Black Widow Spider

12mm adult female Western Black Widow

There are no spiders more infamous than the highly venomous Black Widow Spiders. As of 2024 the Latrodectus genus of True Widow Spiders currently contains around 35 different species, that can be found in warmer countries across the world. This includes the two recently described species from 2021, Latrodectus garbae and Latrodectus hurtadoi, from Colombia, and the 2019 discovery, Latrodectus umbukwane, from South Africa. See the full list of Latrodectus species at the bottom of this page, or on the World Spider Catalogue. None of the Black Widow spiders are established anywhere in the UK though.

Black Widow Spiders, like their cousins the False Widow Spiders, are from the family Theridiidae, known as the Comb-footed Spiders, or Tangle-web Spiders. As with other members of the family Theridiidae the Black Widow Spiders build strong, but messy tangle-webs. At night they can be observed hanging upside down in the middle of their webs.

Black Widows have quite a reputation for being highly venomous, and even deadly on occasion. 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 deliberately 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 up until the year 2008 there were an incredible 23,409 records of bites to humans from Latrodectus spiders in the USA, and yet not a single one of these bites resulted in a human fatality - LINK. In Australia, where they have the Red-back Spider, the most venomous of the Black Widow species, there hasn’t been a single death attributed to bites from that spider in over 70 years. Yet in complete contrast, in the UK alone there are an average of at least 3 people killed every year by pet dogs. Despite these figures all Latrodectus species cannot be kept in captivity in the UK without a Dangerous Wild Animal Licence. And yet UK Law allows any of us to fill our homes with Staffordshire Bull Terriers, or Rottweilers, without any restrictions.

12mm adult female Western Black Widow

Western Black Widow - (Latrodectus hesperus)

The Western Black Widow, as it's name suggests, is found mainly on the western half of the USA, and is most common in the southwest states. Outside of the USA the Western Black Widow is also found in SW Canada and in Mexico. As with other Black Widow spiders the Western Black Widow has a very painful and medically significant bite, but fatalities to humans are extremely rare. Adult females typically reach a body-length of around 14-15mm. The males are considerably smaller, reaching a body-length of 3-6mm, and are not usually considered to be dangerous to humans.

The adult female is usually an entirely glossy black colour, with a red hourglass marking on the underside of the abdomen. The hourglass is usually unbroken, but can often display a black spot, or two, in the centre of the hourglass. The hourglass is fairly symmetrical, with the bottom half being slightly larger than the top half.

Juveniles and sub-adults are brown in colour, with light and dark brown annulated legs, and are sometimes confused with the Brown Widow, Latrodectus geometricus. The abdomen of immature specimens typically exhibits a wide longitudinal line that runs the length of the abdomen. This line can be red or white, and is often broken or in the form of several dots. This line is often retained to some degree through to maturity, but is rarely seen on aged specimens. The Redback Spider, Latrodectus hasselti, also has a similar red longitudinal line on its abdomen. However, the abdominal line on Latrodectus hasselti only usually runs from the rear of the abdomen to just over half way towards the front of the abdomen.

Distinguishing between Latrodectus geometricus and juvenile Latrodectus hesperus

12mm adult female Western Black Widow

Latrodectus hesperus found in Hertfordshire, October 2024

Whilst there are no Latrodectus species established anywhere in the UK we do get a few turn up here every year as accidental stowaways, usually imported from the USA, especially California, hidden on imported cars or amongst machinery. Black Widow Spiders have long been at the top of my wish-list for species to photograph. In November of 2024 I finally got an opportunity to photograph my first Black Widow spider. In this case it was an adult female Western Black Widow, Latrodectus hesperus, from Western USA.

On 28th October 2024 I was tagged in a Facebook post by Alice Bennett-West, one of the admin for the UK Spiders Group. Gareth Edwards had shared a photo on Facebook of a spider he believed to be a Northern Black Widow. The spider had been discovered in a large plastic storage trunk, in Gareth's residential garden, in north Hertfordshire. Gareth had recently received a shipment of animatronics equipment from Nevada, USA, and the spider must have hitched a ride to the UK. Once alerted to the Facebook post I immediately made contact with Gareth, who was happy for me to drive up to his house and capture the spider. I arrived there a couple of days later and Gareth immediately showed me to the storage trunk in his garden. Upon my arrival it was already dark and I was already equipped with a head-torch to help find the spider. Gareth opened the trunk and pulled back some of the items being stored there, and the spider could be seen sitting in the middle of a large scaffold-type web, typical of a Theridiidae spider. The large black spider was hanging upside down in its web with its bright red aposematic hourglass marking clearly visible. This marking serves as a warning to would be predators that this is a spider not to be messed with. The hourglass marking was complete, with the bottom half just slightly larger than the top half. Close inspection revealed that the hourglass also contained a couple of dark spots, typical of the Western Black Widow, Latrodectus hesperus. The origins of the spider also helped considerably with the identification. Northern USA has 5 Latrodectus species, but only the Brown Widow, Latrodectus geometricus, and the Western Black Widow, Latrodectus hesperus, are found in Nevada, and on the West Coast of the USA.

The quiet residential housing estate, in Royston, Herefordshire, where the Western Black Widow was found.

The messy horizontal web itself was built in a corner of the trunk, about 30cm from the ground. The web was about 25cm by 15cm in size. This dark, undisturbed spot is exactly the kind of location where I would expect to find the web of Steatoda grossa. When photographing or collecting Steatoda species in the wild it is also easy to find them hanging upside down in the middle of their web. However, when disturbed it is common for Steatoda species to flee from the web and disappear into their silken retreat, which is usually built at one corner of the web. This Western Black Widow had no obvious silken retreat. It was also far bolder than any Steatoda species that I have encountered. The Western Black Widow made no attempt to flee. Even though we were moving things out of the trunk, to allow better access to the spider, and my very bright head-torch was constantly shining on the spider, it did not move from the centre of its web. Because of the spider's reluctance to move from its web it's very easy to see how so many people are bitten by Latrodectus species in residential areas of the USA. It would be very easy for someone to accidentally place their hand on the spider without even seeing it. If the Black Widow isn't going to move out of the way then contact with humans is highly likely and it's usually only when people place their hands on these spiders that they become defensive and bites occur.

