Spiders, Pacific Northwest
Measuring 10 mm in length, yellow sac spiders are relatively small. As their name implies, these arachnids are predominantly pale yellow in color, although specimens also exist in hues of green, tan, straw, and light brown.
On close inspection, yellow sac spiders have dark mouth parts, and a band running laterally down their abdomen. The front legs of this arachnid are longer than their other 3 pairs. They are often confused with other spider species, and are easy to overlook.
Yellow sac spiders are found inside their flattened, silk tubes. In warm seasons, these spiders tend to reside in gardens, leaf piles, woodpiles, and timber. In fall, they migrate indoors and can be seen crawling up & down walls, as well as across ceilings, and vertical surfaces. Yellow sac spider populations increase significantly in fall, leading to indoor infestations.
These spiders hunt their prey at night, and move swiftly, wielding their front legs before them. They consume small insects and arthropods, as well as other spiders. Some yellow sac spiders have been known to feed on spiders much larger than themselves, and others will consume their own eggs.