What is "woodlouse spider"

n. a European spider, ''Dysdera crocata'', that has been introduced to the United States; it has a painful, but not normally dangerous, bite

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, including woodlouse hunter, sowbug hunter, sowbug killer, pillbug hunter and slater spider.