SPIDERS!

Woman nearly lost arm after black widow spider bite

‘I nearly lost my hand to Britain’s most poisonous spider’

Venomous spiders found in Swindon family’s home

Spiders can quite unnecessarily evoke all kinds of dread and fear. The Press does not help by publishing inaccurate and often alarmist stories about them. All the above are examples of recent headlines, and the attached stories often fail to report the fact correctly, or even have evidence of what spider actually caused the bite. Spiders are in fact one of our most important beneficial creatures – spiders in the UK devour a weight of insect ‘pests’ equivalent to that of the nation’s human population.

However, we do understand that spiders can upset many people, and this is borne out by the dozens of phone calls we receive at the Booth each week at this time of year. To help keep people informed we are publishing this edited article on False Black Widows taken from the fact sheet written by our recently retired entomologist and Keeper of the Booth Museum, Dr Gerald Legg.

Steatoda nobilis (wikimedia commons)
Steatoda nobilis (wikimedia commons)

During the mid-late summer, many spiders mature and as a result become more obvious as they have grown to their full size. One of these species is Steatoda nobilis. It came from the Canary Islands, and was first recorded in Britain near Torquay in 1879. However it was not described from Britain until 1993, when it was known to have occurred since at least 1986 and 1989 as flourishing populations in Portsmouth (Hampshire) and Swanage (Dorset). There was also a population in Westcliff-on-Sea (Essex) recorded in 1990, and another in Littlehampton and Worthing (West Sussex). Its distribution is spreading more widely along the coast in the south and also inland, with confirmed records from South Devon, East Sussex, Kent, Surrey and Warwick. The large, grape-like individuals are the females and the smaller, more elongate ones, the males.

These spiders are have become known as False Widows and, because of their colour, shape and size, are frequently mistaken for the Black Widow Spider that are found in warmer climes, but not in Britain (although some occasionally come into the country in packaged fruit and flowers).

Black Widow with its distinctive red markings (wikimedia commons)
Black Widow with its distinctive red markings (wikimedia commons)

Black Widow Spiders belong to the world-wide genus Latrodectus. They have a nasty bite and do occasionally kill. These are found around the world, including southern Europe, southern USA and Mexico, the Middle East and Australia (Latrodectus mactans). They can easily be distinguished from the False Black Widows by the presence of bright red markings on their abdomen (tail). The deadly Red Back Spider also has this red warning mark on its back, whilst the Australian Funnel Web spider looks very different from the False Black Widow. In fact, out of approximately 40,000 known species of spider only around 200 are known to have serious bites, and none are found in the UK.

The False Widow spider, Steatoda nobilis spins a tangled web like other members of the Theridiidae family, which are know as ‘Button Spiders’. In the UK two species are commonly mistaken for Black Widow spiders. They are Steatoda bipunctata, or the Rabbit Hutch Spider, and the one that most resembles the Black Widow species, Steatoda grossa.

Steatoda bipunctata (wikimedia commons)
Steatoda bipunctata (wikimedia commons)

Steatoda nobilis has a distinctive pattern of pale markings on its brown abdomen. Females grow to 15mm. It is closely related to the widespread and common spider of houses and outhouses, Steatoda bipunctata, but this species has little patterning, with a whitish line around the front of the abdomen and sometimes a line down the middle of it. Both sexes of S. nobilis are also larger than those of S. bipunctata. S. nobilis is the one most likely to cause a bad reaction if it bites.

Steatoda grossa lives in houses, in walls, fences and the bark of trees. They eat insects, other invertebrates, and even other spiders. They can also be found behind stacked timber, in conservatories, sheds, under window-sills, in garages and even indoors. Favourable weather, particularly the mild winters of late (2004-2008), have favoured the spread of these spiders.

However, the likelihood of being bitten by a False wWdow spider is extremely low; the spider prefers to stay hidden in its web. Most importantly, no one has ever died of a spider bite in the UK and the number of reported bites from spiders is small.

