Cheiracanthium Mildei – Northern Yellow Sac Spider

Cheiracanthium mildei, the northern yellow sac spider is one of the most common spiders in Northeastern America. However, it can be found throughout the entire USA.

The yellow sac spider can be identified by its greenish, yellowish color. During the daytime these spiders often hide in a small blanket of web under leaves and wood, but will often make their way into homes and hide in corners or under window sills.

Description of the northern yellow sac spider

The Yellow Sac Spider is one of the most common spiders found in Northeastern America. The abdomens are yellow to tan and often have a green tinge to the coloring. There is a darker stripe that runs lengthwise about halfway down the abdomen. The tips of their legs are often darker and the face of the cephalothorax is always darker.

Cheiracanthium Mildei - Northern Yellow Sac Spider
Photography by: K. J. Ester – Madison Heights, Michigan

Eyes

Yellow sac spiders have eight eyes. The eyes are all the same size and form four pairs of two eyes each.

Yellow sac spider closeup eye pattern face fangs Cheiracanthium mildei
A closeup of the eye pattern of a yellow sac spider. The eight eyes are grouped into four pairs of two eyes. Photo used with permission from Chase Noble.

Size

The body of the adult female will grow to about 3/8 of an inch (10 mm). If the legs are included, they can reach approximately 5/8 of an inch (16 mm) across.

Web

The Sac Spiders do not spin webs to catch prey. They are nocturnal hunters and during the day they will usually spin a web to create a thin cocoon-like sac to hide in. These are often found in the crease where a wall meets the ceiling or in windowsills.

Bites

Believe it or not, these little guys are one of the more dangerous spider species in the Northern United States. They are the most common spider to be bitten by and their bites are sometimes mistaken for that of the Brown Recluse. Although their venom is not nearly as dangerous as the Recluse’s, the bite can sometimes cause heavy swelling and even leave open sores.

There is a lot of bad info on the net that states that the Yellow Sac Spider uses the same cytotoxin as the Recluse does, but not as potent. I have recently learned from Rick Vetter, the top Brown Recluse expert in the world, that this is not true.

Cheiracanthium mildei Scientific Classification

  • Kingdom: Animalia
  • Phylum: Arthropoda
  • Subphylum: Chelicerata
  • Class: Arachnida
  • Order: Araneae
  • Infraorder: Araneomorphae
  • Family: Eutichuridae
  • Genus: Cheiracanthium
  • Species: Cheiracanthium mildei

Distribution of northern yellow sac spiders in the USA

Chiracanthium Mildei - Yellow Sac spider range USA

The northern yellow sac spider can be found throughout the United States. However, it is especially common in Northeastern America. Alabama, Alaska, Arizona, Arkansas, California, Colorado, Connecticut, Delaware, Florida, Georgia, Hawaii, Idaho, Illinois, Indiana, Iowa, Kansas, Kentucky, Louisiana, Maine, Maryland, Massachusetts, Michigan, Minnesota, Mississippi, Missouri, Montana, Nebraska, Nevada, New Hampshire, New Jersey, New Mexico, New York, North Carolina, North Dakota, Ohio, Oklahoma, Oregon, Pennsylvania, Rhode Island, South Carolina, South Dakota, Tennessee, Texas, Utah, Vermont, Virginia, Washington, West Virginia, Wisconsin, Wyoming.

Cheiracanthium Mildei – Northern Yellow Sac Spider

36 thoughts on “Cheiracanthium Mildei – Northern Yellow Sac Spider

  1. Found in my water cup this morning in east Pennsylvania. I’ve found quite a few of these spiders in my apartment. Haven’t really found webs for them. His body, excluding his legs, are pretty thin and tiny.

      1. Hello,
        I have been finding these spiders in my home everyday for months. How can I get rid of them? I’ve used home defense without any success.

        Thanks in advance.

    1. Hello ET, thanks for getting in touch! Yes, this does very much look like a Chiracanthium yellow sac spider.

  2. This doesn’t seem to match anything except maybe the yellow sac spider and that’s not really a good comparison 😕

  3. Is this a yellow male or female sac spider bite? It is a red dot in the middle and a white ring around it but doesn’t sting or swell but it itches more than it is painful and it had a yellow back but didn’t know if it had a little stripe

  4. Zoomed in 10x to get this shot. It’s a small spider. Hangs out in my bathroom. Have seen two of em before.

  5. I don’t know if this is a grass spider, yellow sac spider…? I seem to discover about 2 or 3 in every room. I would love if someone could identify it, though I realize it’s hard by this one picture.

  6. This specimen surprised us running across our patio after dark in Columbus. With legs, it was bigger than a half dollar. Any ideas?

  7. Sorry for low quality pictures. Is this a yellow sac spider/bite? I have seen these spiders on my car since camping in MN. My child also has a painful welt that looks raw in the middle on her head, wasn’t sure if it’s a spider bite. I’ll post the pic in another comment.

    1. Hi Hayly, this is most likely a yellow sac spider – it could also be a ghost spider (Hibana sp.).

  8. Sorry for low quality pictures. Is this a yellow sac spider bite? I have seen these spiders on my car since camping in MN. My child also has a painful welt that looks raw in the middle on her head, wasn’t sure if it’s a spider bite.

    1. Hello, this is almost certainly not a spider bite. Spiders only bite in very extreme situations. Almost all bites occur when someone reaches into the spider’s web/burrow or when they are pressed against the skin when they hide in clothing. While one bite is rare, bites to the head are extremely rare, two spider bites to the head are close to impossible. This is much rather a bite of some insect.

  9. Hi! I found this one while gardening, i think it may have gotten picked up with the leaves i was shoveling. The body itself was nearly an inch in length. Is this a yellow sac?

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