Yellow Sac Spider: All You Need to Know Simplified

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Yellow sac spiders, belonging to the Cheiracanthium genus, are fascinating creatures that have caught the interest of many. These spiders can be found in various parts of the world and are sometimes referred to as household spiders. The most common species of yellow sac spider include Cheiracanthium inclusum, Cheiracanthium mildei, and C. punctorium.

These small arachnids are usually yellow, white, or greenish in color, with a body length of about a quarter to a half-inch. They are known as active hunters, preferring to search for prey rather than spin webs to catch them. Yellow sac spiders may be encountered indoors or outdoors, with some species like C. mildei found more often inside homes.

Notably, yellow sac spiders have been reported to bite humans, causing a painful erythema similar to that of a bee or wasp sting. It is essential to be cautious around these spiders and to learn more about their behavior and habitats as you engage with the natural world around you.

Spider Identification

Physical Appearance

Yellow sac spiders have a small size with their body length ranging between 0.24 to 0.40 inches (6-10mm) for adult females and slightly smaller for adult males. Their color is predominantly pale yellow which gives the spider its name. The abdomen is cylindrical in shape and often appears much larger than the cephalothorax (front part of the body).

These spiders also have a pair of dark, forward-facing eyes, in addition to a set of six smaller eyes. Their legs are slender and relatively longer than their body, making them agile hunters.

Distinctive Markings

Yellow sac spiders have some distinguishing markings that can aid in their identification. One such feature is the orange-brown stripe that runs down the center of the cephalothorax, contrasting with the pale yellow background.

Some yellow sac spiders, particularly the black-footed yellow sac spider (Cheiracanthium inclusum), have a distinctive black-footed spider appearance due to their dark-colored leg tips. This marking helps differentiate them from other sac spiders.

  • Size: 0.24 to 0.40 inches (6-10mm) for adult females, slightly smaller for adult males
  • Color: Predominantly pale yellow
  • Abdomen: Cylindrical in shape, often larger than the cephalothorax
  • Eyes: One pair of dark, forward-facing eyes and six smaller ones
  • Legs: Slender and relatively longer than their body
  • Distinctive Markings: Orange-brown stripe on the cephalothorax, black-tipped legs for black-footed yellow sac spiders

By observing these characteristics, you should be able to identify a yellow sac spider with confidence. Remember, ensuring accurate identification is crucial for understanding their behavior and potential impacts on your environment.

Habitat and Distribution

Indoor Habitats

Yellow sac spiders can often be found indoors in various parts of your home. They prefer dark, secluded spaces like basements and attics. They may also choose to build their resting sacs on walls and ceilings, as well as hiding in woodpiles and other cluttered spaces.

Examples of indoor habitats include:

  • Basements
  • Attics
  • Inside closets
  • Behind furniture

Outdoor Habitats

Outdoors, yellow sac spiders can be found in a variety of habitats. They are highly adaptable and can be found across North America, Europe, and Australia. They are known to make their homes on plants, particularly in the leaves of trees or bushes. These spiders also favor gardens, where they can find plenty of prey insects. In addition to gardens, you might see them on the walls of buildings, especially near outdoor lighting.

Examples of outdoor habitats include:

  • Gardens
  • Trees and bushes
  • Walls of buildings
  • Woodpiles

Pros and Cons of Yellow Sac Spiders in Your Home


  • They help control insects, as they prey on small pests.
  • They are not aggressive towards humans.


  • Their bites, though rare, can be painful and cause skin irritations.
  • They may be a nuisance when found in large numbers.

Comparison Table of Indoor vs. Outdoor Habitats

Indoor Outdoor
Dark, secluded spaces Gardens, trees, and bushes
Basements, attics, closets Walls of buildings, woodpiles
Often found near human populations More spread out in various habitats

So, whether you find these spiders indoors or outdoors, it’s important to remember their important role in maintaining a balanced ecosystem. While they may be unwelcome in your home, their presence outdoors can be beneficial in keeping insect populations in check.

Behavior and Characteristics

Daily Routine

Yellow sac spiders are nocturnal creatures, meaning they are most active during the night. In the daytime, they usually hide in their silk sacs, which they commonly create in plants, under rocks, or inside the corners of your home. They venture out at night in search of prey, often wandering around instead of waiting in a web.

