Yellow Sac Spider

The yellow sac spider, Cheiracanthium inclusum (Hentz), is a common arboreal spider in the family Cheiracanthiidae. Adults are pale yellow to light green, with dark brown chelicerae and often a darker stripe dorsally on the abdomen, measuring 4-9 mm in body length. They possess eight eyes arranged in two rows. These spiders do not construct true webs for prey capture but instead build silken retreats, or sacs, in curled leaves, under bark, or indoors in corners and wall/ceiling junctures. Mating occurs in late spring to early summer, with females laying 30-70 eggs in their silken sac, guarding them until they hatch. They typically live for about a year.

Cheiracanthium inclusum is a nocturnal hunter, actively foraging for insects and other small arthropods on foliage and around structures. During the day, they retreat to their silken sacs. Unlike many spiders, they are frequently found indoors, especially during cooler months, seeking shelter. Bites from yellow sac spiders are a common concern, often occurring when the spider is accidentally pressed against the skin. Although the venom is not considered medically significant, bites can be painful, causing localized redness, swelling, and sometimes a necrotic lesion.