Steatoda Grossa – False Black Widow Spider

The Steatoda grossa, commonly called the false black widow spider or cupboard spider can be found throughout the United States. It is from the family of Theridiidae, the same as the black widow spiders. They build similar webs and have a similar body shape and color as black widows. Hence, their common name false widow. The bite of a false black widow spider is considerably less severe than a real widow’s bite. However, it is one of the few species that are considered medically significant as the bite can cause severe pain. It is from the same genus as the Steatoda triangulosa and the Steatoda bipunctada.

Steatoda grossa is an imported species that originated in Europe. In the United States, it occurs most often along the East Coast as well as in California. But over the last years, it has spread throughout the United States and can be found in every state.

False Black Widow Spider Description

Steatoda grossa has a similar body shape as the real widow spiders of the genus Latrodectus. The abdomen of the female is large, bulbous and round. Their body color ranges from light brown to purplish to deep black. Especially older female specimen are often confused with black widows. If you can catch a glimpse at the underside of the abdomen and you cannot see a red hourglass shape, it is not a real black widow and you are most likely dealing with a false widow. If the general color of the body is more like a dark purple instead of black, it is also an indication for a false widow.

Female false widow steatoda grossa with brown body
A female Steatoda grossa with a brown abdomen. With this coloration, it is easy to distinguish this species from the black widow. Photo: Nikk

Size

The female false black widow normally has a body size of 0.25-0.40 inches (6-10 mm). Their total leg span is about 1 inch (25 mm). The male is slightly smaller and has an oblong abdomen.

Male cupboard spider steatoda grossa brown orange body
The male false widow spider looks very different from the female and has a long abdomen. Photo: Flickr

Web

Steatoda spiders are part of the cobweb spider family. They don’t spin beautiful round webs like orb weavers in the open. Their webs are tangled and irregular with unorganized strands of sticky silk. They often build their webs in corners of buildings or other crevasses and spend most of their time inside their web waiting for prey to get tangled up in it. This has also earned them their other common name Cupboard Spider.

Interestingly enough, one of the preferred prey are real black widow spiders as well as other small creatures.

False black widow in its web cobweb spider black steatoda grossa
The messy and irregular web of a false black widow. In this picture, you can see the missing red hourglass on the lower side of the abdomen that would make this spider a real black widow. Photo: Flickr

False Widow Bite

The Steatoda grossa is, like the other species from its genera, a timid spider. Whenever a human or a large animal gets close to their web, they will be able to feel the vibrations and hide away from the danger. They only bite if they feel immediately attacked or trapped. Never touch a cobweb in a corner with your hands, use a broom or another tool to avoid being bitten in the hand.

The bite of a false widow is not considered medically significant. That means that the bite itself can be painful and cause blistering in the area around the bite. In addition, the bite may lead to a general discomfort and even fever for several days. The bite does not cause any long-term effects and is not as severe as the bite of a real black widow.

Scientific Classification of Steatoda grossa

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

Other common names

Steatoda grossa is known under the following common names: False widow spider, false black widow spider, cupboard spider, brown house spider and dark comb-footed spider.

False Widow Spider Range in the USA

Steatoda Grossa False Black Widow Range USA

The Steatoda grossa can be found throughout the United States in the following states: 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 Grossa – False Black Widow Spider

25 thoughts on “Steatoda Grossa – False Black Widow Spider

  1. This one has banded legs with bright orange banding closer to the body. Keeps a web which catches insects. Possibly a rabbit hutch spider?

    Please identify this spider.

    Thanks,
    Steve
    Norhern Kentucky

    1. Hi Doug, wow, that was an unfortunate typo! Thanks for pointing that out. It has now been corrected. The bite of the false widow is not medically significant.

