Female Noble false widow spider in web

The Noble false widows

The false widow spiders (Steatoda) form a group of species that, because of their general resemblance to the much more notorious black widow spiders (Latrodectus), can cause concern when found in Britain and Ireland.

Steatoda nobilis is a spider in the genus Steatoda, known in the UK and Ireland as the Noble false widow. It is often referred to as just the false widow, although “false widow” is a more general term applied to a wider group of species with this resemblance. This group includes two other species of the genus Steatoda that are less commonly found in Ireland; Steatoda grossa and Steadoda bipunctata.

Steatoda nobilis is native to Madeira and the Canary Islands from where it is thought to have spread to Europe, and continued to spread to other parts of the world. They are considered to be one of the world’s most invasive species of spider.

The first recorded observation of Steatoda nobilis in England dates back to 1879, while the first recording siting in Ireland was in Bray in the 1990s.

Steatoda nobilis is spotted all year round, both indoors and outdoors in a variety of habitats including cacti, roadside cuttings, and demolished buildings. They have also been found on telegraph poles, concrete fence posts, and ivy growing on walls.

Noble false widow size and appearance

Female Noble False Widow spider size
[Image by Stu’s Images licensed under CC BY-SA 4.0]
Female Steatoda nobilis – Noble false widow spider
Size: 8.5 – 14 mm
Male Noble False Widow spider size
[Image by Alvesgaspar licensed under CC BY-SA 3.0]
Male Steatoda nobilis – Noble false widow spider
Size: 7-10 mm
In female Noble false widows, the distinctive pattern on the abdomen can sometimes be faded or missing. The female’s abdomen is larger and more globular than the male’s. This is common to all false widow species.  

They are always larger than Steatoda bipunctata and usually larger than Steatoda grossa. Their abdomen pattern is often described as ‘skull-shaped’ but is more like a pentagon – it is clearer in males and dimmer or sometimes absent in females. Their legs are uniformly red to brown.

Steatoda nobilis has a brown bulbous abdomen with cream coloured markings that are often likened to the shape of a skull. Their legs are reddish-orange. Both female and male Steatoda nobilis can be distinguished from other spiders of the same genus by their large size and typical colouration. Females range in size from about 9.5 to 14mm in size, about the size of a two euro coin. Males are between 7 to 11mm large.

Male and female juvenile spiders are indistinguishable from each other. Juveniles are observed living in small crevices and holes, which can make their eradication difficult. In Dublin, juveniles have been observed on vegetation and leaves.

Image of a female noble false widow spider size compared to 2 euro coin

Other false widow spiders in Ireland and the UK

There are three species of false widow spiders that can now be found in Ireland and have become widespread throughout the country; (Steatoda nobilis, Steatoda grossa, Steatoda bipunctata).

Cupboard spider

Steatoda grossa

Rabbit hutch spider

Steatoda bipunctata

False widow spider fun facts

False widow spider Ireland lifespan

Years average lifespan

False widow spider poisonous venom

%

As potent as the black widow

False widow spider reproduction rate in Ireland

Offspring per year

False widow bites in Irish homes

%

Of bites occur in beds & clothing

Gathered from data recently published by the Venom Systems Laboratories at NUI Galway.

“Drop for drop, the venom of the Noble false widow is far more potent than any of the native spiders we have assessed and has superior prey capture and predator avoidance strategies.”

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

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

False widow spider in Ireland stories

False widow spider in my pajamas!

False widow spider in my pajamas!

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False widow spider in my house

False widow spider in my house

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Baby false widow spider bite?

Baby false widow spider bite?

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