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

Size

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).

Bites

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

25 thoughts on “Steatoda Triangulosa – Triangulate Cobweb Spider

  1. Good day! I had found a tiny, web-residing spider in my room that I have been trying to identify for the past hour but have had no luck. Unless it’s a species that has recently started to migrate to this area, hopefully stating that this is on North Georgia should narrow it down.

  2. I’m my hotel that is just outside FT. Lee VA. Had just caught a fly in its web. I took two videos of it wrapping the fly up. Any idea?

  3. Hi.. this guy or gal was sitting in my bedroom this am. Am hoping it’s a a good spider so I can put it outside to eat insects! Marsville, WA

  4. I’ve looked all over online and I can’t seem to correctly identify the spider. Any help would be appreciated as my cabin is infested with them currently. I live in North Alabama 15 minutes from either Tennessee or Georgia.

  5. I found this underneath of a bicycle, which I pulled from the garage. It was probably the size of a dime. This is near Greenville, SC.

  6. Found in Sonoma (NorCal California)…walking across bathroom floor. No sign of a web. Medium size, maybe 1/2 inch body, with legs 1-1.5 inches. Reddish brown color, with what seemed to be gray or cream markings. Thanks 🙂

    1. Hello Georgina, thanks for getting in touch! This is definitely a male false widow spider (Steatoda sp.). They are close relatives of the black widow and can deliver a painful bite but are not considered medically significant. Male specimen are generally considerably less venomous than females. This fellow is most likely a male triangulate cobweb spider (Steatoda triangulosa): https://usaspiders.com/steatoda-triangulosa-triangulate-cobweb-spider/

      1. What is this? Very tiny: maybe 3/8” and hundreds of them hanging out on a wood crate, NE OK. Many are barely visible they are so small and nearly colorless.

  7. Finally caught this spider in my cupboard..been after it for over a year…it was hiding inside the handle of my pressure cooker with 5 egg sacks..4 were empty, one sack full and there was also a much thinner and more elongated spider skin with them…does this spider that looks just like a black widow except for the yellow zigzag lines kill its make too?

    1. Hello Jennifer, thanks for getting in touch! This is a triangulate cobweb spider (Steatoda triangulosa). They have a similar body shape of black widows as they are in the same spider family. But they are not considered medically significant. The egg sacs are probably of the cobweb spider too. During their lifecycle, they molt several times, so the skin is probably hers too. You can read more about them here: https://usaspiders.com/steatoda-triangulosa-triangulate-cobweb-spider/

  8. ID? Very small. 3/8ths-ish including legs. Found it and it’s hundreds of family mbrs in a wooden palette.

  9. With legs stretched out about size of quarter. Was getting bites 2-4x a night until I was able to kill it, but didnt smash it so I could identify. Bites looked like large mosquito bites with irregular borders. Thought it was hives at first. Would eventually become a deep red dot and itch for a week or so. Thinking it might be a Hobo Spider, but something is off. I live in the East Bay/Northern California. Please help me to identify.

    1. Hello Adam, thanks for getting in touch! This is a cobweb spider (Steatoda sp.), most likely Steatoda triangulosa. Spiders usually only bite to subdue small prey or if the feel threatened. It’s highly unlikely that a spider would bite a human at night, especially several times. We as humans are way to large for them and there would be no point for them to bite humans. The bites are most definitely from another small animal that was feeding on your blood (spiders don’t do that).
      Here is more information about this spider: https://usaspiders.com/steatoda-triangulosa-triangulate-cobweb-spider/

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