The woodlouse spider (Dysdera crocata) is instantly recognisable with its red head, thorax and legs combined with a pale oblong body. Ranging from 10 to 15mm in length this spider has no hair and a shiny appearance. The other identifying feature of the woodlouse spider are the large, immediately visible fangs that project directly forward from the head. In my opinion this is one of the scariest looking of all the British spiders!
Dysdera is known by several names all of which relate to its exclusive diet of woodlice; sowbug hunter, sowbug killer, woodlouse hunter, pillbug hunter and slater spider are all alternate common names.
As woodlice have a tough, protective exoskeleton the woodlouse spider needs to be equipped with strong, large fangs or chelicerae – which it is. Not only are these fangs capable of piercing human skin, they also present somewhat of a problem during the aggressive courtship behaviour of the spiders!
On the rare occasions that people have been bitten by Dysdera the degree of pain has been described as ranging from a nettle sting to a bee sting. The venom is not thought to be particularly significant to humans but local itchiness and marking has been reported.
Although widely distributed across the UK there is less chance of coming across a woodlouse spider as they live outdoors and are nocturnal. They spend the daytime hiding in a silken retreat in crevices or often under logs.