False Widow Spiders
The term "false widow spider" is used to describe the Steatoda genus of spider, several of which are found in the UK. Each of these spiders bears a visual resemblance to the notorious Black Widow Spiders, to varying degrees. Scientific literature dating back as early as the early 1900's use the term "False Black Widow" to describe the species Steatoda grossa, so it's certainly not a new name invented by the media, as you will often hear other arachnologists incorrectly claim. The term was more suitably reduced to "False Widow" to describe Steatoda nobilis, as this species is never black in colour, although dark brown specimens can be found. The topic was discussed on the Spider ID Facebook Group with excellent research by Martin Bell, who found an early reference to Steatoda grossa as the False Black Widow from the "Bulletin of the New England Museum of Natural History" Volumes 49–88, dating back to 1928.   LINK    LINK 2  
The term "False Widow" is actually highly suited to these spiders. The term recognises the strong visual similarity between some Steatoda species and Latrodectus species of Black Widows, but the term "False Widow" also clarifies that Steatoda species are not members of the far more venomous Latrodectus genus. Even though it's often reported that there are similarities between the extreme, but rare, symptoms of steatodism and the more dangerous, and common, symptoms of latrodectism. In the UK we tend to use the term "False Widow" to describe species of the Steatoda genus, but in N. America, where they have both Steatoda and Latrodectus species, the term "False Black Widow" is still the regularly used common name for Steatoda grossa.

There are six species of false widow spiders that are found in the UK (Steatoda nobilis, Steatoda grossa, Steatoda bipunctata, Steatoda albomaculata, Steatoda triangulosa and Steatoda / Asagena phalerata) and one species (Steatoda paykulliana) that turns up every now and then as an accidental import amidst imported fruit, usually grapes from the Mediterranean. The "reputedly" most venomous species in the UK, and usually the one most often referred to as the False Widow Spider by the media, is the Noble False Widow Spider (Steatoda nobilis). 

Both the Black Widow Spiders (Latrodectus species) and the False Widow Spiders (Steatoda species) belong to the family Theridiidae. Theridiids are often referred to as comb-footed spiders, because of the comb-like rows of curved bristles on the tarsi (feet) of the rear pair of legs. They are also known as cobweb spiders because of their messy and irregular webs. There are around 120 recognised Steatoda species found across the world. See list here: LINK

Noble False Widow Spider   (Steatoda nobilis)

The Noble False Widow Spiders were first recorded in the UK in the 1870's in Torquay and are believed to have been accidentally imported into the UK from the Canary and Madeira Islands, amidst crates of fruit, probably bananas. Although this species has been recorded in the UK for over 140 years it didn't really get a foothold here until around 1980. It is only in the last 10-20 years they have really started to rapidly extend their range and spread further up the country. Steatoda nobilis are now regularly seen in houses and gardens across England. In fact in recent years Steatoda nobilis have now become one of the most common species to be found around homes in the southern half of the country. There is growing concern that nobilis may now be having a negative effect on native species by out-competing and displacing other spiders.

Noble False Widow Spiders are the largest of the false widow species in the UK, with females usually growing to a maximum body-length of around 8-11mm for females, with some specimens reaching 15mm, and a leg-span of 30-35mm. Males reach 7-10mm body-length. They have recently received great interest from the British press and are often reported as being aggressive, dangerous, highly venomous and deadly. Although Steatoda species are capable of delivering a moderately painful bite to humans none of the many specimens that I have ever captured and photographed have ever exhibited any defensive behaviour beyond either playing dead or trying to run away. They can move at a fair pace in short bursts but generally I have found them to be a very docile and slow moving genus of spider.  

LINK 1    LINK 2    LINK 3

Despite being in the UK for around 150 years the Noble False Widow Spider has recently gained a pretty bad, and probably undeserved, reputation, which has been generated by sensationalized stories in the media, such as these examples during 2014:

"False Widow Spider ate my leg!"    "False Widow Spider bites teen in cinema"    "Flesh-eating monsters are still here"    "False Widow Spider ate my foot"   

 "False Widow Spiders are eating Dad alive"    "False Widow Spider bite could kill"    "Killer spiders ate my leg"    "False Widow Spider made my leg explode"

"False Widow Spiders attacked my little girl"    "50 False Widow Spiders invade home"    "Killer Spiders invade Britain"    "False Widow Spiders close school"

These stories are usually highly exaggerated and based on little fact. Rarely has the accused spider been caught for a positive identification, and severe reactions from bites are often a result of infection, either by bacteria from the fangs of the spider itself, but often a secondary infection introduced by the victim scratching the bite with dirty hands. However many scientists are now concerned that the Steatoda nobilis may be of more concern to humans than initially thought, and claimed, by arachnologists. In 2020 Clive Hambler wrote a paper entitled "The 'Noble false widow' spider Steatoda nobilis is an emerging public health and ecological threat.". In this thought-provoking, and lengthy paper Hambler suggests many of his own theories and concerns and on page 29 wrote the following statement aimed at arachnologists, and the B.A.S. in particular:

"I argue that the British Arachnological Society guidance (B.A.S. 2019b, 2019c) on "false widow spiders" (all Steatoda species) needs substantive revision, both in terms of the likelihood of bites and the severity of effects. I disagree that "False widows are sedentary by nature, remaining in their webs". Nor do I agree that "the risk of being bitten by a false widow spider must surely be relatively small". I argue the statement that S. paykulliana "can deliver a painful bite but the venom is quite mild in its effect" should be revised in the light of the experimental studies on mammals (Maretić 1978a). I argue it important not to either overstate or neglect the risk a Steatoda bite poses, and that all bites by Steatoda species should be treated in a similar way until any species-specific variation is identified."

6mm sub-adult male Noble False Widow Spider

Are False Widow Spiders dangerous?

With all the negative attention from the media in recent years are Steatoda nobilis really a danger to humans? There is some debate over whether Steatoda nobilis should be classed as "of no medical significance to humans" or "of minor medical significance to humans". The simple answer is bites from Steatoda nobilis aren't usually of any real concern to humans. False Widow Spider bites are fairly rare. The Noble False Widow Spider is usually a slow moving and fairly docile species that is often very reluctant to bite humans, and will usually only do so if they feel threatened, they're sat on or laid on, or they become trapped between clothes / bed sheets and human skin. The media do a great job of vilifying our wildlife as fear sells newspapers unfortunately. Schools have even been closed down because False Widow Spiders have been found there and parents have overreacted and demanded action be taken. The truth is, if people looked hard enough then these spiders could almost certainly be found in almost every single school in the southern half of the UK. Due to their ability to adapt to various habitats Steatoda nobilis have now become one of the most commonly encountered species of spider to be found around homes in the UK, especially in the SE of England, and yet bites are still fairly rare.

