I live in Toronto, Ontario. I found this bug crawling on my basement floor...

Asked November 10, 2013, 10:05 PM EST

I live in Toronto, Ontario. I found this bug crawling on my basement floor (the basement is finished). It has 10 legs so it doesn't appear to be a spider, but I am wondering if it is something to be concerned about. It was very large (about 1 - 1 1/2 inches long and fairly wide). The photo is pretty much to scale. It had a large grey bum and a reddish brown thorax, with brighter red legs. I appreciate your help.

Outside United States insect identification

1 Response

The "bug" in your photo and basement is indeed a spider, specifically the "woodlouse spider" (scientific name: Dysdera crocata (Araneae: Dysderidae)). This species was originally native to Europe, but has moved around with humans and now is found in many parts of the world, including the eastern U.S. and Canada. As its name implies, it feeds almost exclusively on woodlice, sowbugs, pillbugs, and their relatives. It actually does have only 8 legs, but there are two shorter "leg-like" appendages at the front end of spiders called pedipalps that are used for handling prey. This spider is also notable for its very large protruding jaws (chelicerae) which help it bite through the tough shells of the woodlice. This spider is normally found outdoors in the woods in leaf litter and rotting logs where its prey also live. They are occasionally found in houses, especially basements into which sowbugs and pillbugs also may enter. The bite of this spider may be painful, but is not considered poisonous. If you look up "woodlouse spider" on the web, you will find photos and more information about this spider.