The name ‘false widow’ applies to several different species of spider that belong to the genus Steatoda. Only three of these species are commonly found in the UK and Ireland.

The Noble false widow is by far the most notorious of these species and accounts for the majority of recorded bites.

The spider genus Steatoda, in the family Theridiidae, includes about 120 recognised species distributed around the world.

Image showing family, genus and species relationship between false widow and black widow spiders

Distinguishing false widows from black widows

False widow compared to black widow spider

False widow spiders

  • Brown or dark-colored with lighter markings on the abdomen.
  • Various patterns on the body, but not as easily recognizable by markings.
  • Generally lacks distinct red hourglass marking on the abdomen.
  • Legs are generally shorter than a black widow.
  • Abdomen is more rounded.
Black widow compared to false widow spider

Black widow spiders

  • Shiny black appearance.
  • Distinct red or orange hourglass-shaped marking on the underside of the abdomen (Southern black widow).
  • Location of the red or orange markings will vary by species.
  • Legs are generally longer than a false widow.
  • Abdomen is more pointed (tear-drop shaped).

Three false widow species you might see

False widow spiders belong to the genus Steatoda, a group that shares many traits and characteristics with the more infamous black widow spider, which belongs to the genus Latrodectus. Despite being closely related, Steatoda are less harmful to people. The name “false widow” is most often used in reference to three primary species often found near human populations; Steatoda nobilis, Steatoda grossa and Steatoda bipunctata. These species can now be found in Ireland and the United Kingdom, most notably Steatoda nobilis.

False widow’s general appearance

False widow spiders can range in colour from brown to dark purple or black. Their legs are usaully a reddish-orange colour but may be darker or striped depending on the species.

False widows generally have distinctive markings on their abdomens but the marks can vary, be faded, or even missing, especially in the adult females. They have a white or cream coloured band that circles around the front of the abdomen near the head. Other markings will vary by species but are often described as being skull shaped, especially with the Noble false widow (Steatoda nobilis).

Females have a larger and more globular, shiny abdomen while the males are smaller and less rounded, but their markings are usually more clear.

Female Noble false widows average in size from 8.5 to 14mm in total size, while males are 7 to 10mm. The larger specimens can span about the size of a two euro coin.

Male and female baby false widows are indistinguishable.

Several of our native spiders are often mistaken for false widows, you can learn how to distinguish them here.

Male false widow with clear "skull" markings

Adult male Noble false widow spider with distinct markings.

“At the NUI Galway Venom Systems Lab, we have been studying this spider for the past five years and we are finally learning the truth about the false widow story.”

John P. Dunbar, Aiste Vitkauskaite, Sean Rayner and Michel M. Dugon
Venom Systems Lab, NUI Galway
From: RTE Brainstorm

False widow spider webs

The web of the false widow spider is an intricate marvel of engineering designed to provide shelter and to efficiently ensnare its prey. Although not as impressive in symmetry or size as webs spun by the orb-weaving spiders, false widow spiders compensate with their strategic placement and the strength of their silk. While they typically like to create webs in dark and sheltered locations such as crevices, the corners of buildings and garden sheds, they can often be seen all over gardens and street furniture across the UK and Ireland.

The false widow web exhibits a tangled and very irregular pattern with a combination of sticky and non-sticky silk. The sticky silk, known as capture silk, is produced in the centre of the web and serves as the deadly trap for the unsuspecting insects. As prey flies or crawls into the web, they become entangled in the sticky fibres, rendering them immobile.

The false widow, perched nearby, quickly detects the vibrations of its trapped prey and approaches with caution and precision to deliver a potent venomous bite, paralyzing its victim for digestion.

The false widow spider takes great care in maintaining its web, constantly repairing and reinforcing it as needed. Steatoda grossa sometimes prefers to take over another spider’s web instead of expending the time and energy required to build one. Well development webs may have a circular tunnel shape formed near the heart of the web, leading to a more sheltered location.

Examples of false widow spider webs

False widow spider species in Ireland

The three most common false widow spiders in Ireland and Britain are Steatoda nobilis, Steatoda grossa, and Steatoda bipunctata.

Noble false widow spider

Steatoda nobilis

Cupboard spider

Steatoda grossa

Rabbit hutch spider

Steatoda bipunctata

False widow spider lookalikes

Native spiders to Ireland that are often mistaken for false widows.

Lace-weaver

Amaurobius similis

Black lace-weaver

Amaurobius ferox

Missing sector orb weaver

Zygiella x-notata