In most cases a bite from Steatoda nobilis is usually considered to be no more painful than that of a bee or wasp sting. Spiders rely on their venom for killing and subduing their prey, and do not want to waste it unnecessarily, so most bites to humans will have little venom injected. The most common symptoms are swelling, and pain at the bite site, which can vary from mild to completely debilitating. More severe symptoms can occasionally occur though and can include severe pain, tremors, itchiness, severe swelling and reddening surrounding the bite area. Very occasionally this can be accompanied by nausea, vertigo, cramps, hypotension, vectored bacterial infections including cellulitis and dermatitis, reduced or elevated blood pressure and possibly even breathing issues. The symptoms vary from one person to the next and depend on the victim's age, general health, the amount of venom injected and their sensitivity to the venom. These more severe symptoms are extremely rare and such incidents are more typically associated with bites to very young children, who tend to be more sensitive to the effects of venom. Most severe cases that include severe swelling and ulceration are caused by infection to the wound. Infections can occur either when introduced directly from bacteria found on the spider's fangs or as a secondary infection introduced by the scratching of the bite area. The type of bacteria found on the fangs of Steatoda nobilis can be highly resistant to antibiotics, so infections caused by a defensive bite could be slow for the patient to overcome. Minor symptoms usually disappear within 3 days. If symptoms persist or are severe then medical assistance should be sought without delay as medical treatment, including antibiotics, may be needed. Excessive swelling or reddening of the bite area could be indications of an infection in which case medical attention should be sought as early treatment with antibiotics will be more effective at fighting any infection. In all cases wounds should be cleaned and a disinfectant applied to reduce the risk of infection. An ice pack may be applied to reduce swelling and pain. Avoid scratching or rubbing the bite area as again this will increase the risk of infection and exaggerate the body's reaction to the envenomation. Antihistamines often help to reduce the body's reaction to spider and insect bites.

It's important to keep things in perspective as there are no confirmed records anywhere in the world of anyone ever dying as a direct result of being bitten by a False Widow Spider. And yet in the UK alone between 2-9 people die every year due to anaphylaxis from bee or wasp stings. Although some people, especially very young children, may be more sensitive to spider venom, there are currently no confirmed records of anaphylactic allergic reactions following a bite from a spider in the UK.

Whilst there is little reason to fear False Widow Spiders, or any spiders found in the UK, if you need to relocate a spider then it's always best to avoid free-handling spiders and catch spiders using the glass and card technique, to avoid accidentally harming the spider or risking harm to yourself.

LINK 1    LINK 2    LINK 3    LINK 4

In In recent years specialist researchers, including Dr John Dunbar, at the Venom Systems and Proteomics Lab at NUI Galway’s School of Natural Sciences have been collecting specimens and data since 2016 for research on Steatoda nobilis. It'll be interesting to see the results of these studies in upcoming years and read how the recent expansion of the range of Steatoda nobilis in the UK is affecting other native species and read the conclusions of the effects on Steatoda nobilis bites to humans.  

LINK    LINK 2    LINK 3    LINK 4    LINK 5    LINK 6

The early results in 2020 of J P Dunbar's analysis of Steatoda nobilis venom has revealed an alarming level of similarities in the make up of the venom of Steatoda nobilis and that of the closely related, and far more dangerous, Latrodectus species of Black Widow spider.  LINK 

Are Steatoda nobilis a danger to native species?
There is growing concern that nobilis may now be having a negative effect on native species by out-competing and displacing other spiders. Steatoda nobilis have a good tolerance to cold weather and can still be active when temperatures are around zero degrees, and too cold for some native species to be active. Steatoda nobilis also live longer than many native species and can often exceed more than five years of age. Steatoda nobilis has been proven to have a more potent venom than any of the native species that have been studied. This species is also proving to be highly adaptable to various habitats. With all these strengths combined Steatoda nobilis is a serious competitor when up against our native spider species and could be a serious threat.

8mm sub-adult female Noble False Widow Spider that still has its striped legs and doesn't yet have the black cephalothorax (upper body / head).

On August 10th 2021 Ben Waddams, wildlife artist and wildlife film presenter, posted images on Facebook of a Noble False Widow Spider feeding on a Pipistrelle Bat. The Steatoda nobilis had caught a small bat pup in its web and was observed feeding on the young bat several nights in a row. Whilst the wrapped bat pup was still hanging in the web a second bat, this time an adult Pipistrelle Bat, was also caught in the web. On the second occasion Ben released the bat from the web unharmed before the spider could inflict any bites. It's not sure whether the spider deliberately built its web by the entrance to the bat roost or whether the bats were caught by chance. This is probably the first record of a spider catching mammalian prey in the UK. 
  LINK    LINK 2


10mm sub-adult female Noble False Widow Spider from my garden fence in SE London, 21st September 2017

The abdominal markings of juvenile specimens can look quite different from those markings found on fully developed adult specimens. 

Steatoda nobilis or Steatoda grossa?
Although variable in appearance adult Steatoda nobilis can usually be distinguished from the similar Steatoda grossa by their larger size, the uniformly orange / brown legs, often with slightly darkened joints and an uninterrupted dorsal pattern. The legs of nobilis are slightly more robust than those of grossa, but this isn't always an obvious feature. Steatoda grossa often have slight stripes on their legs even on mature specimens. The two share different habitats too with Steatoda grossa preferring much darker habitats to nobilis. Both sexes of Steatoda nobilis usually have a pale crescent on the front of their abdomen, but this light band does not extend as far around the abdomen as it does with Steatoda nobilis. On darker specimens of Steatoda grossa this crescent is often completely absent.

11mm female Noble False Widow Spider

9mm male Noble False Widow Spider 27th May 2017

12mm female Noble False Widow Spider 17th April 2018

Three combined images of a female Noble False Widow Spider photographed in its web by the front door of my home in SE London, 26th November 2020.

Here's an old friend that was always waiting to welcome us home every night. This female False Widow Spider (Steatoda nobilis) lived in a small hole on the white UPVC door frame of our front door for some time. We've had a False Widow Spider living there for several years now. Although False Widow Spiders have been recorded living for over five years it's possible that as soon as one specimen dies this idyllic spot is quickly reinhabited by a waiting suitor.

3mm sub-adult Steatoda nobilis found crawling on my chest in my SE London home. 23rd October 2021.