Preying Strategies

These spiders are unique in their hunting approach. Unlike some other species that rely on a web to capture prey, yellow sac spiders are considered “active hunters”. This means that they actively search for and hunt their prey. They possess the ability to jump, giving them an advantage when catching insects and other arthropods.

When hunting, yellow sac spiders usually display the following behavior:

  • Wandering around at night, covering large distances
  • Jumping in order to catch prey, using their strong front legs

It’s important to note that while yellow sac spiders are known to bite humans, this is usually a result of accidental contact. Bites often occur when the spider gets trapped between a person’s skin and clothing, sheets, or shoes.

By understanding their behavior and characteristics, you can better appreciate these fascinating creatures and take the necessary precautions to avoid any unwanted encounters.

Diet and Hunting

Yellow sac spiders are known for their distinctive diet and hunting tactics. They primarily feed on small insects, including other spiders. Let’s delve deeper into their prey preferences and hunting methods.

When it comes to their diet, yellow sac spiders have a variety of prey options. Some common examples include:

  • Aphids
  • Ants
  • Flies
  • Small moths

Yellow sac spiders are nocturnal hunters, which means they actively search for food at night. They employ a unique hunting strategy that sets them apart from other spiders. Instead of relying on a web to capture prey, they use their agile hunting skills. This involves:

  • Stalking and ambushing their prey
  • Using venom to immobilize their targets
  • Feeding directly on the incapacitated prey

By understanding the diet and hunting habits of the yellow sac spider, you can better appreciate this fascinating and skillful predator. Remember to keep a respectable distance when encountering them, as their bite can be quite painful. Stay aware and enjoy learning about these intriguing creatures.


Yellow sac spiders have a unique reproductive process involving egg sacs and spiderlings. Let’s dive into how these fascinating creatures bring new life.

When it comes to reproduction, yellow sac spiders start by creating silky egg sacs. These sacs contain several eggs, providing a safe environment for the developing spiderlings.

After laying their eggs, the female spider takes her parenting duties seriously. She closely guards the egg sac to ensure the protection of her developing offspring.

As the spiderlings hatch, they emerge from their egg sac ready to begin their lives. These baby spiders are quite independent from an early age and quickly take off to find their own homes.

To summarize:

  • Yellow sac spider females create egg sacs for their offspring
  • The sacs contain several eggs, providing a secure home for the developing spiderlings
  • Female spiders guard their egg sacs attentively
  • Spiderlings hatch independently and soon venture off on their own

Having a deeper understanding of yellow sac spiders’ reproductive process not only helps you appreciate these fascinating creatures but also allows you to be more informed about their life cycle and habits.

Spider Bite


When bitten by a yellow sac spider, you may experience a few different symptoms. These can include:

  • A painful, red bump appearing shortly after the bite
  • Swelling around the bite area
  • Possible nausea

Keep in mind, the yellow sac spider is not considered highly venomous, but its bite can still cause discomfort and irritation.


If you’re bitten by a yellow sac spider, it’s essential to take proper care of the bite area to avoid infection. Here are some steps to follow:

  1. Clean the bite area with soap and water
  2. Apply a cold pack to reduce swelling
  3. Elevate the bitten area if possible
  4. Consider over-the-counter pain relievers if necessary

In most cases, yellow sac spider bites can be treated at home. However, if symptoms worsen or infection occurs, it’s crucial to seek medical attention.


Preventing yellow sac spider bites can be achieved by taking certain precautions. Some tips to reduce your risk of getting bitten are:

  • Regularly clean and declutter your home to minimize hiding spots for spiders
  • Shake out clothing, shoes, and bedding before use
  • Seal any gaps in walls, windows, and doors that could allow spiders to enter

By following these prevention measures, you can minimize your chances of encountering a yellow sac spider and dealing with a painful bite.

Management and Control

Identifying Spider Infestation

Yellow sac spiders are small creatures that may infest your home. To identify if you have an infestation, look for these signs:

  • Presence of small, yellowish spiders with a dark stripe on their abdomen
  • Spiders found in cracks, corners, and gaps around the foundation of your home
  • Silken sacs in eaves, clutter, or debris

Remember to keep an eye on your gardening areas, as these spiders tend to be attracted to plants and shrubs.

