About Yellow Sac Spiders

The Yellow sac spider (Cheiracanthium inclusum) is a pale yellow or light green spider that measures about ¼ inch long. Instead of building large webs, these spiders create small silken sacs in corners, along ceilings, or behind objects where they hide during the day and emerge at night to hunt.

Risks & Concerns

Yellow sac spiders are more likely to bite humans than many other spiders, often when accidentally disturbed. While their venom is not considered dangerous, bites can cause localized redness, swelling, and discomfort that is sometimes mistaken for a brown recluse bite. In Boston homes and offices, their presence can be unsettling even if infestations are small.

Prevention & Control

Keeping areas free of clutter, sealing cracks, and maintaining regular cleaning schedules helps limit their hiding places. Because they follow insect prey indoors, controlling other pests also helps reduce their activity. Sticky traps and regular monitoring can help detect their presence, but ongoing spider problems are best managed with professional inspection and treatment.