Steatoda Triangulosa – Triangulate Cobweb Spider

The Steatoda triangulosa, commonly called the triangulate cobweb spider is a brown-black spider found throughout the US. It has an iconic triangulate shape on its back.

Steatoda triangulosa Description

The most distinguishing marks on the Steatoda triangulosa are the two darker zigzag markings that run down the abdomen, which form a set of triangular shapes running down the middle between them. They are usually two-toned brown spiders with banded legs.

Steatoda triangulosa triangulate cobweb spider
Can you see the triangulate shapes on its back? Photography by: K. J. Ester – Macomb, Michigan


The Steatoda triangulosa is not a big spider as the body of the adult female reaches only about 1/4 of an inch (6 mm). With the leg spread, it reaches approximately 5/8” (16 mm).


Though some species of the Steatoda family can have medically significant bites, I have not found any evidence of anyone receiving a bite from the S.triangulosa. I have found two different places on-line that says they are harmless, one of them saying they are too small to puncture human skin. Personally, I tend to believe all spiders can bite, but it does sound like the Steatoda triangulosa is on the harmless side.

Scientific Classification of Steatoda triangulosa

  • Kingdom: Animalia
  • Phylum: Arthropoda
  • Subphylum: Chelicerata
  • Class: Arachnida
  • Order: Araneae
  • Infraorder: Araneomorphae
  • Family: Theridiidae
  • Genus: Steatoda
  • Species: Steatoda triangulosa

Distribution of the Triangulate Cobweb Spider in the USA

Steatoda triangulosa triangulate cobweb spider range USA

The Steatoda triangulosa can be found in every state in the United States and Canada. Alabama, Alaska, Arizona, Arkansas, California, Colorado, Connecticut, Delaware, Florida, Georgia, Hawaii, Idaho, Illinois, Indiana, Iowa, Kansas, Kentucky, Louisiana, Maine, Maryland, Massachusetts, Michigan, Minnesota, Mississippi, Missouri, Montana, Nebraska, Nevada, New Hampshire, New Jersey, New Mexico, New York, North Carolina, North Dakota, Ohio, Oklahoma, Oregon, Pennsylvania, Rhode Island, South Carolina, South Dakota, Tennessee, Texas, Utah, Vermont, Virginia, Washington, West Virginia, Wisconsin, Wyoming

Steatoda Triangulosa – Triangulate Cobweb Spider

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