species of Steatoda actually will prey on widows, as well as other spiders which are considered hazardous to humans.
Some members of this genus do have bites which are medically significant in humans (such as S. grossa
Steatoda grossa
Steatoda grossa, commonly known as the cupboard spider, the dark comb-footed spider, the brown house spider , or the false black widow , is a common species of spider in the genus Steatoda...
and S. nobilis
Steatoda nobilis
Steatoda nobilis, commonly known in England as the biting spider or the false widow , is a common species of spider in the genus Steatoda...
), however bites by Steatoda species generally do not have any long-lasting effects. The symptoms associated with the bite of several Steatoda species are known in the medical profession as steatodism; and have been described as a less-severe form of latrodectism
Latrodectism
Latrodectism is the clinical syndrome caused by the neurotoxic venom , that can be injected by the bite of any spider that is a member of the spider genus Latrodectus, in the family Theridiidae....
(the symptoms associated with a widow spider bite). The redback spider antivenom has been shown to be effective at treating bites from S. grossa, after it was mistakenly administered to a S. grossa bite victim who was erroneously believed to have been bitten by the far more dangerous redback.
In common with other members of the Theridiidae family, the Steatoda spiders construct a tangle web, 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. 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.
Species
There are currently over 120 recognized species in Steatoda.- S. borealis. A common species in North America, often mistaken for the black widowBlack widow spiderLatrodectus mactans, the Southern black widow, is a highly venomous species of spider in the genus Latrodectus. They are well known for the distinctive black and red coloring of the female of the species and for the fact that she will occasionally eat her mate after reproduction. The species is...
(despite being smaller and having colored markings on the dorsal side of the abdomen, rather than the ventral side). - S. capensisSteatoda capensisSteatoda capensis is a spider originating from South Africa. Its common names include the black cobweb spider, brown house spider, cupboard spider and due to its similarities to the katipo spider it is commonly known as the false katipo in New Zealand...
, the black cobweb or false katipo spider. Originates in South AfricaSouth AfricaThe Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...
and is found in AustraliaAustraliaAustralia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
and New ZealandNew ZealandNew Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
; in the latter location it is often confused with the katipoKatipoLatrodectus katipo, the katipo, is an endangered species of spider native to New Zealand. A member of the genus Latrodectus, it is related to the Australian redback spider, and the North American black widow spiders. The species is venomous to humans, capable of delivering a comparatively dangerous...
spider. - S. grossaSteatoda grossaSteatoda grossa, commonly known as the cupboard spider, the dark comb-footed spider, the brown house spider , or the false black widow , is a common species of spider in the genus Steatoda...
, often known as the cupboard spider. A dark-colored spider which resembles specimens of Latrodectus, though without the characteristic bright marks found on most widow spiders. This spider is known to occasionally prey on true widows. Bites by S. grossa have been known to produce symptoms similar to (but far less severe than) the bites of true widows. Originally from Europe, but now found worldwide. - S. nobilisSteatoda nobilisSteatoda nobilis, commonly known in England as the biting spider or the false widow , is a common species of spider in the genus Steatoda...
. This spider, a native of the Canary IslandsCanary IslandsThe Canary Islands , also known as the Canaries , is a Spanish archipelago located just off the northwest coast of mainland Africa, 100 km west of the border between Morocco and the Western Sahara. The Canaries are a Spanish autonomous community and an outermost region of the European Union...
, has since been introduced into EnglandEnglandEngland is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...
. It has acquired a bad reputation due to its reportedly-painful bite, including a case of man needing treatment for symptoms of heart seizure. - S. paykulliana, another spider which is often confused with Latrodectus. This one is generally found in the range of Latrodectus tredecimguttatusLatrodectus tredecimguttatusLatrodectus tredecimguttatus, commonly known as the Mediterranean black widow or steppe spider, is a species of widow spiders in the genus Latrodectus. It is commonly found throughout the Mediterranean region, ranging from Spain to southwest and central Asia, hence the name...
and is frequently confused with it. Has a medically significant (but not serious) bite.
Other notable and recognizable species
Other notable and recognizable species in the genus include:- S. bipunctataSteatoda bipunctataSteatoda bipunctata is a species of cob-web spider, of the genus Steatoda, in the family Theridiidae.It is common in North America and Europe and may be found in proximity to human structures, such as basements or sheds. A nickname for this arachnid is the Rabbit Hutch Spider, since rabbit hutches...
. A common house spider in Europe. - S. triangulosa, the triangulate cobweb spiderTriangulate cobweb spiderThe triangulate cobweb spider is a common house spider in the genus Steatoda...
, a common household spider noted for a pattern of triangles on the dorsal side of its abdomen. Not known to bite; found worldwide. - S. hespera, the western bud spider. This species is commonly found in the western United StatesUnited StatesThe United States of America is a federal constitutional republic comprising fifty states and a federal district...
and CanadaCanadaCanada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
, where it is an effective predator of the hobo spiderHobo spiderThe hobo spider is a member of the genus of spiders known colloquially as funnel web spiders, but not to be confused with the Australian funnel-web spider. It is one of a small number of spiders in North America whose bites are generally considered to be medically significant...
. It is often confused (by laypersons) with the black widow, despite being significantly smaller (7 to 8 mm) and having no bright-colored markings. Not known to bite humans, but has a venom which is similar to S. paykulliana (a medically significant spider of this genus).
External links
- The World Spider Catalog
- Washington State University: Steatoda Spiders
- Factsheet on False Black Widow - Woodland Park Zoo, Seattle WA
- Bug Facts: Boreal Cobweb Spider (Steatoda borealis) - Royal Alberta Museum: Invertebrate Zoology
- San Diego Natural History Museum: S. grossa
- S. W. Hahn. "Description of four Steatoda species (Araneae, Theridiidae) found in New Zealand", New Zealand Journal of Zoology, 1994 vol 21 225-238
- American Museum of Natural History: Family Theridiidae