Yellow sac spider

Yellow sac spider is a common name for spiders in the genus Cheiracanthium, especially the North American species Cheiracanthium inclusum.

Yellow sac spider is a common name for spiders in the genus Cheiracanthium, especially the North American species Cheiracanthium inclusum. These small, pale spiders are nocturnal hunters that build silk retreats rather than capture webs, and they may bite if pressed against skin. Their bites are usually painful and irritating but are generally not considered dangerous to most people.

Taxonomy and naming

Yellow sac spider is a common name applied mainly to spiders in the genus Cheiracanthium. The genus was first described in 1839, and species in it have been placed in different families historically, but are now classified in Cheiracanthiidae.

Appearance and behaviour

These spiders are typically small, pale yellow or yellow-green, with a slightly shiny look. They are nocturnal predators that actively hunt and use small silk-lined sacs or retreats for daytime shelter rather than for web-based prey capture.

Distribution and habitat

Yellow sac spiders are widely distributed across the Americas, including much of the United States and parts of southern Canada. They are often found outdoors in vegetation, gardens, bark, rocks, and sheltered crevices, but may also enter houses.

Bites and medical importance

Yellow sac spiders are venomous, and bites can cause pain, redness, swelling, or a stinging sensation. They are sometimes described as medically significant because some bites can produce more serious local effects, but most are not dangerous to humans.