Because of where the spider's web was positioned I was unable to get a pot underneath the spider to catch it. I decided at this point that the safest way to catch the spider would be to use a net. As I placed my net through the web the spider finally made a move, and scurried to the edge of its web. I then rotated the net and slowly lifted the net upwards. As I did this the spider walked straight into the net. Once scooped out from the trunk the spider was quickly placed inside a secure container.

When first captured the shrivelled abdomen of this Western Black Widow shows the spider was dehydrated and malnourished.

Now that the spider had been caught it could be examined more closely. This was a mature and aged female specimen. It had just a fraction of its abdominal markings still visible at the front of its abdomen. The abdomen was small and shrivelled and the spider was clearly dehydrated and malnourished. Mature Latrodectus hesperus that arrive in the UK are nearly always gravid, and my attention now turned to searching for any signs of egg-sacs within the trunk. I was able to locate just one egg-sac that had been positioned at ground level, about 40-50cm from the rest of the web. This egg-sac appeared to contain no eggs though and was just a ball of silken thread. Due to the age of the spider it may have already used all the stored sperm to produce viable eggs in previous egg-sacs. There was also the possibility that further egg-sacs may have been produced elsewhere in the trunk, or even within Gareth's nearby garage. Gareth wasn't keen on me hunting through all his stuff to conduct a thorough search for egg-sacs, so we agreed that if he found any further Latrodectus spiders, or egg-sacs, then he would contact me again to arrange their removal. Latrodectus hesperus is a desert species, and prefers hot, dry conditions. It is unlikely that this species would be able to adapt to the damp climate of the United Kingdom and successfully become established in Britain. That doesn't mean that it couldn't survive here in heated buildings though, and close attention will need to be paid in case any egg-sacs or juvenile specimens turn up in Gareth's garage.

As with all Latrodectus species the Western Black Widow is listed as a DWAL species in the UK. This means that they can only be kept in captivity by licence-holders. The law does permit specimens to be held for up to 72 hours though by non licence-holders. This allows time for them to be captured and rehomed with a suitable keeper. Once home I contacted Chris Newman, of the National Centre for Reptile Welfare. Chris is the authority on non-native species in the UK and has been dealing with accidental imports of Latrodectus species since 1988. I agreed to deliver this Western Black Widow spider to Chris's Reptile Rescue Centre, in Tonbridge, Kent, at the weekend. In the meanwhile I now finally had the opportunity to photograph this Black Widow, a species I've been fascinated by ever since learning about them at school when I was just a young child.

12mm adult female Western Black Widow feeding on Banded Crickets.

Whilst in my care the Black Widow was kept in an enclosure that previously housed a Noble False Widow. The enclosure still contained the web of the Steatoda nobilis, which I use regularly as a prop to photograph other Steatoda spiders on. With the Black Widow also being a Theridiidae this spider builds a similar web to the Noble False Widow. This enabled me to photograph the Black Widow in the False Widow’s web.

Latrodectus species are not regarded as aggressive spiders and they usually only bite humans if they become trapped against our skin. I was surprised by the behaviour of this Western Black Widow during our first photo session though. When I photograph Steatoda species I generally use a very small artist’s paintbrush to gently tap the spiders to manoeuvre them into position, to obtain the best angles and to capture clean backgrounds in my shots. Now usually as soon as the paintbrush touches the spider they quickly shuffle forward an inch or two, but this Western Black Widow’s reaction was quite different. Every time I brought the paintbrush close to the spider instead of moving away it immediately turned its back and grabbed hold of the paintbrush with its rear legs, and started frantically trying to wrap the paintbrush in silk. It never actually tried to bite the brush but it certainly threw a lot of silken threads at it. This behaviour ceased as soon as the spider had been fed, confirming that rather than this being defensive behaviour it was clear that this was a natural feeding response from the Black Widow due the spider having not eaten for some time. My initial photos revealed just how shrivelled the spider’s abdomen was when it was found and I decided to try and feed it before taking any more shots.

I placed two small crickets into the spider’s web, but both crickets managed to immediately wriggle their way loose from the web and fell to the bottom of the enclosure. The Black Widow wasted no time in pursuing the first cricket and rapidly started throwing silk at it with its back legs. Once wrapped up the spider moved straight onto the second cricket and wrapped that one up too. Once both crickets were wrapped the spider then hoisted them both up into the top of the web and bound them both together. It was only at this stage that the spider inflicted bites on the crickets. It seemed strange to me that a spider with such a potent venom didn’t use its bite to subdue the crickets before wrapping them up. The spider fed on the crickets for several hours and once finished its abdomen soon looked full and healthy, and had now taken on the iconic globular shape associated with Widow spiders.

National Centre for Reptile Welfare, in Tonbridge, Kent. November 2024.

Come the weekend the Black Widow was then delivered to Chris Newman, at the National Centre for Reptile Welfare, in Tonbridge, Kent. Chris informed me that my adult female Latrodectus hesperus was actually on the smaller end of the size range that these spiders typically grow to as adult specimens. At 12mm my Black Widow already had a body-length comparable to that of an adult female Noble False Widow, Steatoda nobilis, but this Black Widow had a notably longer leg-span than any Steatoda nobilis. An adult female Latrodectus hesperus, with a 16mm body-length at the larger end of their scale, would certainly be an impressive spider to see. Chris also informed me that he usually deals with several accidental imports of Latrodectus species each year. My Western Black Widow was the fourth that he had encountered during 2024. The last specimen he dealt with was an adult female Red-back Spider, Latrodectus hasselti, which turned up at Dartford Crossing, following a delivery of equipment from Japan.

12mm adult female Western Black Widow

As a younger specimen this Western Black Widow would have had bright red abdominal markings, either in the form of a bold red longitudinal line, or a series of bold red dots. All that remains of these markings now on this aged female specimen are two very small red dots by the spinnerets.

12mm adult female Western Black Widow

12mm adult female Western Black Widow feeding on Banded Crickets.

12mm adult female Western Black Widow

12mm adult female Western Black Widow, Latrodectus hesperus.

