boreal combfoot

(Steatoda borealis)

Conservation Status
boreal combfoot
Photo by Alfredo Colon
  IUCN Red List

not listed


NNR - Unranked


not listed


Boreal combfoot is a medium-sized false widow spider. It occurs in the United States from Maine to Montana south to South Carolina and Arizona and in Alaska, and across southern Canada. It is most common in the northern states, and this is the source of the first part of its common name. It is common in Minnesota. It is found on trees under bark, in rock crevices, among stones, under bridges, on fences, on protected areas of sheds and other outbuildings, and in basements.

Females are ¼ (6 to 7 mm) in length and have a ½ to (12 to 15 mm) legspan. Males are smaller, 316 to ¼ (4.7 to 6.0 mm) in length.

The front part of the body (cephalothorax) is flat. The hardened plate (carapace) covering the cephalothorax is orangish-brown, glossy, and covered with short, stiff hairs. The head region is a little higher than the thoracic region and is narrow, about one-third as wide as the thoracic region. The thoracic region is thick and hard. There is no transverse furrow. There are four pairs of eyes arranged in what appears to be two more or less parallel rows. The first row of four eyes, consisting of the anterior median eyes (AME) and anterior lateral eyes (ALE), is curved backward. The second row, consisting of the posterior median eyes (PME) and posterior lateral eyes (PLE), is straight. The AME are are much larger than ALE and are dark. All of the other eyes are pale. On each side the ALE and PLE are touching. The median ocular area (MOA), the area defined by the middle four eyes, is longer than wide and slightly wider in front than behind. The jaws (chelicerae) have no teeth. On the underside of the cephalothorax the large central plate (sternum) is pointed at the rear.

The abdomen is oval, rounded in the back, and slightly flattened in the rear. The upper surface is dark chocolate brown, smooth, shiny, and covered with scattered, fine, barely visible hairs. There are four small depressions on the front half, often with a small white or dot in the center of each. There is usually a pale longitudinal stripe extending from the front margin to the middle, and a pale stripe on the lateral margins on the front half of the abdomen. This is often referred to as the “T mark”. The central stripe is often broken into several spots. The front of the abdomen on both sexes is ridged and rough, forming a stridulating organ. When rubbed against the carapace it produces a shrill sound. The underside of the abdomen is mostly pale, dark in the middle, and dark on the rear and lateral margins. There is a pale ring around the spinnerets.

The legs are stout, moderately long, and brown or light brown with darker brown rings. They are not spiny but are densely covered with hairs. The first pair of legs is the longest, the third pair is the shortest, and the fourth pair is only slightly shorter than the first pair. There is a row of 6 to 10 slightly curved bristles (“comb”) on the last segment (tarsus) of each hind leg. This is the feature that gives the family one of its common names. There are three claws at the end of each tarsus, but these are not visible to the naked eye.




Female Body Length: ¼ (6 to 7 mm)

Male Body Length: 316 to ¼ (4.7 to 6.0 mm)

Legspan: ½ to (12 to 15 mm)




The web is irregular, sheet-like, and sometimes flat, but is often crowded in a corner and not appearing sheet-like. It is supported by threads extending in all directions.


Similar Species


Trees, rocks, stones, bridges, fences, outbuildings, and basements.










Life Cycle








Distribution Map



29, 30.





  Class Arachnida (arachnids)  


Araneae (spiders)  


Araneomorphae (typical spiders)  
  Infraorder Entelegynae (entelegyne spiders)  
  Superfamily Araneoidea (araneoid spiders)  


Theridiidae (cobweb spiders)  


Steatoda (false widow spiders)  





Common Names


boreal cobweb weaver

boreal combfoot

northern cobweb weaver










The hard, upper (dorsal), shell-like covering (exoskeleton) of the body or at least the thorax of many arthropods and of turtles and tortoises. On crustaceans, it covers the cephalothorax. On spiders, the top of the cephalothorax made from a series of fused sclerites.



