What Do Yellow Sac Spiders Eat?

Yellow Sac Spiders

( Cheiracanthium inclusum )


SIZE: About one-quarter of an inch in length.

COLOR: Pale yellowish-green.

BEHAVIOR: This spider belongs to a family of spiders known for resting in a small silken retreat or sac during the day. The yellow sac spider is a nighttime hunter that feeds on small insects and possibly even other spiders. As they wander about in search of prey, they sometimes crawl onto people sitting on a couch or lying in bed. The spider may then bite the person one or more times. The yellow sac spider likely accounts for more bites on people than any spider in the United States. Fortunately, the venom of this spider produces minimal effects. The bite usually forms a hard, reddened area that may measure from one inch to several inches in diameter, depending on the individual’s reaction to the venom. A white pustule typically forms at the bite site. Although the wound does not become ulcerating, it should be cleansed and disinfected. Any person receiving any perceived spider bite should consult a physician for treatment.


The yellow sac spider is common throughout the eastern United States, in particular from New England through the Midwest. It is normally an outdoor spider but will readily enter and breed inside homes and other buildings. The silken «sac» retreats are usually seen in corners along baseboards, along the ceiling, and beneath and behind furniture. Outdoors, the sacs will be found beneath the bark of trees and under items such as stones and logs. Sacs may also be found along soffits, beneath window sills and around door frames.

Tips for Control

The best approach with this spider is to find, destroy and remove the sacs and the spiders hiding within. Steps to be taken to prevent new spiders from entering include:

Removing or limiting heavy, ground-covering vegetation near the home.

Sealing cracks and holes in the building’s exterior.

Installing tight-fitting screens on all attic and foundation vents.

Sealing holes around pipes indoors to prevent spiders from entering the living spaces of the home from basements and crawl spaces by following plumbing lines.

Where numerous spiders and bites have occurred, a professional should be consulted to conduct a thorough inspection and recommend possible treatments.



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Facts on the Yellow Sac Spider

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Yellow sac spiders prefer the great outdoors but will venture indoors to hunt tasty bugs. Although the spiders don’t actively seek out people, they will bite humans if threatened. Most people experience only mild reactions to yellow sac spider bites, but some develop more serious symptoms that require medical care.

They Are What They Eat

Yellow sac spiders get their name from the sacs they build to conceal themselves while they wait for prime hunting hours in the evening. The spiders are light yellow to yellow-green in color. Some have darker stripes on their abdomens that look orange or brown. The University of Michigan’s Animal Diversity Web site says the spiders’ body colors vary by the type of insects they eat and notes that spiders who eat flies tend to have grayer bodies, while spiders that eat red-eyed fruit flies look slightly red. Yellow sac spiders range in length from slightly less than a quarter-inch to three-eighths of an inch. Male spiders’ bodies are a little smaller than the females’, but they have longer legs.

See also:  What Does A Spider Sack Look Like?

Cozy Homes

Other spiders spend hours constructing intricate webs, but yellow sac spiders can create sacs in just 15 minutes. The spiders’ sacs are about an inch in length and look like small white cocoons. Yellow sac spiders build their sacs in the places bugs hang out; they prefer making their homes in weeds, in tall grass or under leaves. If you’ve ever noticed a small white cocoon in the corner of a room or at the spot where the ceiling and wall join together, you’ve probably hosted a yellow sac spider in your home.

Finding Food

Yellow sac spiders aren’t particular and will eat almost any insect or insect egg they find. Their front legs are longer than their other legs, which helps them hunt. The spiders use those legs to push aside leaves and vegetation to search for bugs. A collection of dark hairs at the bottoms of the spiders’ legs help them cling to trees and walls when they climb. When the weather turns colder, the insect population declines outdoors and the spiders begin entering homes and other buildings to find food.

Accidental Victims

When darkness falls, the yellow sac spider produces a silky thread and either drops to the floor or uses the thread as a sort of a bridge to another spot in the room. If the spider happens to drop onto your bed, he might bite you in his haste to escape from your clothing or sheets. You might notice a sharp, burning pain when a yellow sac spider bites you. In most cases, the bite will heal on its own without causing any major problems. Some people experience more severe reactions to the spider’s bite and can develop an ulceration at the bite site, fever, nausea, fatigue or abdominal cramps. A prescription antibiotic can help treat symptoms of a severe reaction.