The story of this Western Black Widow was shared in just one group on Facebook, the British Spider Identification Group. Incredibly the post quickly received over 1700 likes from other members, making it by far the most popular post I have ever posted on Facebook. It's great to see that so many people these days can appreciate the beauty of these elegant spiders. - LINK

In 2024 the American Red Cross were putting trainee staff through their Emergency Medical Response courses, to help them identify and treat spider bites in the USA. - LINK

It's interesting to see what's being taught on this course. Whilst these may be typical signs to look for, some victims may not experience all of these symptoms, but others may experience these and far more extreme symptoms. It's unusual to see any organisation recommending the bitten area be elevated though. The advice usually given to victims that have received a venomous bite is to keep the bitten area below heart level where possible, to reduce the venom spreading around the body.

Emergency Medical Response Officers are unlikely to witness most of the Recluse bite symptoms listed here either, as most of these symptoms occur long after the bite has taken place. Typically a red itchy rash is visible within 24-48 hours after the bite. In less than 10% of bites classic "bullseye" lesions can then start to occur at the site of the bite, becoming necrotic after 7-14 days and leaving a depressed ulcer.

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Are Male Black Widows Dangerous to Humans?

On most websites, especially those in the USA, you will find people claiming that only female Latrodectus species are dangerous to humans. Many websites claim that both males and juvenile females cannot pierce human skin, and therefore it's impossible for them to bite us. Some websites even claim that males do not have a venomous bite at all. I've been suspended from some Facebook groups for saying it but all of these points are incorrect.

The truth is male and juvenile Latrodectus species are not usually medically significant. The key word here though is "usually", as there are occasionally exceptions, and as such all Latrodectus species, regardless of sex or age, should be treated with respect. Yes, it is true that male specimens, and young female specimens, do have very small fangs, and it is often difficult for them to pierce human skin. However, if the male Latrodectus does find an area of thin skin then it can on occasion pierce the skin with its fangs, especially on young children, or the elderly, who have thinner skin.

It’s a complete myth that male spiders aren’t venomous. This common misconception is probably because with most arachnid species the males are often far smaller than the females, and with a smaller size comes a smaller venom yield, so bites are usually of no significance. With the exception of those species within the Uloboridae family all male spiders still use venom to subdue or kill their prey, just as their female counterparts do.

There has been extensive research in recent years on Steatoda nobilis, another species also from the sub-family Latrodectinae, by Dr JP Dunbar and his team. Their lengthy studies concluded that the sex of the spider played no part in determining the yield or potency of a venomous bite from Steatoda nobilis, or any of the other synanthropic arachnid species included in these studies. Males were shown to inject exactly the same venom during a bite as the females. The biggest contributing factor to the amount of venom injected was the size of the specimen, with the sex of the spider having no influence at all.

In fact with female Steatoda nobilis living a largely sedentary existence, and rarely leaving their webs, it is the mature males that typically enter homes during their search for mating partners. As a direct result, in the UK & Ireland, where Steatoda nobilis are extremely common, most human envenomations from Steatoda nobilis are defensive bites from male specimens, when they are accidentally laid or sat upon.

You can read one of JP Dunbar’s relevant papers here: High Venom Potency and Ability to Optimize Venom Usage Make the Globally Invasive Noble False Widow Spider Steatoda nobilis (Thorell, 1875) (Theridiidae) Highly Competitive against Native European Spiders Sharing the Same Habitats

With regards to male Latrodectus species, although the majority of bites could be dry bites, with little or no venom injected, the Australian Family Physician Vol. 33, made the following comments: “. . . it should be noted that a recent study reported the male redback spider occasionally may also cause latrodectism”

They refer to the following study: Isbister GK, Gray MR. A prospective study of 750 definite spider bites, with expert identifica- tion. Q J Med 2002;95:723–731.

Some years ago, on an exotic pet forum that no longer exists, I read two accounts from members warning other people to be careful when handling male Latrodectus species, as both members had received very unpleasant venomous bites from male Latrodectus specimens.

Mediterranean Black Widow Spider / European Black Widow (Latrodectus tredecimguttatus)

Most Black Widow Spiders can be easily separated from their False Widow cousins by the presence of the red "hourglass" marking on the underside of the abdomen. Adult females of the Mediterranean Black Widow are an exception though and do not typically posses the typical "hourglass" marking. It may however exhibit two small red dots or a red transverse line on the underside of its abdomen. Male specimens may exhibit the hourglass marking and it can be red or white where it does occur. - LINK LINK 2

The Mediterranean Black Widow is black in colour, like most others in the Lactrodectus genus. The Mediterranean Black Widow is distinguished by the thirteen spots on top its abdomen. These spots are white on juvenile specimens by change to red spots, which usually have a white border, as the spider develops. These markings often fade, or disappear completely, when the spider reaches maturity. Mediterranean Black Widows are regularly found on steppes (grassland plains without trees), other open grasslands and crop fields such as wheat. They are found in dry habitats such as sand dunes and sandy beaches with sparse vegetation. Although this species very rarely enters homes it has been recorded many times in green houses, where crops were being cultivated. Females grow to around 7-15mm, whilst the males are much smaller at 4-7mm.

As it's name suggests the Mediterranean Black Widow is found mainly within the Mediterranean region but has been recorded in the following countries: Albania, Armenia, Bosnia and Herzegovina, Bulgaria, China, Croatia, Cyprus, France, Georgia, Greece, Israel, Italy, Jordan, Kazakhstan, Kyrgyzstan, Lebanon, Macedonia, Portugal, Romania, Russia, Slovenia, Spain, Syria, Tajikistan, Turkey, Turkmenistan, Ukraine, Uzbekistan, Yugoslavia.

LINK 1 LINK 2 LINK 3 LINK 4 LINK 5 LINK 6 LINK 7

Despite visiting Cyprus on many occasions I have been unable to find a single Latrodectus tredecimguttatus specimen, despite extensive searches. The Mediterranean Black Widow has become quite rare on the island in recent years and this may well be partly due to the arrival of the non-native Brown Widow, Latrodectus geometricus, as it continues to expand its range. For more information visit this page of my website: Brown Widow in Europe.