On 23rd November 2021 I searched a residential garden in North Kent at night in the hope of finding Steatoda bipunctata. This is the only address where I had previously found Steatoda bipunctata. Unfortunately I was unable to find a single specimen of S. bipunctata but I did find 36 Steatoda nobilis specimens in that garden. This further supports my belief that Steatoda nobilis is displacing native species of spider.

Female Noble False Widow Spider photographed in its web by the front door of my home in SE London, 26th November 2020.

Female Noble False Widow Spider

False widow webs are a messy tangled scaffold of silky threads. The Noble False Widow Spider is primarily a nocturnal species and at night can often be spotted hanging upside down in its messy hammock style web. During the day the spider usually hides away in a crack or crevice in the adjoining wall or fence, or under leaves of vegetation. 

Female Noble False Widow Spider

The much maligned Noble False Widow Spider (Steatoda nobilis) hanging in its web in my SE London garden 4th July 2021. I must admit that this one does look mean it the photo and the reflections of my flash on its fang casings give the impression of a sinister expression. The reality is these are a docile and slow moving species out of their web and are reluctant to bite.

Female Noble False Widow Spider, photographed in my SE London garden, 8th August 2021

Female Noble False Widow Spider, photographed in my SE London garden, 8th August 2021

Sub-adult male Noble False Widow Spider, Steatoda nobilis. One of over 50 specimens in my SE London garden 14th May 2022.

Sub-adult male Noble False Widow Spider, Steatoda nobilis. One of over 50 specimens in my SE London garden 14th May 2022.

This sub-adult male specimen was almost adult size. When viewed from above it looked very much like an female specimen. However the large rotund abdomen of the female is also often seen on juvenile and sub-adult male specimens too. When viewed from underneath the slightly bulbous tips of the male Steatoda nobilis are clearly visible. This is why it's important to see the tips of the pedipalps to correctly sex a sub-adult specimen. However, once the legs become uniform in colour, and carapace turns very dark black, the shape of the male abdomen is usually less "globular" and is often a good indicator of the sex, if you can't see the pedipalps. The wider carapace is also another indicator of a male specimen. 

Noble False Widow Spider, Steatoda nobilis. One of over 50 specimens in my SE London garden 14th May 2022.

Noble False Widow Spider, Steatoda nobilis. One of over 50 specimens in my SE London garden 14th May 2022.

Male Noble False Widow Spider, Steatoda nobilis. One of over 50 specimens in my SE London garden 14th May 2022.

Male Noble False Widow Spider, Steatoda nobilis. One of over 50 specimens in my SE London garden 14th May 2022.

Male & sub-adult female Noble False Widow Spiders, Steatoda nobilis. One of over 50 specimens in my SE London garden 14th May 2022.

This photo shows a male and a sub-adult female Steatoda nobilis sharing the same web. They were seen in the web together every night of the week before this image was taken. Whilst these two could just be tolerating each other it's highly likely that the male is safeguarding the sub-adult female from rival males, until she reaches maturity and is able to copulate. 

How can we tell this is a male and sub-adult female? The swollen tips of the pedipalps can clearly be seen on the first spider, and are completely lacking on the second, so the sex of both specimens is clear. The female was half the size of an adult specimen. The size, shape, colouration and abdominal pattern of the female's abdomen are also indicative of a sub-adult specimen. The female is still showing the slightly annulated legs of a sub-adult as well.

Female Noble False Widow Spider, photographed in my SE London garden, 21st March 2022

This large adult female Steatoda nobilis was so heavily gravid that she could hardly walk. At this vulnerable stage she's easy prey for the Giant House Spiders, Stone Spiders and Cellar Spiders that she shares my garden shed with.

Female Noble False Widow Spider, photographed in my SE London garden, 21st March 2022

This image clearly shows the arrangement of the 8 eyes of Steatoda species.

8mm female Cupboard Spider / False Widow Spider (Steatoda grossa)

False Widow Spider  /  Cupboard Spider  (Steatoda grossa)

Steatoda grossa is another of the UK's False Widow Spiders. A fairly common species which usually prefers a slightly different habitat to the Noble False Widow Spider. Although both species are generally synanthropic, being found around homes and buildings, Steatoda grossa prefer to reside in dark places such as sheds and outhouses, as well as the common name suggests, in cupboards in houses. Steatoda grossa have adapted well to the dry conditions of our homes and can last for months without food or water if necessary. The specimen above was found under a manhole cover above a sewage outlet in my garden in SE London / North Kent. Whilst the conditions within the cupboards and sheds, where Steatoda grossa are frequently found, are usually very dry habitats the Steatoda grossa that live under the manhole cover in my garden show this species can also thrive in this very damp environment too. Because of the dark habitats that Steatoda grossa favour their main food source is often woodlice, that share these habitats.

Female Steatoda grossa have a maximum body-length of around 6.5 - 10mm but the males tend to be slightly smaller and slimmer at around 4 - 7mm. Females can live for around six years in captivity but often only live to around 18 months in the wild. Males usually die after mating. The most distinguishing feature of Steatoda grossa are the two or three triangular or chevron markings on the top of the abdomen, which are not always present on larger female specimens. The foremost light chevron marking rarely touches the light abdominal band at the front of the abdomen. 

Although widely established across England and Wales, with a scattered distribution in the north of the UK, Steatoda grossa was only first recorded here in the UK at several sites in the south of England, around the year 1900. Although its history before this date is unclear it is likely that Steatoda grossa  is not originally native, and like Steatoda nobilis, has been accidentally introduced to the UK. It is widely regarded that for a species to be considered as native it generally has to have been here since the last ice-age, or it has to have become established and naturalised here without deliberate or accidental assistance from humans. It's likely that Steatoda grossa does not fit into either definition and therefore could not be regarded as native to the UK. It would be interesting to see how common and widespread Steatoda grossa was in the UK 75 years ago. It's distribution, like Steatoda nobilis, was probably very patchy and localised, pointing to the likelihood of multiple accidental introductions over the years.

Steatoda grossa was not originally assigned to the Steatoda genus at all. Even literature from the 1970's refers to this species as the large Theridion spider, Teutana grossa. Until Steatoda nobilis was excepted as established in the UK Steatoda genus was regarded as the largest Theridon species found here.

8mm female Cupboard Spider / False Widow Spider (Steatoda grossa)

Although not dangerous, the bite of the Cupboard Spider is known on occasion to be moderately painful to humans, but does not cause long term issues. On very rare occasions a bite can cause steatodism, which symptoms can include the site of the bite to blister and the victim could suffer muscle spasms, pain, fever and sweating. The antivenin for Latrodectus sp. (Black Widow Spider) is known to be effective in treating serious bites from Steatoda grossa.

