This is a spider that when you see it you wonder what it is. They pack quite a nip so be careful if you come across it but if you have its prey around your damp areas of your home they are good to have around.
The woodlouse spider (Dysdera crocata) is a species of spider that preys exclusively upon woodlice. Other common names refer to variations on the common name of its prey. These are woodlouse hunter, sowbug hunter, sowbug killer, pillbug hunter and slater spider.
Appearance
Female specimens are 11–15 mm long while males are 9–10 mm. They have a dark-red cephalothorax and legs, and a shiny (sometimes very shiny) yellow-brown abdomen. Notably, they have disproportionately large chelicerae. Dysdera crocata is difficult to distinguish from the much less common Dysdera erythrina though this species is not often found near human habitation.
Behavior
They are usually to be found under logs in warm places, often close to woodlice. They have been found in houses. They spend the day in a silken retreat and hunt at night without the use of a web. Their diet consists exclusively of woodlice which—despite their tough exoskeleton—are pierced easily by the spider's large chelicerae.
The courtship of these spiders is typically aggressive and mates risk injury from each other's large chelicerae. The female lays her eggs in a silken sac and is believed to look after her young after hatching like the "Mothercare" spider (Theridion sisyphium).
They have been known to bite humans if handled. Their bite can be painful but the venom causes no major medical problems. Localised itchiness at the bite site has been reported in some cases.