Diagnostic characters
- Anterior lateral spinnerets long, cylindrical, and clearly separated when viewed from behind
- Flattened dark grey to black body, often with a silky sheen
- Parson spider Herpyllus ecclesiasticus has a distinctive white dorsal stripe
- Runs in rapid, erratic bursts at floor level
- Found under stones, bark, and stored materials
Habitat and seasonality
Under rocks, logs, bark, mulch, and in leaf litter. Indoors along baseboards, in basements, and in garages.
Adults present spring through autumn; indoor encounters increase during autumn dispersal.
Medical significance
Low. Bites are uncommon and produce transient local pain.
Silk as a weapon
Several gnaphosid genera, notably Gnaphosa and Callilepis, discharge gluey silk from the enlarged anterior spinnerets directly onto prey while circling it. This allows them to attack other spiders and even ants with reduced risk of retaliation, an unusual offensive use of silk in a family that builds no capture web.
Household presence
Ground spiders are among the most frequently encountered indoor wandering spiders in the northern United States but are rarely identified correctly, being reported generically as fast black spiders. They are transient occupants that do not establish reproducing indoor populations, and exclusion at ground level is the appropriate response.
Families most often confused with Gnaphosidae
| Family | How to separate it |
|---|---|
| Corinnidae | Antmimics have conical spinnerets and often a constricted, ant-like body outline |
| Clubionidae | Sac spiders are pale and have conical, closely spaced spinnerets |
| Liocranidae | Spiny-legged sac spiders have conspicuous ventral leg spines |
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.