LINK 1    LINK 2    LINK 3

2mm Cupboard Spiderling / False Widow Spiderling (Steatoda grossa), found in my understairs cupboard, 19th June 2019. 

3mm Cupboard Spiderling / False Widow Spiderling (Steatoda grossa), found wandering on my bed, 11th June 2020. 

10mm female Cupboard Spider / False Widow Spider (Steatoda grossa), found under a manhole cover in my garden in SE London, 3rd May 2020.

The markings on the abdomen of Steatoda grossa fade with age and larger female specimens, particularly gravid specimens, can sometimes show no markings at all, such as the specimen pictured above and below. Usually when the abdomen is uniform in colour it is a dark plum or reddish brown colour. Very occasionally though specimens with a bright red abdomen have been observed, as with this specimen here in Crantock, near Newquay, in Cornwall:  LINK 

10mm female Cupboard Spider / False Widow Spider (Steatoda grossa), found under a manhole cover in my garden in SE London, 3rd May 2020.

7mm male Cupboard Spider / False Widow Spider (Steatoda grossa), found under a manhole cover in my garden in SE London, 3rd May 2020.

7mm male Cupboard Spider / False Widow Spider (Steatoda grossa), found under a manhole cover in my garden in SE London, 3rd May 2020.

10mm female Cupboard Spider / False Widow Spider (Steatoda grossa), found under a manhole cover in my garden in SE London, 18th October 2020.

In addition to this adult female False Widow Spider (Steatoda grossa) there were also several tiny 1-2mm spiderlings on the underside of the manhole cover in my garden.

4mm sub-adult male Steatoda bipunctata, found on a garden shed in Gravesend, Kent, 27th June 2021.

Rabbit Hutch Spider / Common False Widow  -  (Steatoda bipunctata)
The Rabbit Hutch Spider is often associated with outbuildings, sheds, garages, rabbit hutches and chicken coops. It is believed they are likely to be a native species to the British Iles and are common and widespread across the UK. It is likely that Steatoda bipunctata may have been displaced in some areas that now have a large presence of Steatoda grossa and Steatoda nobilis. Steatoda bipunctata are still far more common than either S.nobilis or S.grossa in the northern half of the UK. Steatoda bipunctata are smaller than either Steatoda nobilis or Steatoda grossa and have a body-length of around 4-7mm for females and 4-5mm for males. This False Widow is usually characterised by the central stripe that runs down the middle of their abdomen. This stripe is regularly broken or in some cases just a series of dots. The line that runs around the base of the abdomen is also usually broken or dotted. The Rabbit-Hutch Spider also often has four dots on its abdomen.

Mature males are easy to distinguish from other species of the Steatoda genre by their large and easily recognisable pedipalps. The underside of the Rabbit Hutch Spider makes identifying this species easier as they often display a distinctive dark marking that resembles the "Alpha" symbol of the Greek alphabet. This is obviously easier to see on lighter specimens. Although considered common and widespread this species has taken me ten years to find in the SE of England. It is possible that Steatoda bipunctata is being displaced by the larger non-native Steatoda nobilis in some cross-over habitats the species share. The sub-adult male Steatoda bipunctata pictured above was a single specimen, found at night, on a garden shed surrounded by 13 Steatoda nobilis. The smooth unstructured pedipalps indicate this is not a mature specimen.

LINK 1    LINK 2    LINK 3

4mm sub-adult male Steatoda bipunctata, found on a garden shed in Gravesend, Kent, 27th June 2021.

13mm adult female Steatoda paykulliana

Mediterranean False Widow Spider  /  Eastern  False Widow  (Steatoda paykulliana)

Another of the False Widow species sometimes found in the UK, with a body-length of around 8-13mm for females and a leg-span of up to 35mm. Males are smaller at 4.5 - 7mm in body-length.

Steatoda paykulliana is a species from the Mediterranean that regularly find its way to the UK amidst imported grapes and other fruit. At the moment this species has only been found on very isolated occasions living wild in certain areas in England. These isolated cases are probably due to Steatoda paykulliana specimens arriving here as an accidental stowaway amidst imported fruit and then being released into the wild by the finder. However there is no evidence available to substantiated any claimed reports of Steatoda Paykulliana being found wild and established anywhere in the UK. 

With its dark black body, and often red markings, this is the species most likely to be mistaken for the far more venomous Black Widow Spiders of the Latrodectus genus, which are not present in the UK but do very occasionally turn up amidst imported fruit. The red markings on the Mediterranean False Widow can also be yellow, orange or white instead of red. However Steatoda paykulliana do not possess the red hour-glass marking usually present on the underside of Black Widow Spiders.

The bite of Steatoda paykulliana can be quite painful, but it is generally regarded to be of little or no medical significance to humans. Steatoda paykulliana, like other False Widows in the Steatoda genus, are not aggressive and bites to humans are rare in the Mediterranean countries where Steatoda paykulliana are native. In laboratory conditions, during the 1960's & 70's when such tests were more acceptable, Steatoda Paykulliana has been proven to have a venomous bite powerful enough to kill small mammals though, including mice and even large guinea pigs!  (see page 26) LINK. The French INPN (The National Inventory of Natural Heritage) reports that in laboratory conditions Steatoda Paykulliana has been proven to kill adult rats and cause temporary paralysis in rabbits. LINK

Nearly all Steatoda paykulliana specimens that arrive in the UK amidst imported fruit are juveniles. Due to their size it would be much harder for adult specimens to hide undetected. As juveniles the female specimens that arrive in the UK have no chance of turning up in a gravid state, and therefore cannot reproduce and spread, unless by chance there happened to be juveniles of both sexes accidentally brought into the UK in the same shipment. Juvenile and sub-adult Steatoda paykulliana look quite different to the adult females and have annulated legs, tend to be brown in colour and often have cream coloured markings, making them easier to mistake for other Steatoda species. The abdominal markings are often referred to as resembling fish bones. As the female spider matures the abdominal markings change and take on the brighter red, yellow, orange or white appearance as the rest of the spider turns to a very dark black colour. Often pictures of Steatoda paykulliana found in books only show the spider as a fully developed adult, which obviously looks quite different from the sub-adult specimens that turn up as accidental stowaways amidst imported fruit. Adult male Steatoda paykulliana tend to look quite similar to sub-adult specimens. Adult males usually have orangey-brown legs, which are notably darkened at the joints, and a dark brown abdomen, which usually still displays the white / cream coloured fishbone markings. The tips of the male's pedipalps are slightly swollen and pointed in shape.