Latrodectus tredecimguttatus was recorded in Cyprus May 19th 2018

"Many years back I was out with Snake George collecting Black Widows we found under stones in the Neo Chorio (Baths of Aphrodite) area." A record from Kazakhstan can also be viewed here: 15th May 1027

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Bites from Black Widow Spiders.

The venomous bite of the Black Widow contains neurotoxins and is considered to be both excruciatingly painful and "medically significant", and on rare occasion fatal to humans. Males, due to their considerably smaller size, are considered to be far less dangerous than females. Many online sources incorrectly claim that the males do not have a venomous bite. This is of course complete nonsense. It is true that the tiny male Black Widows have proportionally small fangs, that may struggle to pierce human skin. It is also true that the amount of venom such a small spider could deliver in a bite would be very small. However, if the spider did find a soft area of skin, and did manage to bite a human, then a person who was particularly sensitive to the venom could suffer exactly the same reaction to the bite that an average person would experience from the bite of a larger female specimen. There have been several records of this happening.

The initial bite is felt as a sharp "sting" followed shortly after by local pain, often accompanied by sweating, then regional pain, abdominal pain, painful lymph nodes, painful muscle cramps, nausea, hypertension, and malaise. The bite is often excruciatingly painful and completely debilitating, and can last from a couple of days to over a week. Emergency treatment should always be sought immediately after a Black Widow bite. Severe envenomations may require antivenin (IAuCSL05 Red-Backed Spider Antivenom produced by CSL Limited). Details can be found here: Red-Backed Spider Antivenom

Black Widow Bite Accounts.

1) Chris Newman, of the National Centre for Reptile Welfare, once recalled a bite he suffered from a Black Widow, and shared it on Facebook on 16th May 2020. Chris wrote: "I managed to be bitten by a very angry Latrodectus (black widow) whilst buggering about at an institution in London. The consequences of that bite were devastating, agonising beyond comprehension. At the time there was no antivenom in the UK for Latrodectus so treatment was simply to keep you breathing, the pain was intolerable and typical analgesics like morphine have no effect. Five days of excruciating pain can only be described as unpleasant in the extreme." - LINK

2) Allen Arellano, a resident in the Weld County, Colorado, USA, wrote the following account on Facebook after being bitten by a Black Widow: "Well this hitchhiker made my last 4 days a living hell....I was ambushed by this Black Widow last Sunday when I put my pants on ....She bit me in the back of my knee and started the most horrible muscle spasms and aches ive ever experienced in my life......I wouldn't wish that on my worst enemy,... I never imagined a spider could cause so much havoc on my body.........and 5 days later my head feels like its going to explode.......YIKES !!!" - LINK

3) In February 2024 Benata Smit, a researcher in South Africa, was bitten by a Black Button Spider (Latrodectus sp.), that was being held captivity. The sub-adult female specimen, believed to be Latrodectus indistinctus, was being studied in captivity and had not yet been formally identified as it hadn't reached maturity at this stage. Latrodectus species are usually shy and typically show no aggression when treated with respect. On this occasion the spider, that was originally captured from the wild in South Africa during October 2023, was already stressed after being transported from one location to another, to be studied in captivity. The spider was immediately defensive when taken out of its enclosure to be photographed, and it bit the researcher on her finger:

"I had the fortunate (for me) or unfortunate experience of having to endure, as the Africans would say, "big poison comes in small bottles". I was bitten by this beautiful black button spider (Latrodectus sp.). It’s important to note that the bite wasn’t caused by any harm imposed on the spider, as we generally assume that spiders have to be squashed / harmed before they bite. It was a humbling experience to say the the least.

It took a total of 25 minutes for me to experience the full brunt of the envenomation. She bit me on my left ring finger. In 5 min after she bit me my left elbow and shoulder started to pain. Another 5min and I started having trouble breathing. I was rushed to hospital and on arrival I couldn't use my legs. I had a typical case of Latrodectism where all my muscles started to contract; the pain was intense. It's a kind of pain you can't explain to anyone because it's so unique. When I arrived at the ER the doctor was very quick to react, even though it was their 1st black button spider bite case. They handled it very professional and knew exactly what to do to keep me calm and comfortable. Unfortunately there was no anti-venom at this specific hospital so they had to phone another hospital for anti-venom. The anti-venom arrived half an hour later. But in that half an hour it felt like I was dying. I was given a whole cocktail of pain and other meds to make sure I don't have any allergic reaction to the venom or anti-venom. I was administered the anti-venom immediately after it arrived. It took only 2 minutes for the anti-venom to take effect. I couldn't believe how quickly all the symptoms disappeared.

I was kept in High care for 24 hours, to be monitored and to make sure I don't have any allergic reaction to any of the meds I was given." - LINK

The toxicity of the venom of Latrodectus species varies from one species to the next, and even from one specimen to the next, depending on a variety of factors including geographic location.. These are the typical LD50 values for Latrodectus species found in Northern USA:

Brown Widow, Latrodectus geometricus = .43 mg/kg (in Florida) & .223 mg/kg (in Venezuela) LINK

Western Black Widow, Latrodectus hesperus = .84 mg/kg (IV) LINK / 0.64 mg/kg LINK

Southern Black Widow, Latrodectus mactans = 1.39 mg/kg (IV) & .90 mg/kg (SC) LINK / 0.26 mg/kg LINK

Red Widow, Latrodectus bishopi = 2.2 mg/kg (could be IP) LINK

Northern Black Widow, Latrodectus variolus = 1.8 mg/kg (IP) LINK / 1.20–2.70 mg/kg LINK

These can be compared with the Mediterranean Black Widow, Latrodectus tredecimguttatus = 0.59 mg/kg LINK

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Black Widows and Button Spiders in the UK - Latrodectus species

There are no species of Black Widow, Button Spider or other Latrodectus species, established anywhere in the UK. However, Latrodectus species have occasionally been known to arrive in the UK as accidental stowaways amidst imported goods. My research has lead me to find a number records of Latrodectus species arriving in the UK. Although the number of official records is very low I suspect the true number of Latrodectus species reaching the UK, hidden amidst imported goods, may be much higher. With the majority of such finds being made on commercial premises it is highly likely that most of these sightings are not recorded or reported. The Brown Widow, Latrodectus geometricus, arrives here on very rare occasions hidden in imported fruit. Brown Widows arriving in the UK usually do so hidden amidst imported grapes, and are nearly always dead on arrival though. It's unclear whether they succumb to the cold refrigerated temperatures during transportation or whether they die from the pesticides that are used to treat the fruit. Western Black Widows, Latrodectus hesperus, arrive here on very rare occasions, hidden in imported cars or machinery from the USA. And the Red-back Spider, Latrodectus hasselti, has occasionally been imported along with heavy machinery. In the UK no Latrodectus species have ever become fully established here in the wild though, largely due to our damp climate.

