False Widow Spider

False Widow spider London

Recently there has been a surge of sightings of false widow spiders. I caught a glimpse of this one on the ground whilst I was cycling by the Thames. It was large enough and dark enough to catch my attention from my bike. It was a beautiful false widow spider of the species Steatoda grossa. 

The legs are black, the abdomen is a rich deep brown with pale triangular markings on the top (just visible in the photograph, click on the picture to enlarge it). The species gets it’s name from visual similarities with the notorious Black Widow. The Black Widow is found in southern Europe, southern USA and Mexico, the Middle East and Australia. They are not found in the UK.

False Widow spiders can bite if provoked, but their bite is much less severe than that of their feared cousin the Black Widow. A False Widow spider bite reportedly feels like a bee sting, however symptoms can include chest pains, swelling and tingling of fingers. As with all spider bites, the severity of the bite depends on the amount of poison injected.

There are six different species of False Widow in the UK, Steatoda grossa is a native UK species. The species hitting the news headlines at the moment is Steatoda nobilis, or the Nobel False Widow. This species is not native, it arrived in the UK around 100 years ago, and it’s distribution is spreading.

Most spiders produce venom in order to subdue their prey, but only a few are powerful enough to pierce human skin. There are 640 species of spider in the UK. Only 12 of these have been known to bite humans in the UK, and this includes False Widow Spiders (Natural History Museum 2007). However bites are rare, the Natural Museum states the following about Steatoda nobilis:

‘is probably the UK’s most venomous spider but bites are rare and usually result from handling the spider roughly or from a spider being trapped between clothing and skin’.

 At this time of year False Widows, like many invertebrates, often take refuge from the cold weather by entering buildings. They will generally set up home in a warm spot, such as behind a washing machine, and will go about their business of catching flies unnoticed by humans eyes, and do no harm whatsoever.  If you see a False Widow there is no need to harm it. You may wish to safely remove it from your house by catching it a cup. If possible place the spider outdoors near to some form of shelter; a woodpile or similar.

To be on the safe side, admire this beauty with your eyes and not your fingers.