It's often reported that any accidentally introduced colonies of Steatoda Paykulliana would be able to survive our winters in most parts of the UK, and that this would only change if our winters were to become milder in the future. However Steatoda Paykulliana is winter-resistant and has been found at altitudes of 700m in West Bulgaria, where the winters are quite severe and the snow stays on the ground for some time due to the adjacent low mountains. It seems Steatoda Paykulliana is probably not as adaptable to new and varying habitats though as Steatoda nobilis, which has thrived since being introduced to the UK, and requires more specific conditions to successfully breed. Where I have found Steatoda Paykulliana in Cyprus and southern Spain the conditions were very hot and very dry and the spiders were found hidden away in darkness beneath rocks on sandy soil at coastal sites. This xerophilic species seems to require hot, dry conditions with low humidity, where it can build its webs low to the ground. The most obvious places that would appear to meet its needs would be within human habitations, and yet within its natural range Steatoda Paykulliana is usually found outside of homes. 

Could Steatoda paykulliana be established anywhere in the UK?

I believe it's likely that at some point in the future Steatoda Paykulliana will adapt and will probably find parts of the UK that are suitable to its requirements and that will allow it to become established here. There have been isolated specimens of Steatoda Paykulliana being found living in the wild in the UK in the past. In 2008 the BBC featured an article about exotic spiders in the UK, and when discussing Steatoda paykulliana they had a quote from Stuart Hine, who ran the Insect Identification Service at the Natural History Museum, and according to the article Stuart claimed Steatoda paykulliana were already established in the UK back in 2008. He went on to say: "Now we have found it in Plymouth. And it looks as if it is here to stay".  LINK   Stuart Hine has since been in touch with me (October 7th 2021) to clarify this situation, and it seems the press misquoted him and got their facts wrong. So although the occasional specimens have been found in the wild here in the UK there is no proof Steatoda Paykulliana have ever become established anywhere in this country.

There were also some speculative records from Kent, near a fruit import warehouse in 2008. Other sources claim sightings from Dorset, Milton Keynes, Plymouth and Tilbury Docks in Essex. The Plymouth sightings have already been ruled out as a mistaken identification of Steatoda nobilis. The claimed colony at Tilbury Docks was reported to be around the site of a major fruit importer so this is definitely feasible and may the Steatoda paykulliana colony have existed there at some point in the past. However any possible colonies that may have once become established in the UK for a short while died off quite quickly. There was a claim of Steatoda Paykulliana having previously become established in a conservatory and outbuildings in Dorset back in 2017. Unfortunately with no photographic evidence to substantiate this report it cannot be confirmed.   LINK

As far as experts are aware this species is not currently established anywhere in the UK and has not been proven to successfully breed here either. To the best of my knowledge there is no real reason why this species couldn't become established at suitable sites in the UK at some point in the future though.

I'd love to hear from anyone that has recent photos of these spiders seen at a site in the UK. Please get in touch with a photo.  email

11mm adult female Mediterranean False Widow Spider   (Steatoda paykulliana)

This female specimen has an unusually shrivelled abdomen due to having just produced and egg-sac, which it was guarding when I found it under a large rock in Paphos, Cyprus. These spiders can have a red, yellow or white band around the abdomen. Sometimes they display a midline pattern on their abdomen which can consist of a stripe or a series of triangles or chevrons. In their native countries the Mediterranean False Widow Spider is usually found low to the ground in dry and semi-dry environments with sparse vegetation. Ideal sites include dunes, moors and heathlands, where they are usually found in cracks in walls or under rocks. Other places where Steatoda paykulliana are frequently found include log piles and disused mammal burrows. Mature females usually produce several large, white, fluffy egg-sacs that are as large as the female herself.

LINK 1    LINK 2    LINK 3    LINK 4    LINK 5    LINK 6

5mm juvenile Mediterranean False Widow Spider (Steatoda paykulliana) found amidst imported Spanish grapes. 6th October 2021.

This Mediterranean False Widow Spider (Steatoda paykulliana) found its way into the UK, as many of this species do, amidst imported white grapes from Spain in October 2021. The grapes were bought in Cornwall by Anne-Marie Young, who very kindly sent the spider to me to photograph and raise. Due to being a non-native species this spider cannot be released into the wild so will now be raised by myself in captivity.    LINK    This juvenile Steatoda paykulliana specimen is typical in its appearance of others of this species that arrive in the UK amidst imported fruit. Nearly all Steatoda paykulliana specimens that arrive in the UK amidst imported fruit are juveniles and exhibit this dehydrated and underfed shrivelled abdomen.

These photos of this Steatoda paykulliana were posted on Facebook and proved to be one of the most popular posts I have ever shared, with over 500 likes.  LINK

Steatoda Paykulliana found in the UK as accidental stowaways.

My research into Steatoda Paykulliana has now found 26 confirmed records of this species arriving in the UK amidst imported fruit & veg, from 2014 - 2021. Eighteen of these records have come from 2020 and 2021, suggesting that this species is probably arriving in the UK more often now than in previous years. The COVID 19 lockdowns of 2020 and 2021 may also have had an effect on the number of sightings being photographed and reported as many people found themselves with more time on their hands during this period. It'll be interesting to see if this current trend continues as society returns to normality, and I'll be keeping a close eye out for new records of paykulliana in the UK over the next couple of years. The most common method of travel appears to be hidden amidst imported grapes, especially those from Spain. One record came from raspberries imported from South Africa, one record came from grapes imported from Greece and one came from Broccoli imported from Spain.  LINK

If the number of non-native Steatoda and Latrodectus species being found in the UK amidst imported fruit are on the increase, what are the reasons behind it? One theory, based on a claim by the Daily Mail in a story they ran on 26th November 2002, suggests that these spiders are being deliberately introduced into vineyards as a form of biological pest control to protect the grapes from other insects. LINK. The BBC ran the story the following day claiming that Tesco had strongly denied any deliberate use of Latrodectus species in their vineyards, but admitted that their policy to try and use less pesticides on their fresh produce could result in more spiders finding their way into imports of fruit and vegetables. LINK

5mm juvenile Mediterranean False Widow Spider (Steatoda paykulliana) found amidst imported Spanish grapes. 6th October 2021.

At 5mm in length this Steatoda paykulliana is quite difficult to identify the sex with 100% accuracy. At this stage both male and female specimens look extremely similar. Females will continue to grow in size and will become very dark black. Females will also lose the annulations on their legs and the abdominal markings will become bright white, red, orange or yellow. Males however, will not usually grow much larger than this at 5mm. Males will usually not change much in appearance either, and will retain this colour, markings, and usually also the annulations on their legs too. The subtly swollen tips to the male's pedipalps will develop as it reaches maturity but are often easily missed when viewed from above.

