7 March 2012

Poisonous spiders in the UK? That's got to be false!

Everyone knows that the only dangerous poisonous animal on the British Isles is the common adder, Vipera berus, right? Wrong. For over a century now, a relative of the infamous black widow spider known as the false widow, has been an unwelcome guest on our shores. Up until now however, it has been restricted to the south of Britain where it is warm enough for the spider to survive through the winter, but increasingly mild winters have allowed it to advance further northwards and it has recently been spotted in Bristol, Berkshire and Norfolk.

The spider belongs to the genus Steatoda and is relatively small, being no bigger than a 5p piece. False widows get their name because they look very similar to black widows, mainly due to the shape of their body. However, they are no where near as poisonous and deaths resulting from their bite are rare, usually only because the individual goes into anaphylactic shock like with bee stings. Although this doesn't mean that its bite is harmless, as it injects enough venom in every bite to cause severe pain and inflammation. The pain is intense enough for doctors to have given its own unique name: steatodism.

The small false widow spider on the top of a man's hand. Notice the white ring around the edge of its abdomen, which can be used to identify the spider.

Fortunately bites from false widows are rare, meaning that until recently, their presence in the UK has been unknown by most of the population. However, this is beginning to change after a man collapsed in a toy store after being bitten ten times on the neck by the spider, which is believed to have dropped into his hood. He collapsed within moments, feeling light headed, hot and began to gag. An ambulance was called and the man was rushed to Southampton General Hospital, where he was treated and kept in overnight. Luckily, long term damage from false widow bites is uncommon and he has made a full recovery, simply saying that he was "just thankful that it never jumped out and got onto my [the man's] daughter".

Our milder winters mean that the false widow is likely to spread through more of the UK, meaning that many more of us are likely to come into contact with it. Despite this, there is no cause for concern since bites from the spider are rare. Only a handful have ever been reported in the UK and none have ever resulted in a death. Like most wild animals, the spider will only bite a human in self-defence if it feels threatened; so, as long it is left alone, there's no cause for concern.

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