Yellow sac spiders eat insects and other spiders. They hunt at night and don’t use webs to catch food. They are common in homes, where they sometimes bite, but they are not considered a serious health hazard.
What Yellow Sac Spiders Eat
These spiders (genus Cheiracanthium) are active hunters. They wander at night looking for prey instead of waiting in a web. Their food includes:
- Small insects such as flies, mosquitoes, aphids and moths.
- Other small spiders, including house spiders.
- Spider eggs and other small arthropods.
Some yellow sac spiders also sip plant nectar, which can help them through lean periods. Because they eat other pests, they can be useful outdoors, but most people don’t want them inside.
How to Identify One
Yellow sac spiders are small, pale yellow to light green or tan, and have a body about the size of a grain of rice to a small bean. Their front legs are slightly longer than the others. During the day they rest in a small, silky, tube-like sac, often where a wall meets the ceiling or in a corner of a window frame. That sac is where the name comes from.
Do They Bite?
Yellow sac spiders can bite, usually when pressed against skin, such as in bedding or clothing. The bite may sting and look red, itchy or slightly swollen, and typically heals within a few days. Extension entomologists say yellow sac spiders are not known to be a health hazard.
The old claim that their venom kills tissue is not well supported. Many “spider bites” are really other skin problems. If a bite looks infected, keeps getting worse or you have trouble breathing, see a doctor.
How to Keep Them Out of Your House
- Seal cracks and gaps around windows, doors and siding.
- Use door sweeps and tight window screens.
- Vacuum spiders, egg sacs and silk retreats, then empty the vacuum outdoors.
- Reduce clutter and keep stored items off walls and floors.
- Switch exterior lights to bulbs that attract fewer insects, because fewer insects mean fewer spiders.
- To remove one by hand, trap it under a glass and slide paper beneath it.
Related Reading
Learn what other spiders eat in our posts about tiny house spiders, black house spiders and house spiders kept as pets.
Bottom Line
Yellow sac spiders eat other insects and spiders at night. A bite is unpleasant but rarely serious. Sealing entry points and vacuuming silk retreats is the best way to keep them out.