There are wild and unsubstantiated rumours and reports of previous introductions of Latrodectus species in the UK, whether intentionally or by accident. However, there is little or no evidence to support claims of most of these apparent introductions. Even if there was any truth to any of these rumoured introductions then the spiders certainly died out and failed to successfully establish viable, long-term breeding colonies in the UK, as there are currently no wild Latrodectus colonies in the UK today.

In August 2023 Chris Newman, the director of the National Centre for Reptile Welfare, informed me of two small, previous colonies of Latrodectus species in the UK, that he had personal dealings with. The first was the Western Black Widow, Latrodectus hesperus, which became established around a warehouse close to Heathrow Airport, that was the site of a large importer of fresh produce from California. The second site was at an undisclosed military base, where the Redback Spider, Latrodectus hasselti became established for a number of years. On both occasions these Latrodectus specimens were only established in synanthropic environments.

Chris Newman has been working with Latrodectus species in produce since 1988. During this time Chris worked for a number of importers / distributors, principally looking at Latrodectus hesperus. In Chris's opinion "Latrodectus hesperus is a species that could become established in the UK in localised areas, warehousing etc., but it is unlikely to become invasive as its intolerant of our damp winters." Chris went on to say "Latrodectus hasselti is another kettle of fish, so to speak. It has become established in Japan, in areas with winters not dissimilar to ours. This is a species that I personally think could become established in the UK, I’m not so sure about Latrodectus geometricus, I think it would be too temperature sensitive".

It's interesting that Chris believes Latrodectus hasselti should be regarded as the greatest Latrodectus threat to the UK though. Research that I read, published in October 2022, concluded the following though:

"Thus, despite the fact that human transport may regularly introduce L. hasselti spiders to new areas, our model suggests that the likelihood of establishment and spread will heavily depend on local humidity and temperature."

In Australia, where Latrodectus hasselti are native, it is believed they are being displaced in some coastal areas by Latrodectus geometricus. Observations there have shown that Latrodectus geometricus does have a preference for cooler areas when compared to Latrodectus hasselti though. Due to its sudden expansion in range in recent years many countries now consider Latrodectus geometricus to be highly invasive. As with Steatoda nobilis it's unclear why Latrodectus geometricus has suddenly expanded its range so dramatically in the last 10-20 years. - LINK

One source of unsubstantiated claims comes from the 2007 book "Venom", written by BBC presenter, Steve Backshall. On page 39 the book claims:

"There are definitely members of the Latrodectus genus doing very well in small pockets around Britain. The question is whether they are relict populations of an indigenous arachnid, or more recent imports. If the latter, have they arrived here under their own steam or by hitchhiking with humans? Certainly the proliferation of black widows around the caravan site of an arachnid breeder in Kent is due entirely to tiny spiderlings ballooning once they have left the egg-case. This is the process many spiderlings use to travel away from their siblings - they will climb up to a suitably high vantage point and eject a stream of silk, which then gets caught in the wind, carrying the enterprising Phileas Fogg-esque juvenile off into the air. Spiderlings can travel immense distances this way - potentially across the Atlantic, and certainly across the English Channel."

When I researched these claims this book was unfortunately discredited as inaccurate by expert arachnologist, Martin Bell, who makes specific reference to total inaccuracies on the book's information on Phoneutria venom. Although I'm a fan of Steve Backshall the book lists no references to substantiate its claims of Latrodectus colonies being found in the UK, and therefore cannot be regarded as reliable unfortunately. The book also supposedly shows a photo of "Latrodectus lilianae" to accompany this section, which is actually a photo of an adult female Latrodectus tredecimguttatus.

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 also turned up on occasions, as accidental imports hidden amidst other imported goods, particularly cars. The three species of Black Widow found in the USA, where most imported cars carrying accidentally imported Latrodectus species are imported from, include the Western Black Widows, Latrodectus hesperus, the Southern Black Widow, Latrodectus mactans, and the Northern Black Widow, Latrodectus variolus, are not regarded as invasive species and do not adapt well to climatic variations. It is unlikely that any of these would successfully establish breeding colonies in the UK's damp climate. In fact Black Widows in some countries are reported to be on the decline due to the invasive and highly adaptable Brown Widow, Latrodectus geometricus, which is expanding its range in many parts of the world. I would expect Steatoda nobilis to easily outcompete any Black Widows if they were to establish a colony anywhere in the UK. My research has lead me to find the following examples of Latrodectus species that have been discovered in the UK:

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 hesperus, 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 hesperus 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 hesperus, 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 hesperus.

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 15/05/2021 a dead adult female Brown Widow & her egg-sacs were found in Newark, Nottinghamshire, amongst Red Grapes, imported from South Africa, and purchased from Morrisons. LINK

9) On 08/04/2021 a black spider ,with a red dot on its abdomen, was found in a garden in Buckinghamshire. It was not possible to tell for sure if it was a female Steatoda paykulliana or a Latrodectus species. LINK

10) On 21/07/2022 an adult female Brown Widow was found on the outside of a shipping container at Southampton Docks, in Hampshire. It's believed the container originated from Vietnam. LINK

11) On 22/08/22 two adult female Western Black Widows, Latrodectus hesperus, were found in Southport, Merseyside, living in a car that had recently been imported from Arizona, USA. They were able to survive here due to the long, hot summer of 2022. Latrodectus hesperus is a species typically associated with dry, desert-like conditions in the USA and there is no chance of this species being able to survive the cold, damp climate of the UK throughout much of the year. LINK LINK 2

12) On 13/01/2020 an adult female Brown Widow, Latrodectus Geometricus, & egg-sac were found in Black Grapes, purchased from Asda in Cwmbran, South Wales. The grapes had been imported from Brazil. LINK

13) In August 2015 an adult female Black Widow, either Latrodectus mactans or Latrodectus hesperus, was found living beneath a VW Camper Van in Pershore, Worcestershire. The campervan had recently been taken out of storage following its importation to the UK from California, USA. LINK

14) 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.