*  I would like to give huge thanks to Anne-Marie Young for sending me this juvenile specimen to photograph, add to my website, and raise in captivity.  *

5mm juvenile Mediterranean False Widow Spider (Steatoda paykulliana) found amidst imported Spanish grapes, 6th October 2021.

Stuart Hine, who previously ran the Insect Identification Service at the Natural History Museum, made the following comments on my images of Steatoda paykulliana:
"The ones I have reared have all lost the fishbone pattern in the last molt, leaving just a silvery band on the anterior of the opisthosoma. As they age this gradually turns yellow to orange and finally red. I’ll be interested to see if you find the same."

9mm female Mediterranean False Widow Spider (Steatoda paykulliana) 26th December 2021.

Photographed nearly 12 weeks after being taken into captivity it is now far easier to determine the sex of this Mediterranean False Widow, Steatoda paykulliana, as a female specimen, with no visible development of palpal bulbs and a large rotund abdomen. During the 12 weeks in captivity this spider has fed well on a once a week supply of flies and mealworms. The body-length has grown from 5mm to 9mm. The previously shrivelled and dehydrated abdomen is now very plump, with a healthy glossy sheen. The abdominal markings have faded from a creamy white colour to a light brown colour. The annulations on the legs are now only just visible.
The spider could reach a final body-length of around 11-13mm. As Steatoda paykulliana mature the abdominal markings typically continue to fade before turning yellow, then orange and finally red. The abdomen and legs will continue to darken and will eventually be completely black. This species does sometimes vary in appearance with its abdominal markings as it matures. Some adult specimens completely lose their abdominal markings when viewed from above and just retain the pale, or coloured band at the front of the abdomen. Other specimens retain some or all of their upper markings as the spider matures and these marking just change colour. The abdominal markings of most female specimens will change from cream / white to yellow, then orange, and finally red, but the markings of some specimens may remain in either white, yellow or orange even once the spider reaches maturity. Some specimens lose all markings entirely and the spider matures to be completely black.

11mm female Mediterranean False Widow Spider (Steatoda paykulliana) 9th February 2022

Photographed 4 months after being taken into captivity as a juvenile, this mature female Steatoda paykulliana has reached a body-length of 11mm and has completely lost all abdominal markings. The only hint of colour remaining at this stage are the slightly reddish-brown tips of the legs, which also turned completely black within a few weeks of these photos being taken.

11mm female Mediterranean False Widow Spider (Steatoda paykulliana) photographed in captivity, 1st May 2022

11mm female Mediterranean False Widow Spider (Steatoda paykulliana) photographed in captivity, 1st May 2022

11mm female Mediterranean False Widow Spider (Steatoda paykulliana) photographed in captivity, 1st May 2022

11mm female Mediterranean False Widow Spider (Steatoda paykulliana) photographed in captivity, 1st May 2022

11mm female Mediterranean False Widow Spider (Steatoda paykulliana) photographed in captivity, 1st May 2022

4.5mm adult female Triangulate Cobweb Spider (Steatoda triangulosa)

Triangulate Cobweb Spider / Triangulate Combfoot Spider  - (Steatoda triangulosa)
The Triangulate Cobweb Spider is a small and rare species of False Widow Spider, found occasionally in England. Most records are from specimens found around houses and its webs are usually made low to the dirt to catch crawling insects, particularly ants, woodlice and ticks. It's also not uncommon for these spiders to make their webs around window frames of human habitations, to catch flying insects. Females grow to a body-length of around 4-5mm and the slightly smaller males 3.5-4mm. It is not clear whether Steatoda triangulosa is a fully native species to the UK, an established non-native or an accidental and occasional import, although the latter is most likely. The Triangulate Cobweb Spider has very distinct zig-zag markings on its abdomen which make it easy to identify. In western Europe and North America, where this species is common, it is known to prey on small spiders considered dangerous to man, including the Recluse Spider. There are no records of the Triangulate Cobweb Spider ever biting humans though, and the venom of this spider is not significant to humans either.

*  I would like to give huge thanks to Gen Popovici for sending me this specimen to photograph and add to my website.  *

4.5mm adult female Triangulate Cobweb Spider (Steatoda triangulosa)

4.5mm adult female Triangulate Cobweb Spider (Steatoda triangulosa)

Both of the non-native False-Widow spiders, Steatoda paykulliana and Steatoda triangulosa are found occasionally in the UK. Steatoda paykulliana usually turn up amidst imported fruit, whilst the much smaller Steatoda triangulosa seem to turn up amidst imported plants.
Some specimens of Steatoda paykulliana, particularly sub-adults and males, can exhibit abdominal markings slightly similar to those found on Steatoda triangulosa. Using photos of both species I have created this image showing the difference in typical abdominal markings between the two species. Both species can have brown annulated legs as a sub-adult. As they mature the differences are very obvious and Steatoda paykulliana take on a much darker, usually very dark black appearance. The abdominal markings on Steatoda paykulliana fade as the spider ages but those markings that are retained can vary in colour from white, orange, yellow or red. Steatoda triangulosa always retain their brown and cream colours and their triangulate abdominal markings as an adult. Only a minority of older female Steatoda paykulliana retain their upper abdominal markings and the majority of specimens lose most markings apart from the red band at the front edge of their abdomen.

White-Spotted False Widow Spider - (Steatoda albomaculata)
A rare and locally distributed small species of False Widow Spider found in the south and south-east of England on dry sandy heathland, shingle or under stones. The White-Spotted False Widow spins its web in low vegetation, often between large stones. This species is often found in areas with large numbers of ants upon which it readily preys. Females grow to around 3-6mm and males 4-5mm.

Tangle Web Spider - (Steatoda / Asagena phalerata)
Since being reclassified from the Steatoda genus to the Asagena genus there could be some debate as to whether the Tangle Web Spider should still be regarded as a False Widow Spider or not. This uncommon species is small with a maximum body-length of less than 6mm. It is usually found at ground level ,in dry sunny places, with little vegetation and sand dunes. It is common found in the vicinity of ants, which form most of its diet. The Tangle Web Spider rarely uses any silk to catch and subdue its typical ant-prey, suggesting that its venom is highly effective and fast acting on ants. It can often be found hunting around ants nests.

LINK 1    LINK 2    LINK 3

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Black WidowsLatrodectus species.