References (3)

  • Animal Diversity Web: Cheiracanthium Inclusum
  • Utah State University Extension: Yellow Sac Spiders
  • Ohio State University Extension Fact Sheet: Sac Spiders


Working at a humane society allowed Jill Leviticus to combine her business management experience with her love of animals. Leviticus has a journalism degree from Lock Haven University, has written for Nonprofit Management Report, Volunteer Management Report and Healthy Pet, and has worked in the healthcare field.


Yellow Sac Spider

The Yellow Sac Spider

The yellow sac spider is a hunter, chasing prey instead of catching it in webs. They eat insects, other spiders (including larger spider species), their mates, and sometimes their own eggs.

Comparatively aggressive, and prevalent, most spider bites come from a yellow sac spider. Females usually lay six sacs of eggs, averaging 37 eggs per batch. They cover these eggs with loose silk.

What do Yellow Sac Spiders Look Like?

The yellow sac spider is often yellow and can range in color to tan, light brown, and pale green depending on location and diet.

They have a brown stripe down the back of their abdomen over the area where their heart is. They have long, sharp fangs that easily pierce human skin.

Yellow sac spiders are small, ranging from under a quarter-inch to a little less than half an inch.

They have unusually long legs, with the front pair longer than the others. Their legs are covered with stiff black hairs that make them excellent climbers. These hairs are thickest at the bottom, causing them to be known as black feet spiders as well.

Yellow Sac Habitat

Species of the yellow sac spider are common around the world. Two species live throughout the United States, one native and one introduced from Europe. The European yellow sac spider is darker, verging on orange.

During the spring and summer, they prefer to stay outside. Come fall, immature spiders migrate inside. They do not build webs, but spin small sleeping sacks in high, out of the way places. Outside they inhabit foliage on the edge of empty spaces and gardens. Inside they prefer the joint between wall and ceiling, corners, and behind pictures.


Yellow sac spiders stay near their eggs and defend them. They are nocturnal, leaving their sac to hunt at night. They are great climbers and hang out in high places or dark hollows where they feel safe.

Like all spiders, they bite when pressed against the skin. As they love gardens, they are often disrupted and bite threats to their homes. Unlike most spiders, they will bite when startled and have been observed to do so for no reason.

They are rumored to be attracted to car engines and the smell of gasoline. While they are often found inside cars, this is considered most likely due to their numbers and size.

Yellow Sac Spider Bite and Treatment

The yellow sac spider bite is similar to that of the brown recluse or black widow, but less severe. As they easily pierce the skin, their bite is initially as painful as a wasp bite.

From one to ten hours later the burning sensation may turn into blisters or a rash. Sometimes the bite kills tissue – though it is smaller than the brown recluse – heals in days instead of weeks, and rarely scars.

See also:  What Does The Start Of A Spider Bite Look Like?

Recipients of the bite may develop fever, cramps, nausea, and malaise. These symptoms and bites are, as with all bites, higher risk in children, the elderly, and the infirmed.

Seek medical attention if bitten by a yellow sac spider, just in case.

Croach® Spider Control

Spider control services customized for you will include:

  • Inspection with individual plan and proposal
  • Initial treatment to remove webs and sacs, and eliminate existing spiders, including interior
  • First regular treatment thirty days later, breaks egg cycle and eliminates remaining spiders
  • Regular treatments to apply product and remove webs, frequency dependent on severity (Fall and spring treatments lessen the risk of yellow sac spider infestation)
  • Complimentary retreats when necessary
  • Interior treatments upon request

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Yellow sac spider

While many spiders exist, the yellow sac spider is one of the more common ones encountered. This creature may be located in your home or business and given that it’s a venomous pest, it warrants your attention. Learn more here about the yellow sac spider’s appearance, lifestyle and most importantly – its bite.

Find out some basics about the yellow sac spider below. And if you’re stressing about yellow sac spiders where you live or work, call Western Exterminator at 800-937-8398 or contact us online to get in touch with a pest expert.

Yellow sac spider problems?

Have you noticed what looks like a yellow sac spider? Contact Western right away!

What is a sac spider?

A sac spider typically creates a flat silk sac as the place where it passes most of the daytime. This sac may be located in a shielded spot, like where a wall and ceiling meet, or in a leaf. In fact, they do not create webs. Sac spiders are commonly pale. They have eight eyes that are in two rows. Female sac spiders lay 30 to 48 eggs and put silk over them.

Yellow sac spider species

North America has two species – cheiracanthium inclusum and cheiracanthium mildei – that are known as yellow sac spiders (both occur in California). It is believed that C. mildei was introduced from Europe. You will more commonly find C. inclusum outside and C. mildei inside. C. inclusum is not found in the most northern states of the U.S.