15) On 30th October 2015 an adult female Black Widow was found in Uckfield, East Sussex, on a truck that had recently been imported from Arizona, USA. The spider was taken into captivity. LINK

16) On 25th April 2023 a Latrodectus sp., probably Latrodectus geometricus, was found in red grapes, being sold on a market stall outside Queen Elizabeth Hospital, in Birmingham. The spider was already dead when discovered. LINK

17) On 1th September 2018 - Gloucestershirelive.co.uk reported claims of around 100 Redback Spiders, Latrodectus hasselti, being found on a large piece of electrical equipment in Northway, Tewkesbury, Gloucestershire. The equipment was brought over from New South Wales, in Australia, to be serviced in Britain, when the spiders were discovered and pest control services were called. LINK

18) On 3rd August 2023 a Black Widow spider was found alive in its web in the engine bay of a recently imported Chevrolet pickup truck from California, USA to Banbury, Oxfordshire, in the UK. The spider was easy to identify as the Western Black Widow, Latrodectus hesperus. Latrodectus hesperus is the only Latrodectus species found in California, apart from the Brown Widow, Latrodectus geometricus. LINK

On 21st August 2023 Dmitri Logunov, an expert in the field of arachnid identification at the Manchester Museum, was very helpful in providing me with the following three records that the Manchester Museum have of Latrodectus species arriving in the UK with imported goods. All three Latrodectus specimens were formally identified by the museum and now form part of their arachnid collections.

19) On 16th November 2011 a live female Latrodectus geometricus was found in a skip containing cardboard packaging. It arrived in the UK hidden amidst imported Saytex Fire Safety equipment, which had been stored at both Magnolia, Arkansas, and Dallas, Texas, in the USA.

20) On 14th November 2007 a female Latrodectus variolus arrived in West Yorkshire hidden amidst imported grapes from California, USA.

21) During the summer of 2003 an unidentified juvenile female Latrodectus specimen was donated to the museum after it arrived in the UK in a car tyre that had been imported from California, USA.

22) On the 17th June 2011 the BBC reported on an adult female Black Widow spider being found at Chatham Dockyard, in Kent, amidst imported cars. The spider was taken away to a local vet in Maidstone, who passed the spider onto London Zoo. The spider went on to produce an egg-sac. The BBC's article was full of misinformation, such as claiming that male Black Widows are not venomous, which they are. Kent Online reported the story more accurately.

23) On 19th October 2023 at least two adult female Western Black Widows, Latrodectus hesperus, spiderlings and egg-sacs, were found in North Wales on an imported car from Arizona, California, USA. The car came with paperwork to prove it had been fumigated with pesticide gas before being transported, The owner of the car had been driving the car for two months in the UK, and it was only when the car was being worked on that the spiders were discovered. - LINK LINK 2

24) On 4th December 2023 a 10mm dead adult female Brown Widow, Latrodectus geometricus, was found in a fruit bowl. Closer inspection revealed webbing on the white grapes that had been bought from the Hersham branch of Lidl's, in Surrey. The grapes were imported from Peru. - LINK

25) On 9th December 2023 a dead adult female Brown Widow, Latrodectus geometricus, was found with webbing amidst red grapes purchased from Sainsbury's in Broadstairs, Kent, that were imported from Peru. - LINK

26) On 5th January 2024 a dead adult female Brown Widow, Latrodectus geometricus, was found amidst imported white grapes from Peru. The grapes were purchased from a Co-op store in Stockport, Greater Manchester. - LINK

27) On 7th January 2024 a dead adult female Brown Widow, Latrodectus geometricus, was found amidst imported red grapes from Brazil. The grapes were purchased from a Lidl store in Bournemouth, Dorset. - LINK

28) On 23rd January 2024 a dead adult female Brown Widow, Latrodectus geometricus, was found in white grapes imported from South Africa. The grapes were purchased in Bolton, Lancashire. - LINK

29) On the 24th January 2024 a dead adult female Brown Widow, Latrodectus geometricus, was found in red grapes purchased from Asda in Duffryn, Newport, South Wales. - LINK

30) On the 25th January 2024 a dead adult female Brown Widow, Latrodectus geometricus, was found in imported red & green mixed grapes delivered from Shrewsbury. - LINK

31) On the 28th October 2024 a live adult female Black Widow was found living in a trunk at the bottom of a residential garden in Cambridge after the occupier recently imported goods from Nevada USA. Only two Latrodectus species are found in Nevada, the Western Black Widow, Latrodectus hesperus, and the Brown Widow, Latrodectus geometricus. This, along with the hourglass marking, made it easy to identify the spider as a Western Black Widow. - LINK

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

* I'd like to give grateful thanks to Elaine Cameron for kindly sending this dead specimen to me so it could be photographed and have its identity confirmed. *

Deceased 10mm adult female Brown Widow, Latrodectus geometricus, accidentally imported with white grapes from Peru, South America, 4th December 2023

* I'd like to give grateful thanks to Brenox Mac Cionnaith, and his sister, for kindly sending this dead specimen to me so it could be photographed and have its identity confirmed. *

Deceased 10mm adult female Brown Widow, Latrodectus geometricus, accidentally imported with white grapes from Peru, South America, 4th December 2023

This close up image of the adult female Latrodectus geometricus shows orange hourglass marking, indicative of Latrodectus geometricus, rather than the ruby red hourglass marking found on many other Latrodectus species. The hourglass marking of Latrodectus geometricus, can very occasionally also be found in red, yellow or even grey though.