Removal Techniques

If you do find an infestation, here are a few removal techniques:

  • Use a vacuum to suck up spiders and their webs from corners and cracks
  • Seal any gaps and holes around your home to prevent re-entry

In some cases, it may be necessary to consult a professional pest control expert to remove the infestation effectively.

Prevention Measures

To avoid future infestations, take these preventive measures:

  • Keep your living spaces clean and clutter-free
  • Regularly inspect your home for signs of spiders, paying attention to corners and eaves
  • Maintain your garden by removing debris and trimming shrubs to discourage spider habitats

By following these tips, you can effectively manage and control yellow sac spider infestations in your home.

Reader Emails

Over the years, our website, has received hundreds of letters and some interesting images asking us about these insects. Scroll down to have a look at some of them.

Letter 1 – Black Footed Spider


Location: SE lower Michigan
December 27, 2010 2:20 pm
Can you help me identify this spider? We have spotted them a few in our home.
Signature: H. Smith

Black Footed Spider

Dear H. Smith,
Your spider is a Black Footed Spider or Yellow Sac Spider,
Cheiracanthium mildei, a species that was introduced from Europe.  It was once believed to be a species whose bite could cause necropsy around the bite, but that speculation is no longer believed.  The revision can be read about on the American Journal of Tropical Medicine and Hygiene website.

Thank you so much for taking a look at it.
We really do appreciate this awesome service to those of us out here that have no clue as to how to identify these things.

Letter 2 – Black Footed Spider


Subject: Which spider?
Location: Anaheim,California
May 2, 2016 8:34 pm
Can you identify this spider for me. Sorry it’s not the clearest (I know, another one of those), but your best guess would be helpful. It was in my kitchen this morning and it’s the first time I’ve ever seen one near or in my house.
Found today, May2nd, 2016, in Anaheim, California. We live in an urban neighborhood, house built in the 60s. 64 degrees out, clear cool day.
Signature: Huh? “You’re the greatest”, “All my love”… Lol. Not sure what you mean, you pick.

Black Footed Spider
Black Footed Spider

Generally, the signature line in our standard form is used so that folks may use their real name or some funny phrase for those who want to maintain internet anonymity.  This is a Black Footed Spider or Yellow Sac Spider, Cheiracanthium mildei, based on this BugGuide image.  According to BugGuide, it is  “More often found inside man-made structures.”

Letter 3 – Sac Spider


Subject: Please ID spider
Location: Plattsburgh, NY
April 24, 2016 11:31 am
Trying to ID this critter.
Signature: Luke T. Bush

Sac Spider
Sac Spider

Dear Luke
Based on this and other BugGuide images, we believe this is a Sac Spider in the genus
Cheiracanthium.  According to BugGuide:  “Some species are thought to be slightly dangerous. However, this may not be true.”


  • Bugman

    Bugman aka Daniel Marlos has been identifying bugs since 1999. is his passion project and it has helped millions of readers identify the bug that has been bugging them for over two decades. You can reach out to him through our Contact Page.

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  • Piyushi Dhir

    Piyushi is a nature lover, blogger and traveler at heart. She lives in beautiful Canada with her family. Piyushi is an animal lover and loves to write about all creatures.

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4 Comments. Leave new

  • I live in ann arbor michigan they’re every where.I caught one in an empty pill bottle lastnight it freaked my girl out.

  • This does not really tell me about the spider. It only identifies it. I have found them in my home. Do they like dark or damp areas? Am I most likely to find their webs or nests in closets or basements? Are they quick to biter? Do I need to worry about them getting in the children’s beds at night? How do I get rid of them?

    • According to BugGuide: “They make a resting tube in a rolled leaf or under bark or stones. More often found inside man-made structures (as opposed to C. inclusum which is found more often outdoors).” BugGuide also states: “Yellow sac spider bites occur most frequently when the very defensive spider is trapped in clothing” and “Sac spiders are classified as hunting spiders. These spiders are very active at night and will emerge from their day resting sacs to run along walls and ceilings in pursuit of prey. If startled, they drop down on draglines and scurry away!” Since they are hunting spiders that are active at night, they might wind up in a bed. We do not provide extermination advice.

  • There’s been one of these on my front door for two days now.. in Tunisia! Small world, eh?


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