There are no spiders more infamous than the highly venomous Black Widow Spiders. The Latrodectus genus of Widow Spiders currently contains 34 different species, that can be found in warmer countries across the world. This includes the two recently described species (Latrodectus garbae and Latrodectus hurtadoi) from Colombia. (See full list here).

But are the Black Widows really as deadly as their reputation suggests? Although Latrodectus species do have a medically significant bite there are very few human fatalities as a result. Not all Latrodectus species are equally dangerous though. Latrodectus mactans, which is commonly referred to as the Southern Black Widow, is a common species found in the southern states of the USA. Although bites from this species are both painful and extremely unpleasant, no one has actually died as a result of a bite from a Southern Black Widow. YouTuber "Jack's World of Wildlife" filmed himself taking a severe envenomation from this species which can be watched here: LINK. Although the Black Widow has a reputation of being deadly to humans there have been no confirmed deaths recorded as a result of bites from any of the 5 species of Latrodectus spider found in the USA for many years. From the year 2000 until the year 2008 there were 23,409 records of bites to humans from Latrodectus spiders in the USA, and none of these bites resulted in fatalities. LINK

It's important to remember that no species of Black Widow, or other Latrodectus species, are established anywhere in the UK. 
The UK Government once debated the risk of the Black Widow Spider becoming established in the UK, as far back as 1927. These spiders were deemed at that time to be of no risk to the UK - LINK  Very occasionally though juvenile specimens or egg-sacs do turn up in the UK, usually amidst imported fruit. Adult specimens of Latrodectus species have also turned up on very rare occasions, as accidental imports hidden amidst other imported goods, particularly cars. Below are a few recent examples of such finds:

Recent records of Latrodectus species found in the UK

1)  On 12/01/2020 a Brown Widow, Latrodectus geometricus, with its egg-sac, was found in in Cwmbran, Wales, amidst imported black grapes bought from Asda, and originating from Brazil.    LINK    LINK 2    LINK 3

2) On 15/03/2016 three egg-sacs of the Brown Widow, Latrodectus geometricus, were found amidst imported red grapes in Wokingham, Berkshire.  LINK

3)  A Juvenile Mediterranean Black Widow, Latrodectus tredecimguttatus, was found amidst imported red grapes from Egypt, bought at Sainsburys, July 15th 2021   LINK

4)  On 20th November 2021 A pest controller was called to deal with 11 specimens of both male and female Western Black Widow Spiders, Latrodectus heperus, found amidst wooden pallets on a shipping container in Rochdale. The shipment had come from California, where they have both Southern and Western Black Widows. However the feint lighter banding on the legs of these spiders identified them as Western Black Widow Spiders, Latrodectus heperus rather than the Southern Black Widow Spiders, Latrodectus mactans.  LINK

5)  On 3/06/2015 an adult female Black Widow Spider and her spiderlings were found in a punnet of white grapes imported from Mexico, and bought from Asda in Leamington Spa, Warwickshire.  LINK

6)  In March 2022 an adult female Latrodectus sp. was found in a warehouse in Billericay, Essex, that imports cars from northern USA. Unfortunately the spider was destroyed before it could be accurately identified or rehomed.  LINK   In the USA, where it's believed this spider originated from, there are 5 species of Latrodectus spider that can be found in various different states. These include: 

Latrodectus Geometricus, the Brown Widow
Latrodectus heperus, the Western Black Widow
Latrodectus variolus, the Northern Black Widow
Latrodectus mactans, the Southern Black Widow
Latrodectus bishopi, the Red Widow

Only two of these Latrodectus species have the feint lighter banding on the legs, as seen on the specimen found at Billericay, so the spider's identity could be narrowed down to one of these two species. One is Latrodectus Geometricus, the Brown Widow, and the other is the Western Black Widow, Latrodectus heperus

7) On 20th March 2022 an adult female Brown Widow, Latrodectus geometricus, was found amidst red grapes, bought from Tesco in Bellshill, North Lanarkshire, in Scotland, and imported from South Africa. Unfortunately the spider was dead on arrival.  LINK

8) On 9th March 2022 an adult female Brown Widow, Latrodectus geometricus, was found amidst white grapes bought from Asda in Middleton, Greater Manchester, and imported from South America. Unfortunately the spider was accidentally killed on discovery. I'm very grateful that the dead specimen was sent to me to photograph and identify. See images below.  LINK   Once photos were taken the dead spider was then forwarded on to Dr John Dunbar, at Venom Systems & Proteomics Lab at The Ryan Institute Zoology, for DNA analysis. 

Deceased 9mm adult female Brown Widow, Latrodectus geometricus, found amidst white grapes imported from South America, 9th March 2022

Deceased 9mm adult female Brown Widow, Latrodectus geometricus, found amidst white grapes imported from South America, 9th March 2022

7mm spiky egg-sacs belonging to the Brown Widow Spider, Latrodectus geometricus, found amidst imported grapes from Brazil, 7th November 2021.

9)  On the 7th November 2021 Sarah Burgin, from Crewe, Cheshire, found four spiky egg-sacs hidden amidst her Brazilian black grapes, purchased locally. The spiky egg-sacs are distinctive and can only belong to the Brown Widow, Latrodectus geometricus, a species commonly found in Brazil, where the grapes originated from. Three species of spider from the Latrodectus genus are reported as occurring in Brazil: Latrodectus mactans, the Southern Black Widow, Latrodectus curacaviensis, the Brazilian Black Widow, and Latrodectus geometricus, the Brown Widow. However neither of the other two species create spiky egg-sacs.    LINK .  Fertile eggs of the Brown Widow usually take 14-21 days to hatch, but the spiderlings can remain hidden away within the egg-sac from just a few days to another month after hatching. When found it was uncertain whether these egg-sacs would prove to be fertile or not, and if fertile would they have survived the refrigerated transportation process used when exporting grapes? It's not uncommon for the Brown Widow to create several egg-sacs at a time, with as few as just one or more of those actually containing fertile spider eggs. 

7mm spiky egg-sacs belonging to the Brown Widow Spider, Latrodectus geometricus, found amidst imported grapes from Brazil, 7th November 2021.

Brown Widow egg-sacs, 1 - empty, 2 - undeveloped eggs, 3 - dead spiderlings.

Unfortunately the Brown Widow egg-sacs, found amidst imported grapes from Brazil, did not hatch. Eventually the decision was made to investigate why and the egg-sacs were cut open to see if they were fertile or not. Egg-sac 1 was empty and therefore infertile. Egg-sac 2 was full of undeveloped and unhatched eggs. Egg-sac 3 was full of tiny spiderlings that had died. It's clear that two of the egg-sacs would have produced Brown Widow spiders but unfortunately both the eggs and spiderlings had failed to survive, either because of the refrigerated transportation process used when the grapes were exported, or perhaps the grapes were treated with pesticides that had killed the developing spiderlings and eggs. 

