''Steatoda grossa'', commonly known as the cupboard spider, the dark comb-footed spider, the brown house spider (in Australia), or the false widow or false black widow (though several other species are known by these names), is a common species of

spider Spiders ( order Araneae) are air-breathing arthropods that have eight legs, chelicerae with fangs generally able to inject venom, and spinnerets that extrude silk. They are the largest order of arachnids and rank seventh in total species ...

in the genus '' Steatoda''. It is a cosmopolitan species found in many parts of the world, including North America,

Australasia Australasia is a region that comprises Australia, New Zealand and some neighbouring islands in the Pacific Ocean. The term is used in a number of different contexts, including geopolitically, physiogeographically, philologically, and ecologi ...

, and

Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a subcontinent of Eurasia and it is located entirel ...

. As two of this spider's common names indicate, the spider superficially resembles, and is frequently confused for, the black widow and other venomous spiders in the genus ''

Latrodectus ''Latrodectus'' is a broadly distributed genus of spiders with several species that are commonly known as the true widows. This group is composed of those often loosely called black widow spiders, brown widow spiders, and similar spiders. Howeve ...

''.

Description

Like black widows, the female ''S. grossa'' is 6-10.5 mm in length and dark colored with a round, bulbous abdomen. Typical coloration ranges from purplish brown to black, with light-colored markings. Unlike black widows, redbacks, and other ''Latrodectus'' species, ''S. grossa'' does not have a bright red hourglass pattern or any other bright, distinctive markings. Like many spiders, the male is sometimes smaller but can many times be nearly as long as the females. It measures 4.1-10.0 mm in length and is thinner than the female. The two sexes are colored similarly; however, the sexually mature male almost always has lighter, more reddish-coloured legs than the female. ''S. grossa'' spiders may shed up to six times (instars) before reaching maturity. According to Charles Hogue (Insects of the Los Angeles Basin, 1993), it reportedly preys on black widows. They can go several months without feeding, provided they have access to water. A well-fed female can lay three or more egg sacs each year. Each egg sac typically contains between 40-100 eggs. The mother can often be observed watching her eggs for hours, even days, at a time once the eggs start changing color and grow close to hatching. At normal household temp/humidity, an egg will usually hatch within a month of being laid. The spiderlings are independent from time of hatch. Female ''S. grossa'' spiders can live up to six years; the typical lifespan for the male is 1-1.5 years. Males often die shortly after mating.

Habitat and range

As is common with other members of the family Theridiidae, ''S. grossa'' 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 pose a danger. They are not aggressive, and most injuries to humans are due to defensive bites delivered when a spider gets unintentionally squeezed or pinched. 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. ''S. grossa'' is a

cosmopolitan Cosmopolitan may refer to: Food and drink * Cosmopolitan (cocktail), also known as a "Cosmo" History * Rootless cosmopolitan, a Soviet derogatory epithet during Joseph Stalin's anti-Semitic campaign of 1949–1953 Hotels and resorts * Cosmopoli ...

species and is found in many parts of the world, including all three coasts in North America, in Australia and

New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island count ...

, and in

. A related species, commonly found in North America, is '' Steatoda borealis''. This spider is similar to ''S. grossa'' in shape, but slightly smaller, and is generally found in colder climates. This spider can be identified by colored markings on the dorsal side of its abdomen rather than on the ventral side.

Medical significance

The bite of ''S. grossa'' is known to be medically significant in humans, but minor, without any long-lasting effects. Symptoms of bites include blistering at the site of the bite, muscle spasms, pain, fever, sweating, and/or a general malaise lasting for several days. ''Latrodectus''

antivenom Antivenom, also known as antivenin, venom antiserum, and antivenom immunoglobulin, is a specific treatment for envenomation. It is composed of antibodies and used to treat certain venomous bites and stings. Antivenoms are recommended only if th ...

was shown to be effective in treating bites from ''Steatoda 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.

Footnotes

References

* Levi, H.W. 1957. The spider genera ''Crustulina'' and ''Steatoda'' in North America, Central America, and the West Indies (Araneae, Theridiidae). Bull. Mus. Comp. Zool. 117(3):367-424

External links

San Diego Natural History Museum: S. grossa

GeoSpecies Database University of Wisconsin: S. grossa photo
{{Taxonbar, from=Q311833 Steatoda Spiders of Europe Fauna of the California chaparral and woodlands Spiders described in 1838 Cosmopolitan spiders