Diagnostic characters
- Pale yellow, cream, or light green body with no distinct pattern
- Darker chelicerae contrasting with the pale carapace
- First pair of legs noticeably longer than the others
- Silken retreat sac in a wall-ceiling junction or folded leaf
- Roams walls and ceilings after dark
Habitat and seasonality
Interior wall and ceiling corners, behind picture frames and curtains, under siding, and in foliage and leaf litter outdoors.
Indoors year-round. Outdoor populations move into structures in autumn as temperatures fall.
Medical significance
Low to moderate. Bites produce immediate sharp pain, erythema, and occasionally a slow-healing lesion, but claims of true dermonecrosis are not supported by controlled evidence.
Bite profile
Cheiracanthium bites are among the better documented spider bites in North America because the spider is frequently caught in the act, typically when trapped against skin by bedding or clothing. The typical presentation is immediate sharp pain, a small erythematous wheal, and resolution within a few days.
Older literature attributed necrotic lesions to this genus. Review of verified cases and controlled animal studies has not supported that attribution, and current clinical guidance treats these bites symptomatically.
Retreat sacs as an indicator
The flat silken sacs in ceiling corners are the most practical diagnostic sign of an indoor population. They are frequently mistaken for the beginnings of a cobweb. Physical removal of sacs combined with exclusion at siding and window frames is the appropriate management response.
Families most often confused with Cheiracanthiidae
| Family | How to separate it |
|---|---|
| Sicariidae | Recluses have six eyes and a violin-shaped carapace marking |
| Anyphaenidae | Ghost spiders have tracheal spiracles positioned well forward on the abdomen |
| Clubionidae | Sac spiders in the strict sense are generally darker and have a differently shaped retreat |
Profiled species in this family
| Species | Scientific name | Medical significance |
|---|---|---|
| Yellow Sac Spider | Cheiracanthium inclusum | moderate |
References
- [1]World Spider Catalog, version 26 - Natural History Museum Bern. Accessed 2026-06-14.
- [2]Spiders of North America: An Identification Manual, 2nd ed. - American Arachnological Society. Accessed 2026-06-14.
- [3]Common Spiders of North America - University of California Press. Accessed 2026-06-14.