The front part of a spider’s body, composed of the head region and the thoracic area fused together. Eyes, legs, and antennae are attached to this part.



The pair of stout mouthparts, corresponding to jaws, in arachnids and other arthropods in the subphylum Chelicerata.



The large central plate on the underside of the cephalothorax of a spider.



On insects, the last two to five subdivisions of the leg, attached to the tibia; the foot. On spiders, the last segment of the leg. Plural: tarsi.





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Alfredo Colon

    boreal combfoot      





Steatoda borealis
Andrew Hoffman
  Steatoda borealis  



Visitor Videos

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Other Videos
  The great Northern Cobweb Weaver, Steatoda borealis
PZ Myers

Jun 2, 2021

I'm going to tell you all about one of our Minnesota native spiders, Steatoda borealis, and how I'm trying to raise them in the lab.

  Northern Cobweb Weaver (Theridiidae: Steatoda borealis) Female
Carl Barrentine

May 22, 2012

A harmless 'black widow' look-a-like. Photographed at Grand Forks, North Dakota (22 May 2012).

  False widow, Steatoda nobilis bite.
Tone Killick

Nov 4, 2019

This may not seem ethical and I know some will not be happy with this but then I am not happy with the constant barrage of unjustifiable tabloid articles that vilify this species on a daily basis which perpetuates the deadly spider myth thus resulting in the deaths of countless Steatoda nobilis and other mistaken species. Yes, the spider would have been stressed and agitated but it shows also that in this condition the spider still did not bite. Rest assured she was relocated back to her web safe and sound. The reason behind this vid is that I have seen many posts of people claiming to have been bitten by Steatoda nobilis simply by brushing past their webs which I think is pretty nigh on impossible and for a while I have been mulling over the idea of subjecting myself to a Steatoda nobilis bite or should I say, show their reluctance to bite. Today decided to put this to the test. Forgive the jumpy narrative but it seems scaremongering tabloids do have an effect even on those who clearly disbelieve their nonsense 😏

  Noble False Widow Spider (Steatoda nobilis) - Brighton, December 2020
Phil Booker

Dec 16, 2020

UPDATE: I'm no expert on spiders but it appears this video is showing some unexpected behaviour, with a number of more informed people than I telling me they had not before witnessed 'bridging behaviour' from a Noble False Widow. Bridging is a technique used by spiders for web construction. The spider produces a silk thread that is carried by the wind and becomes attached to an object, forming a bridge. Here for example the Spider eventually managed to bridge the gap between two Ivy flower heads, on a blustery day too.


Originally native on the island of Madiera and the Canary Islands the Noble False Widow, spread through Europe before it was first spotted in the UK in 1879, where it was previously restricted to southern counties, but now appears to be expanding north, no doubt encouraged by the recent milder winters.

I think its fair to say this is probably the spider I have the largest number of, in and around my house, although one usually sees them during the hours of darkness, not in full daylight view building a web on the highest part of the Ivy.

Its name refers to an alleged resemblance to the Black Widow spider which has a venom over 1,000 times more venomous and is not found in the UK (thankfully). With the name comes a reputation for venomous bites, which certain parts of the media seem to take delight in reinforcing. In truth, bites on humans are rare, although that's no recommendation to go picking one up

There are a number of Steatoda species found in Britain, with nobilis being the largest.

Despite its reputation as the UKs most fearsome spider, the very late-flying Common wasp (Vespula vulgaris) which appears out of the blue near the start of this video doesn't appear to have heard the rumour. Neither in fact has our Spider friend

I fully expected the Wasp to be pounced upon, whereas if anything, our Noble widow appears to do a bit of a runner, at first.

The specimen in this video is a male. The female is considerably bigger She can have a body length of up to 15mm and a leg span of nearly 35mm. The female spider also lives longer than the male; up to 3 years compared to 1 year for the male.


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Visitor Sightings

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  Alfredo Colon
8/16 to 8/18/2019

Location: Slinger, Wisconsin

boreal combfoot  






Created: 1/24/2022

Last Updated:

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