The Yellow Sac Spider (Cheiracanthium inclusum) is small and pale beige to yellow, often with a tinge of green. A distinctive darker lance-shaped mark runs down the midline of the forward portion of the upper surface of the abdomen. The dark brown chelicerae are large, elongate, and powerful and stand out against the paler body. Body length is around 4.9 to 9.7 mm for females and 4.0 to 7.7 mm for males (Kaston 1978).
Yellow Sac Spiders are often found running about on low trees and shrubs, where they make silken tubular retreats in rolled up leaves. During the day, they typically stay hidden in these retreats, coming out at night to hunt. During the winter, they build their tubular retreats under stones and tree bark.
Yellow Sac Spiders are found throughout most of the United States, with the exception of the northern tier of states (Kaston 1978). Although it has often been stated that their bites pose a danger to humans, the bite is apparently no worse than a bee or wasp sting (Fasan et al. 2008; Vetter and Isbister 2008), although in at least some cases symptoms may be quite unpleasant (e.g., Papini 2012).