Brown Widow / Brown Button Spider   (Latrodectus geometricus)
The Brown Widow is believed to have originated from South America, although its range now covers most pantropical and many subtropical areas around the world. Although this species does turn up in the UK occasionally, as an accidental stowaway amidst imported fruit and other goods, it is not established anywhere in the UK. The Brown Widow tends to be slightly smaller and usually far lighter in colour than other Black Widow species. Females grow to a body-length of around 7-10mm, whilst the far smaller males only reach 2-4mm. The appearance of the Brown Widow is highly variable but usually ranges from light grey to light brown in colour, with a black & white geometric pattern on the dorsal side of its abdomen, and annulated legs. Darker specimens do sometimes occur though and these can easily be mistaken for juvenile specimens of other Black Widow species, in countries where both species occur, such as the USA. The Brown Widow still possesses the trademark hourglass marking of Latrodectus species on its underside, but instead of it being bright red, as with most of its Black Widow cousins, its hourglass marking is orange, or occasionally yellow.

Bites from the Brown Widow are not usually as serious to humans as other Black Widow species. Although they still possess a potent neurotoxic venom, that effects nerve endings, the yield of that venom is believed to be far lower and the amount of venom injected during a bite is usually considerably less than other Latrodectus species. Most bites from a Brown Widow are not medically significant due to the low content of α-latrotoxin in their venom. The effects are usually confined to the bite area and in 2/3rds of cases result in localised pain, sometimes severe, for 1-2 days and minor swelling for 1-4 days. Sensitivity to venom varies from person to person though and occasionally some bite victims can experience the more severe reactions of Latrodectism usually associated with the more dangerous Black Widow species. One such case in the USA, back in 2008, resulted in a previously healthy, adult male victim needing hospitalisation, experiencing symptoms including severe pain, cramps, nausea & vomiting, and fasciculations in the pectoral and quadriceps muscles. LINK

The expanded distribution of the Brown Widow is, like Steatoda nobilis, believed to be a fairly recent adaptation of the species, and DNA testing of Brown Widow specimens from around the world shows very little variation. The Brown Widow is now classed as an invasive species in many areas and is believed to be responsible for displacing some other Black Widow species in their native countries. Latrodectus species tend to prefer dry habitats and in their native countries they're are often found around buildings. Where found away from human habitations their typical habitats can include wood stacks, rock piles, rodent burrows, and hollow tree stumps.

Like other Black Widow species the Brown Widow is not an aggressive spider and even when you invade its web its reaction is usually to either retreat to its place of hiding or drop to the ground and play dead. Bites to humans usually only occur as a result of the spider being accidentally trapped against human skin. Adult female specimens have also been known to defend their egg-sacs. The much smaller male of the Brown Widow Spider poses no risk to humans at all as its fangs are too small to penetrate human skin.

The Brown Widow produces a very distinctive spiky egg-sac. One egg-sac can contain as many as 120-150 eggs. Female Brown Widows produce an average of 23 egg-sacs during their lifetime. By comparison the egg-sacs of the Western Black Widow (Latrodectus hesperus) can contain around 300 eggs, but the female spider will only produce up to 10 egg-sacs in her lifetime. No other species of Black Widow produces the distinctive spiky egg-sacs produced by the Brown Widow and it is these unique egg-sacs that make this species easy to identify in the field. Fertile eggs of the Brown Widow usually take 14-21 days to hatch, but the spiderlings can remain hidden away within the egg-sac from just a few days to another month after hatching. It's not uncommon for the Brown Widow to create several egg-sacs at a time, with as few as just one or more of those actually containing fertile spider eggs. The newly hatched spiderlings are very pale with no visible patterning. They will moult before leaving the egg-sac. By their second moult the spiderlings start to display the typical hourglass marking on their underside. Initially this marking is white and can be quite difficult to see. After emerging from the egg-sac the spiderlings will stay close by in a group for some time, during which time cannibalism often occurs. They eventually disperse by ballooning in the wind on threads of silk.

The Widow spiders get their name from the behaviour sometimes associated with Black Widow Spiders, where the female spider may eat her male partner during, before or after copulation. This practice is common with the Brown Widow Spider. Where it was once thought that this was an aggressive act on the part of the female, studies of the Brown Widow now lead arachnologists to believe that this behaviour is similar to the matriphagy seen in other species of spider, but now on the part of the male, as he offers himself as a sacrifice to the female for the  growth and development of his offspring now inside the female. During copulation the male has frequently been observed to rotate himself 180 degrees and place his abdomen directly in front of the jaws of the female. This behaviour has also been recorded with the Australian Black Widow species, the Red Back Spider, Latrodectus hasselti.

LINK 1    LINK 2    LINK 3    LINK 4    LINK 5    BITE

Are Black Widows Venomous or Poisonous?
People are often very quick to respond to others when they ask if a spider is poisonous, by correcting them with the fact that spiders are actually venomous rather than poisonous. They point out that the term "poisonous" is reserved for things that are toxic when ingested, and the term for wildlife that injects its poison is "venomous".  So does this mean that spiders aren't poisonous, but they are venomous? No, not always. In fact recent studies have shown that adult Latrodectus species are not only venomous but they're also poisonous too when eaten by predators. Testing on mice, rats and rabbits has shown that body-parts, including the legs and abdomen, of Latrodectus species can be deadly when eaten. Tests on cockroach subjects confirmed that Latrodectus can also be deadly poisonous to insect predators too.

But the extent of their toxicity goes well beyond the adult spiders. Laboratory tests have shown that both juveniles and even the egg of Latrodectus tredecimguttatus also contain highly toxic proteins that can be deadly when eaten. It is highly likely that these levels of toxicity extend to the other Latrodectus species too. Interestingly, similar tests on other species of spider, including the highly venomous Recluse Spider, Loxosceles species, showed no toxicity at all when fed to mice.   LINK    LINK 2

Dangerous Wild Animal Species
In the UK there are only four genus of spider that fall under the Dangerous Wild Animals Act 1976. These include the Wandering Spiders (Phoneutria genus), the Sydney Funnel-web Spider (Atrax genus), the Recluse Spiders (Loxosceles genus) and the Widow Spiders (Latrodectus genus).

Black Widow further information:

Widow Spiders in the Americas  -  LINK  LINK 2

List of Latrodectus species  -  LINK    LINK 2