There are currently around 670 different species of spider occurring in Britain. Of the spiders commonly found in houses or gardens, quite a few are patterned or dark in appearance, and Zygiella x-notata, Metellina species, Amaurobius species and Araneus diadematus garden spiders are frequently being mistaken for possible ‘false widow’ spiders and repeatedly wrongly reported in the media as poisonous.
There are a number of Steatoda species found in Britain, all so-called ‘false widow’ spiders. Three are possible in or near buildings. These include S. bipunctata (very widespread, probably occurring in every house, outhouse and building in the country, completely harmless to humans), S. grossa (widespread and sometimes very frequent in the southwest, but becomes much scarcer further north and east, but in the last few years seems to be increasing), and S. nobilis, the one which gets the press for biting humans (originally confined to the south coast, now increasingly turning up elsewhere in southern England). S. nobilis has on occasions been responsible for bites, and S. grossa is also known to be able to pierce human skin, even though many of the cases publicized for this are almost certainly due to another cause. There are a few other species of spider in Britain also capable of piercing human skin. Unlike S. bipunctata and S. grossa, which are native to this country, S. nobilis is thought to have been introduced to the UK and was first recorded at Torquay in 1879; so it’s been here a long time.
The media hype about ‘false widows’, by which presumably S. nobilis is meant, is beyond any reason and irresponsible. S. nobilis is widespread and numerous along much of the south coast, has been established in the Southend area of Essex since at least 1990, and in more recent years has spread widely and become much more numerous in England as far north as Norfolk and also south Wales. Everybody in the coastal counties of Southern England has had lots of them in their house and garden for many years, whether they have been aware of this or not. They are now one of our commonest southern house and garden spiders. The fact that harm caused by them is extremely rare should tell you something about how dangerous they really are …
More information on spiders is available from the British Arachnological Society.