Sac Spiders
Sac spiders are small to medium-sized pale yellow or green spiders that are among the most frequently encountered biting spiders in the United States. They do not build prey-catching webs but construct small, tube-shaped silk retreats (sacs) in upper corners of rooms, behind pictures, and where walls meet ceilings. They are active nighttime hunters that roam walls and ceilings searching for prey. Many verified spider bites in homes, previously attributed to brown recluses, have been re-examined and attributed to yellow sac spiders.
Species in This Group (2)
Yellow Sac Spider
Cheiracanthium inclusum
The Yellow Sac Spider is one of the more commonly encountered biting spiders in U.
Parson Spider
Herpyllus ecclesiasticus
The Parson Spider is named for the distinctive white marking on its abdomen that resembles the cravat worn by clergy in the 18th century.
Key Behaviors
Sac spiders build fresh silk retreats each day, typically in the angle where walls meet ceilings. They emerge at night to hunt, walking across walls, ceilings, and other surfaces. They are attracted to prey congregating around indoor lighting. During cold weather, they move indoors in large numbers. In vehicles, they occasionally build sacs in side mirror housings and fuel system vent lines.
Risks & Concerns
Sac spider bites produce localized pain, redness, and swelling similar to a mild bee sting. Some individuals experience mild necrosis at the bite site, though this is debated. They are the most common source of indoor spider bites in many regions. Their nocturnal wandering and habit of crawling across beds and furniture increases bite probability.
Identification Tip
Often confused with brown recluse spiders as a cause of necrotic bites. Sac spiders are distinguished by their pale coloring, lack of a violin marking, and habit of building silk sacs in upper room corners. They are found throughout the U.S. while brown recluses are limited to the south-central region.
Quick Comparison
| Species | Size | Color | Key Trait |
|---|---|---|---|
| Yellow Sac Spider | 5-10 mm | Pale yellow to light green with darker chelicerae | Pale yellow color; builds small silken sacs in corners where walls meet ceilings; nocturnal hunter. |
| Parson Spider | 8-13 mm (body length) | Dark brown to black with a distinctive white or gray dorsal stripe on the abdomen resembling a clerical cravat | White or gray abdominal marking shaped like an old-fashioned clerical collar (cravat); fast runner that does not build webs; active nocturnal ground hunter. |
Need Help With Sac spiders?
If you're seeing signs of sac spiders in or around your home, professional treatment is the fastest way to stop the problem. Lotus Pest Control offers free inspections to identify the issue and recommend the right solution.