Yellow Sac Spiders (Ceiracanthium inclusum)
The yellow sac spider is common throughout the eastern United States, in particular from New England through the Midwest. It is normally an outdoor spider but will readily enter and breed inside homes and other buildings. The silken “sac” retreats are usually seen in corners along baseboards, along the ceiling, and beneath and behind furniture. Outdoors, the sacs will be found beneath the bark of trees and under items such as stones and logs. Sacs may also be found along soffits, beneath window sills and around door frames.
Belongs to a family of spiders known for resting in a small silken retreat or sac during the day. The yellow sac spider is a nighttime hunter that feeds on small insects and possibly even other spiders. As they wander about in search of prey, they sometimes crawl onto people sitting on a couch or lying in bed. The spider may then bite the person one or more times. The yellow sac spider likely accounts for more bites on people than any spider in the United States. Fortunately, the venom of this spider produces minimal effects.