The triangulate cobweb spider (scientific name: ''Steatoda triangulosa''; also called the triangulate bud spider) is a common spider in the genus ''

Steatoda The spider genus ''Steatoda'', in the family Theridiidae, includes about 120 recognized species, distributed around the world (including many cosmopolitan species which are found among human populations worldwide). One common name is cupboard spi ...

''. It is well known for the

triangle A triangle is a polygon with three Edge (geometry), edges and three Vertex (geometry), vertices. It is one of the basic shapes in geometry. A triangle with vertices ''A'', ''B'', and ''C'' is denoted \triangle ABC. In Euclidean geometry, an ...

-shaped pattern on the dorsal side of its abdomen.

Description

The adult female triangulate cobweb spider is 3 to 6 mm long (1/8 to 1/4 inch), with a brownish-orange

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 ...

and spindly, yellowish legs, and tiny hairs. The round, bulbous abdomen is creamy in color, with parallel purply-brown zigzag lines running front to back. This distinctive pattern sets it apart from other theridiids in its area. The triangulate cobweb spider is known to prey on many other types of arthropods, ants (including fire ants), other spiders, pillbugs, and ticks. It preys on several other spiders believed to be harmful to humans, including the

brown recluse The brown recluse (''Loxosceles reclusa''), Sicariidae (formerly placed in a family "Loxoscelidae") is a recluse spider with Necrosis, necrotic venom. Similar to those of other recluse spiders, their bites sometimes require medical attention. T ...

. The egg sac of the triangulated cobweb spider is made from loosely woven silk, and is about the same size as the spider itself. Each egg sac contains approximately 30 eggs. Cobweb spiders typically live on windows or in dark areas. They eat for a margin of their day and spend hours developing their web; it does not break if it is woven well. Below or in its web, there may be many dead insects, ranging from stinkbugs to other spiders, and even wasps.

Taxonomy

The species was first described, as ''Aranea triangulosa'', by Charles Walckenaer in 1802. It was transferred to the genus ''

'' by

Tamerlan Thorell Tord Tamerlan Teodor Thorell (3 May 1830 – 22 December 1901) was a Sweden, Swedish arachnologist. Thorell studied spiders with Giacomo Doria at the Museo Civico di Storia Naturale de Genoa. He corresponded with other arachnologists, such as Oc ...

in 1873 (although it had been placed in the genus previously under the

synonym A synonym is a word, morpheme, or phrase that means exactly or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are all ...

''Steatoda venustissima'').

Habitat and range

Similar to other members of the family Theridiidae, ''S. triangulosa'' 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. They are not aggressive. There is one known case of human envenomation. It will not kill a person unless an allergic reaction occurs. ''S. triangulosa'' is a cosmopolitan species, and is found in many parts of the world, including across

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...

, in southern

Russia Russia (, , ), or the Russian Federation, is a List of transcontinental countries, transcontinental country spanning Eastern Europe and North Asia, Northern Asia. It is the List of countries and dependencies by area, largest country in the ...

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

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 Continent#Subcontinents, subcontinent of Eurasia ...

. The spider is believed to be native to Eurasia and introduced elsewhere. This species is primarily a house spider, and builds webs in dark corners of buildings and other man-made structures.

References

External links

Triangulate Household Spider

Steatoda triangulosa Images on BugGuide.net

* https://web.archive.org/web/20060314011949/http://www.puyallup.wsu.edu/plantclinic/resources/pdf/pls107steatodaspider.pdf

* 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
Descriptions of four ''Steatoda'' species found in New Zealand

{{Taxonbar, from=Q1302233 Steatoda Spiders of Europe Spiders of Asia