Deceased 10mm adult female Brown Widow, Latrodectus geometricus, accidentally imported with white grapes from Peru, South America, 4th December 2023

This close up image of the adult female Latrodectus geometricus shows the eye-arrangement and the key spacing of the outer pairs of eyes that identify the spider as Latrodectus species rather than Steatoda species.

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

31) 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. Latrodectus elegans also produce spiky egg-sacs, but Latrodectus elegans are an Asian species not found on the South American continent. 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 is common for the Brown Widow to create several egg-sacs at a time, some times 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 / Geometric Button Spider / Brown Button Spider (Latrodectus geometricus)

The Brown Widow was originally discovered in South America, although many sources claim that the species originated from southern Africa. The Brown Widow's range now covers many pantropical and subtropical areas around the world. Although this species does turn up in the UK very 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, typical of Latrodectus species, on its underside. However, instead of it being bright red, as with most of its Black Widow cousins, the Brown Widow's 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 usually medically significant, probably due to the low volume of α-latrotoxin delivered during a bite. 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 has long been suspected as being responsible for displacing some Black Widow species in their native countries. In a recent study, published in January 2023, it was confirmed that the Brown Widow, Latrodectus geometricus, is definitely displacing Florida’s Southern Black Widow, Latrodectus mactans, and California’s Western Black Widow, Latrodectus Hesperus. The studies revealed that Brown Widows have twice the fertility potential as Southern Black Widows. In experiments comparing development, it was shown that sub-adult Brown Widows grew faster and matured earlier, relative to Southern Black Widows. The Brown Widow doe not just predate the Black Widow because of prey scarcity, but the bold Brown Widow actively hunts the shy Black Widow, preferring it to other spider species as prey.

LINK LINK 2 LINK 3

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 towards humans 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 usually poses no risk to humans at all as its fangs are too small to penetrate most human skin.

Latrodectus geometricus produce very distinctive spiky egg-sacs. The only other Latrodectus egg-sac, that I'm aware of, that can sometimes be mistaken is the slightly spiky egg-sac of the Asian Black Widow species, Latrodectus elegans. Research published in 2019 proved that the egg-sacs of Latrodectus geometricus have antibacterial properties that protect the eggs within from bacteria or fungal growth. - LINK

One Latrodectus geometricus egg-sac can contain as many as 120-150 eggs. Fertilised 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. Most other species of Black Widow do not produce 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 is common. 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 observed with 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 LINK 6 BITE

The Brown Widow, Latrodectus geometricus, was originally believed to be present in Madagascar too. Further analysis of the Brown Widow in Madagascar revealed it to be distinctive enough to be classed as a comletely separate species, Latrodectus obscurior. Latrodectus obscurior is also found in Cape Verde too, an Island country off the west coast of Africa. Latrodectus menavodi, the Madagascan Black Widow, is the second Latrodectus species to be found in Madagascar.

Is the Brown Widow found in Europe?

Yes, the spread of the Brown Widow has now reached Europe, and Latrodectus geometricus is established in both Cyprus and Turkey. In Duncan McCowan's 2014 book "60 Cypriot Spiders" the Brown Widow was already referred to as the most common Latrodectus species in Cyprus. The author also claimed Latrodectus geometricus had been well established for years around a play area at Larnaca's tourist beach. Latrodectus geometricus was officially listed in the "Spiders of Cyprus" catalogue in 2019. LINK

In 2023 I was able to personally confirm for myself that Latrodectus geometricus is now widely established, and extremely common, in Cyprus.

For further information on the spread of the introduced Latrodectus geometricus in Europe visit this page of my website - The Brown in Cyprus

Could supermarkets be using Widow Spiders as a form of biological pest control?

With Latrodectus specimens, especially dead specimens, being found fairly regularly as accidental stowaways, hidden amidst imported fruit, supermarkets have in the past been accused of using Widow Spiders as a form of biological pest control within their crops. This is something that supermarkets have always strongly denied, but is there any truth to these rumours? In my opinion the idea that any supermarket would deliberately encourage or even introduce highly venomous species within their crops is quite frankly absurd. Crops are often protected by deliberately introduced biological control species, including spiders, but the species used are always harmless to humans.

Crops such as grapes are often picked in their home countries by hand. I don't believe the farmers of these crops would risk the health and lives of their workers by introducing such hazards to their vineyards deliberately. I also believe there is no chance that Supermarkets would ever risk their UK customers finding a highly venomous species within their produce, for risk of being sued. Measures are taken to prevent non-native species from reaching the UK within imported fruit and veg. Produce is regularly treated with toxic pesticides, and any invertebrate hitchhikers that manage to survive the pesticides usually die during the refrigerated transport of the produce as it travels to the UK. The BBC covered the story back in 2002. - BBC News - "Tesco Denies Using Deadly Spiders"

In 2013 the story surfaced again, this time written by 'Modern Farmer'. The article implied that Tesco had admitted to using Latrodectus species as a form of biological pest control in their vineyards. I'm afraid I don't believe a word of that article though. There are no dates or details to support any of their claims, so they can't be validated. Any article written about Latrodectus species, that uses a photo of a tarantula on their grapes, is off to a very bad start unfortunately. Just the terminology used throughout the article stinks of scaremongering and sensationalism. I suspect their supposed quote from Tesco has also been deliberately taken completely out of context as well. Even the article itself reports that Latrodectus species would be a very inefficient form of biological pest control in grape vineyards, so it makes little sense for farmers use them. - modernfarmer.com

Are Black Widows Venomous or Poisonous?

The term "poisonous" is generally 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? In most cases yes, but not always. 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, due to the toxins these species carry. 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 eggs 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

These toxins present in Black Widows certainly don't deter all invertebrate predators. The Brown Widow actively hunts Black Widow spiders. Even the much smaller Candy-Stripe Spider has been recorded invading the webs of Black Widows and feeding on their spiderlings. LINK

Dangerous Wild Animal Act Species

In the UK there are only four genus of spider that fall under the Dangerous Wild Animals Act 1976. These include the certain types of Wandering Spiders (Phoneutria genus), the Sydney Funnel-web Spider (Atrax genus), the Recluse Spiders (Loxosceles genus) and the Widow Spiders (Latrodectus genus). All other species of spider are not considered by UK Law to have a bite significantly dangerous to humans and can therefore be kept in captivity without restrictions.

