Yellow Sac Spider

The yellow sac spider is believed to be responsible for more spider bites than any other species. While the brown recluse spider gets blamed for hundreds of bites per year, there is little data available to support the frequency of such occurrences and it is believed that the sac spider is responsible for most of these reports. The poison carried by sac spiders is known as a cytotoxin, which means anything that is toxic to cells. These spiders will occasionally enter residential structures and are treated the same way as wolf spiders.

Yellow Sac Spiders

Yellow sac spiders usually have pale colored bodies, normally without markings. The chelicerae (spider mouth parts) are visibly darker than the rest of the body and they may occasionally have a stripe running the length of the abdomen. Outdoors, they can be observed creating tiny silk shelters in leaf debris, rocks, and other plant life. This is where the female will lay and guard her eggs. Sac spiders can be found on nearly every major continent.

Behavior & Facts

Sac spiders prefer outdoor areas and are nocturnal. They are wandering spiders, which means they rely on hunting prey instead of catching it in a web. Sightings reportedly increase during the transition into cooler temperatures, where they may enter homes in search of warmer climates and other insects. They are unable to thrive in a home environment. Chemo receptive hairs on their forearms are used in the detection of prey.

Yellow Sac Spider Bite

Several reports indicate the yellow sac spider bite can leave a nasty skin lesion, while others report swelling that lasts up to three weeks. This is especially common in the veterinary field, where the yellow sac bite is often responsible for unusual bites or lesions appearing on pets. Treat skin with hydrogen peroxide or vinegar and seek medical attention in the event of an allergic response. Cool with an ice pack and confirm the identity of the spider before speaking with a doctor, if at all possible.