  2. Hi there – I saw this beautiful spider in the channeled scablands (sagebrush desert) of eastern Washington state. It’s <1/2 inch and had a messy web in a small depression amidst dirt, grasses, and rocks. I didn't have any luck identifying it with your sorting tool. Hoping someone might know what it is. Thanks, Maureen

  3. Big abdomen about the size of a marble, very slick and glossy, long back legs, long front legs, medium and short middle legs. Very deep black color, legs have patches of brown in some areas, very strange markings on the abdomen, reminds me of a cyclops with a big smile towards the front. I’m curious what it is?

    20210605_024222

    1. Hello Paul, thanks for reaching out! The shape of the abdomen and legs indicates that this is some type of female cobweb spider of the family Theridiiae. Since there is no red hourglass shape on the underside, it is not a black widow but a spider of the genus Steatoda (false widows). Assuming that the spider was found somewhere in the United States, it is most likely Steatoda grossa: https://usaspiders.com/steatoda-grossa-false-widow-spider/

  4. Steatoda grossa typically builds webs under boards, under debris and in secluded areas like water meter housing or under furniture. It would be highly unusual for a Steatoda to be building a web out in the open or under the eves of a house. This image is likely an araneid (orb weaver).

  5. I found this in my mailbox. I did not roll it over to see if it had the red hour glass on its abdomen. But it had the body shape I associate with the black widow. Any idea what it is. I live north of Detroit.

    1. Hello Marc, thanks for getting in touch! This is a false black widow spider of the genus Steatoda. They have a similar body shape as black widows but are not medically significant. Black widows are entirely black and Steatoda sp. spiders usually also have some brown or purple colors like your spider does. So there is no need to turn them around. My best guess is that this is a Steatoda grossa: https://usaspiders.com/steatoda-grossa-false-widow-spider/

  6. Found sitting on a pile of light pink eggs inside my hose storage box, in Suamico Wisconsin. I’ve never seen eggs this color! Relatively small/medium spider, dark brown color with very vaguely reddish stripe down abdomen.

    1. Hello Kate, thanks for getting in touch! This is definitely some species of cobweb spider (Theridiiae). Judging from the picture, I would say that this is a false widow spider (Steatoda grossa): https://usaspiders.com/steatoda-grossa-false-widow-spider/
      If the spider has a red hourglass marking on the bottom of its abdomen, it could be a northern black widow (Latrodectus variolus): https://usaspiders.com/latrodectus-variolus-northern-black-widow/
      I’d recommend handling it with care but the presence of brown color on its body suggests that it is a false black widow which is not medically significant.

  7. I live in CA and found this spider outdoors right above my garage door. I’m wondering whether to worry about it or not. Thanks.

    1. Hello Belinda, thanks for getting in touch! Can you tell me where you found the spiders (City, US State)? That will help with the identification. Thanks!

        1. Thanks for that information. The two spiders are definitely a male and a female Steatoda spider. The larger darker spider is the female. The smaller spider is the male.
          Unfortunately, it is hard to tell what species they are exactly without seeing the upper side of their bodies (and even then it can be hard). Steatoda spiders are close relatives of the black widow but they are not medically significant. Here is an overview of some common Steatoda spiders: https://usaspiders.com/theridiidae/steatoda/

  8. Please identify these spiders. They are on same web. Here is the 2nd spider. It is much smaller, 1/3rd of size.
    Thank you, Belinda

  9. Found this scary looking little lady in the corner of my office in Vermont. There was no red marking, so my guess is Steatoda Grossa. Very interesting looking creature!

  10. i found this spider in los angeles california. it was fr crawling on the side of my face. i’d like to know if i could’ve died, thanks

    1. Hello Angel, thanks for getting in touch! To answer your last question first: dying from a spider bite is extremely unlikely. Spider bites generally only lead to death for people with preconditions or very strong allergies. In fact, around ten times more people in the U.S. die from bee or wasp bites than from spider bites (40 vs. 4 people per year on average).
      Having said that, this is not one of the medically significant spiders found in the U.S. This is a male false widow, or cupboard, spider. They are related to black widows but not nearly as venomous, especially not the male. The marking on the back indicates that this might be Steatoda grossa: https://usaspiders.com/steatoda-grossa-false-widow-spider/

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