Steatoda nobilis

Species of spider

Steatoda nobilis is a spider in the genus Steatoda, known in the United Kingdom as the noble false widow, as it superficially resembles and is frequently mistaken for the black widow and other spiders in the genus Latrodectus. It is often referred to as the false widow, although "false widow" is a more general term applied to a wider group of species with this resemblance. Some bites may cause more significant harm, partly due to pathogenic bacteria from the spiders. and continued to spread to other parts of the world including the United States, Chile and Colombia. They are considered to be one of the world's most invasive species of spider. Their legs are reddish orange. Both female and male S. 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 14 mm in size, while males are 7 to 11 mm. The variation in size, shape and markings that have been observed is not thought to be due to location. Spiders found centimetres apart and siblings born from the same egg sac can look very different. Male and female juvenile spiders are indistinguishable from each other. It is originally from the Canary Islands and Madeira. In England it has been reported mostly in southern counties, but its range was reported to be expanding northwards in the 21st century. In 2011, the spider was reported as an established invasive species in the USA, in Ventura County, California. In January 2016, it was reported that Steatoda nobilis had been found in Chile, the first time that the species had been recorded in the southern hemisphere. Research published in December 2018 showed that it was also established in Colombia and Ecuador. It is considered to be one of the world's most invasive species of spider. Seaside cities and villages with a temperate climate are especially favourable habitats for S. nobilis. The first recorded observation of S. nobilis in England dates back to 1879. The first recorded observation of S. nobilis in Ecuador was in 2014 at several locations as high as 2800 meters. Afterwards there was a large accelerated spread observed all over the globe. They are able to establish in urban environments and build large populations in a short time. but have also been observed to spread into natural habitats. and is substantiated by the National Recording Scheme. The first recorded sighting of the species occurred in the east of Ireland in Bray, Co. Wicklow in 1997.

Steatoda nobilis uses an effective "attack wrap" strategy to immobilise would be prey or predators, meaning that they are in close contact to their prey/predator.

S. nobilis can eat both vertebrates and invertebrates. In Ireland, they were observed to eat woodlice.

As with other members of the family Theridiidae, Steatoda nobilis constructs a cobweb which is an irregular tangle of sticky silken fibres. Its scaffold web differs from others of the genus in the exceptional strength of the silk, and in the tubular retreat that is at least partly concealed in a deep crack or hole. They have poor eyesight and depend mostly on vibrations reaching them through their webs to orient themselves to prey or warn them of larger animals that could injure or kill them.

Before oviposition, the female produces an irregular, silky brooding chamber that does not have an entrance. They spend about two to ten days in the chamber producing the egg sacs. The egg sacs are spherical or pear shaped. When the egg sacs are produced a first layer of loose silk is wrapped around the eggs and then a second layer of denser silk is added. The egg sacs are about 5 12mm in diameter and are suspended by threads inside the brooding chamber. Each egg sac contains 94 eggs on an average but the numbers can range from 34 to 208 eggs.

S. nobilis presents a unique risk because of their synanthropic habits, especially in temperate regions, that bring them in close contact to humans. They are considered one of the most dangerous spiders in western Europe. Other symptoms observed in humans after envenomation include prolonged, moderate to intense pain, swelling, erythema,

Bacterial ulceration, a common risk arising from many minor injuries, may be a complication relating to the bite of Steatoda nobilis. Without proper treatment, this issue may develop into life threatening gangrene or sepsis. In December 2020, a study by scientists at NUI Galway determined that the noble false widow vectors pathogenic bacteria, and that some are antibiotic resistant. It carries bacteria on its chelicerae and the surface of its body. Twelve pathogenic bacterial species were isolated, including Kluyvera intermedia and Pseudomonas putida. This showed that infections may be due to the spider bite directly, rather than opportunistic bacteria present on the skin. In October 2013, following a Steatoda nobilis bite, a man from London was treated for a bacterial infection with antibiotics and required his leg to be drained of pus.

Sensationalised stories about the bite of Steatoda nobilis have featured in UK newspaper articles. Stuart Hine from the Natural History Museum, London responded on the naturenet blog, stating, "Of course I also explain the great value of spiders and how rare the event of spider bite in the UK actually is. I also always explain that up to 12 people die from wasp/bee stings in the UK each year and we do not panic so much about wasps and bees – but this never makes it past editing." The arrival of Steatoda nobilis in Chile in 2016 led to a similar media reaction. While the media response is often exaggerated, Oxford University zoologist Clive Hambler noted that arachnologists should be careful not to automatically dismiss stories of extreme reactions. Instead, he argues that they should collaborate with medical professionals to compile these stories, and examine them with a critical eye to better understand the risks posed by bites. are other examples of false widow spiders.