The spider most likely to be seen in a house, especially at night, and the one most likely to be in the bath is the House Spider, Tegenaria domestica. They don’t fall into the bath but climb down for a drink of water at the plug-hole. The slippery sides of the bath prevent them from getting out again. Leave a towel draped over the edge of the bath for them to use to escape then you will not see any in the bath. They, together with the other spider residents, eat a lot of pest insects which also share your home and so pay rent for their keep.

Around 35,000 species of spiders occur worldwide. As predators they, like snakes, use venom to subdue or kill their prey. However, the venom of most species has little or no effect on people and most are not interested in biting nor can their jaws puncture human skin. Most people are unlikely to come into contact with many of the species.

There are two basic types of venom which may or may not be combined together. These are neurotoxic venom (that affects the nervous system) and necrotic venom (that dissolves the tissues).

There are over 640 species of spider in Britain, and only a dozen of these have been known to bite humans. These include the two Steatoda species. The severity of symptoms from any spider bite depends on the amount of venom that is injected. Symptoms from the bites of most of these are similar, with local pain and swelling, and are certainly no worse than those from a bee or wasp sting. If allergic to the venom, in some cases the pain can become more intense and start radiating, and other symptoms may follow, including sweating (indicating parasympathetic stimulation) and feverishness. False Widow Spider bite reports include symptoms such as chest pains, and swelling and tingling of fingers. Should any severe symptoms occur it is recommend that medical advice be sought and it is important to stress the fact they you have been bitten. Ideally keep the spider as evidence.

What should I do if I am bitten?

1. Wash the bite with soap and water.

2. Apply a cool compress/ice-pack (take care not to cause a cold burn; don’t leave on for more than a few minutes at a time).

3. If possible apply a bite spray such as ‘Waspeze’.

4. If necessary, take over-the-counter medication to control pain or itching (e.g. antihistamine cream and suitable painkiller).

5. Antibiotics are not helpful unless the wound becomes infected.

6. Do not cut or apply suction to the wound.

7. Monitor the bite for redness, swelling, pain, or signs of infection.

8. Monitor breathing, sweating and general demeanour.

8. Re-apply ‘Waspeze’ to control bite symptoms and promote healing.

9. If redness, swelling or pain does not subside or there are signs of infection consult your doctor.

What should you do if you find any False Widow spiders, or any others for that matter? Not a lot! If they are outside, it is impossible to eradicate them as there are just too many of them and, if you were to kill those in your garden others would come in to fill the niche.

Indoors it is a different matter as they can be controlled simply by vacuuming them up. Some commercial sprays from garden centres, hardware shops do work, but not very well because the spiders can hide in their webs. Areas beneath beds, behind settees and curtains, and under cupboards are the places they are likely to occur if they do find their way indoors. You can also remove them using thick gardening gloves or a glass and paper. Please do not panic, and treat them as you would a wasp or bee in your home.

Gerald Legg, Retired Keeper of Natural Science.

Edited by Lee Ismail, Curator of Natural Sciences

One Response

  1. I am very glad to see an article that sheds a positive light on spiders. I am fond of spiders and like to photograph any I encounter on my travels but a lot of people have an instinctive fear of them. I use the word “instinctive” advisedly as I believe many people have an irrational fear of spiders that is beyond their rational control.

    I think it is very important for experts such as yourself to conduct educational exercises like this one to instill a sense of reality in people’s minds. I had a falling out with the zoo on the Isle of Wight which called its section on insects etc. “Nature’s Nightmares”, helping perpetuate the prejudice against them. For a zoo to do that I felt was unforgivable. (I think they subsequently changed the name.)

    When spiders come indoors, I usually just pick them up in my cupped hands and deposit them outside. Anyone who doesn’t want to do that only needs a transparent plastic box of the sort sold with so many products, and a piece of card. Trap the spider under the box, slide this gently over the card and take the trapped spider outside. What could be simpler?

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