A DWAA licence needs to be obtained from the local council to keep DWAA species at any premises for longer than a 72 hour continuous period. A DWAA licence is not required to collect or transport DWAA species to a licence holder.

Black Widow further information:

Widow Spiders in the Americas - LINK LINK 2

List of Latrodectus species - LINK LINK 2

Further reading: National Library of Medicine - A review of Latrodectus species,

Widowman - Widow Spiders in the USA

Distinguishing between Latrodectus and Steatoda species.

Eye arrangements of Latrodectus and Steatoda species.

Sometimes it can be very difficult to distinguish between a dark, unmarked Steatoda specimen and a Latrodectus specimen. The two can be reliably separated by taking a close look at the eye arrangements. Spiders of both Steatoda and Latrodectus genus have eight eyes, and the arrangements of both are very similar. However, there is a distinctive difference when we look at the outside pairs of eyes, the posterior lateral eyes and the anterior lateral eyes. On Latrodectus species there is an obvious gap between the PL eyes and the AL eyes. However, when we look at the eyes of all Steatoda species we find that the PL eyes are touching, or very nearly touching, the AL eyes. In many cases the PL eyes are actually fused together with the AL eyes.

The abdomen is one helpful indicator that may help to distinguish between the two genus without getting too close to the spiders. Generally Latrodectus species have a taller, narrower, and more teardrop-shaped abdomen than that of Steatoda species, and the abdomen tends to be more pointed towards the rear end. The legs are another helpful indicator when trying to identify the genus from a photo. Latrodectus species typically have proportionally longer legs when compared to those of Latrodectus species. If egg-sacs are present then this helps considerably to identify the genus. The egg-sacs of Steatoda species tend to have a more fluffy appearance than most Latrodectus species.

There is also another way to distinguish between Steatoda sp. and Latrodectus sp. but it requires microscopic examination of the chelicerae. The chelicerae of Steatoda sp. usually have one or two tiny teeth near the base of the fangs. Many Steatoda species exhibit one tooth on the male and two smaller teeth on the female. Latrodectus species do not possess these cheliceral teeth.

When researching this information in March 2023 there were plenty of sources that seem to contradict this information regarding Steatoda nobilis though. Some sources claim that both male and female Steatoda nobilis have no cheliceral teeth, whilst other sources claim that both sexes of Steatoda nobilis have one cheliceral tooth. Even experienced arachnologists couldn't agree on this matter. Hopefully future microscopic study of the chelicerae of Steatoda nobilis specimens will confirm the reliability of using this method to distinguish Steatoda nobilis from Latrodectus sp.

Eye arrangements of Latrodectus geometricus and Steatoda paykulliana.

BLACK WIDOW / TRUE WIDOW SPECIES THROUGHOUT THE WORLD

Kingdom: Animalia
Phylum: Arthropoda
Class: Arachnida
Order: Araneae
Family: Theridiidae

Sub-family: Latrodectinae

Genus: Latrodectus

1. Latrodectus antheratus - Black Widow - (Paraguay, Argentina)

2. Latrodectus apicalis - Galapagos Black Widow - (Galapagos Islands)

3. Latrodectus bishopi - Red Widow - (Florida, USA)

4. Latrodectus cinctus - African Black Widow / Black Button Spider - (southern Africa, Cape Verde and Kuwait)

5. Latrodectus corallinus - South American Black Widow - (Argentina)

6. Latrodectus curacaviensis - South American Black Widow / Brazilian Black Widow - (South America)

7. Latrodectus dahli - Dahl's Widow - (Morocco, to Central Asia, Saudi Arabia, Israel, Greece & Cyprus)

8. Latrodectus diaguita - (Argentina)

9. Latrodectus elegans - (East Asia, China & Japan)

10. Latrodectus erythromelas - (Sri Lanka)

11. Latrodectus garbae - (Dry forests of Colombia) New Species

12. Latrodectus geometricus - Brown Widow / Geometric Brown Button Spider - (Africa, with introductions to the Americas, Poland, the Middle East, Pakistan, India, Thailand, Japan, China, Papua New Guinea, Australia, Cyprus and Hawaii)

13. Latrodectus hasselti - Redback Spider / Australian Black Widow - (Australia, introduced to Japan)

14. Latrodectus hesperus - Western Black Widow - (Western USA, Mexico, Western Canada)

15. Latrodectus hurtadoi - (Dry forests of Colombia) New Species

16. Latrodectus hystrix - (Yemen, Socotra)

17. Latrodectus indistinctus - Black Button Spider - (South Africa)

18. Latrodectus karrooensis - Black Button Spider - (South Africa)

19. Latrodectus katipo - Katipo or Red Katipo Spider - (New Zealand)

20. Latrodectus lilianae - Moroccan Black Widow Spider - (Iberian Peninsula, Portugal, Spain & Morocco)

21. Latrodectus mactans - Southern Black Widow - (USA)

22. Latrodectus menavodi - Madagascan Black Widow - (Madagascar)

23. Latrodectus mirabilis - (South America)

24. Latrodectus obscurior - (Cape Verde and Madagascar)

25. Latrodectus occidentalis - (Mexico)

26. Latrodectus pallidus - White Widow - (Middle East, Central Asia & North Africa)

27. Latrodectus quartus - (Argentina)

28. Latrodectus renivulvatus - (Africa, Saudi Arabia and Yemen)

29. Latrodectus revivensis - Black Button Spider - (Israel, Palestine)

30. Latrodectus rhodesiensis - Brown Button Spider - (Zimbabwe)

31. Latrodectus thoracicus - (Chile)

32. Latrodectus tredecimguttatus - European Widow / Mediterranean Widow - (Mediterranean Area)

33. Latrodectus umbukwane - Phinda button spider - (Zululand, KwaZulu-Natal, South Africa) New species 2019

34. Latrodectus variegatus - (Chile, Argentina)

35. Latrodectus variolus - (USA, Canada)