C. mildei adult females have bodies that are ¼ to ⅜ inches in length (males are 3/16 to 5/16 inches). This spider can be light green to yellow-white in color and the legs are darker. Its jaws are brown. C. inclusum adult females are 3/16 to ⅜ inches in length and males are ⅛ to 5/16 inches in length. These spiders can be light yellow in color but otherwise resemble C. mildei. The abdomen of C. inclusum and C. mildei has a stripe that’s a bit darker.

For reference, the yellow sac spiders described here are smaller than a quarter in size. However, it is noteworthy that yellow sac spiders are not always yellow in color.

C. mildei and C. inclusum hunt and eat at night. C. mildei can be located at ceiling-wall corners, and you might notice them moving on ceilings and walls in the nighttime. C. inclusum can be found in a garden and can conceal themselves under bark when it’s daytime. C. mildei and C. inclusum can move into buildings or cars during the late summer and early in the fall to spend the winter.

Are yellow sac spiders poisonous?

Yellow sac spiders are venomous. You could get bitten if this creature is caught in your clothes. A C. inclusum spider may bite you if you are outside working in your garden. It’s possible for a yellow sac spider bite to be misidentified as the bite of a brown recluse spider. If you are bitten by a spider, try to catch it in order to have it identified.

Yellow sac spider bite symptoms

The yellow sac spider’s bite can hurt. A paper published in 2006, “Verified bites by yellow sac spiders (genus cheiracanthium) in the United States and Australia: where is the necrosis?”, covered 20 cheiracanthium genus spider bites from the U.S. and Australia and found that in all instances, people experienced pain or discomfort. It lasted for an average length of 1 hour and 45 minutes. One person dealt with a headache and someone else experienced nausea and vomiting.

If you are bitten by a yellow sac spider, you may experience redness, swelling, and burning. Some suggest applying hydrogen peroxide to where you have been bitten and using an ice pack to decrease swelling. But we always recommend checking with a professional for treatment advice. And certainly, if you encounter nausea, vomiting, headache or other types of severe issues, seek medical attention immediately.

How to get rid of yellow sac spiders

If you’re seeking to control yellow sac spiders, get rid of silk sacs – especially ones located where the ceiling meets the wall and at the corners of the ceiling. You can use a vacuum to eliminate the sacs, but bring the bag outdoors when you are finished.

See also:  What Makes A Spider Web Sticky?

Even though you can try to battle a spider problem yourself, we know that pest issues can get out of hand. If that’s the case, you should turn to a professional. Fretting about yellow sac spiders or other spiders on your property? Reach out to Western Exterminator today to find out how our experts can help!

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Yellow sac spiders in Seattle

The yellow sac spider is a common pest in the Seattle area. Our specialists know how to handle them and any other spider you might encounter.

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Yellow Sac Spiders

Facts, Identification, & Control

Scientific Name

Cheiracanthium inclusum and Cheiracanthium mildei

Appearance / Identification

How Did I Get Yellow Sac Spiders?

Like most other types of spiders, these pests don’t necessarily want to live near people. Yellow sac spiders may wander inside through an open door or follow infestations of prey insects that may wander inside a home.

Fall is the most common time to notice them indoors, as they may also come into houses seeking shelter from the cold. In the summer, yellow sac spiders usually live in gardens and under debris located on the ground.

How Serious Are Yellow Sac Spiders?

Yellow sac spiders are nighttime hunters that search for prey rather than catching their prey within a web. Therefore, these spiders may come into contact with people if they should be trapped between a person’s skin and bed sheets, clothing, or shoes. They may also bite if a person provokes the spider while gardening or working in a location of preferred habitat.

Bites from a yellow sac spider can be painful and mildly necrotic, meaning that the venom will damage and kill skin tissue. People often misdiagnose these wounds as brown recluse bites, even though they are much less severe. Reactions to a bite may include a slow-healing sore, itchiness, and swelling. These bites are not considered to be extreme, medically important venomous biters and are usually not a cause for concern.

Signs of Infestation

The appearance of either immature or mature spiders and their protective sacs are signs of a yellow sac spider problem.

How Do I Get Rid of Yellow Sac Spiders?

Yellow sac spider prevention is best accomplished by sealing holes, cracks, and gaps in the home’s doors, windows, and foundation that enable the spiders to enter the home. Removing inside clutter that serves as harborage for spiders is also helpful.

What Orkin Does

Your local Orkin technician is trained to help manage yellow sac spiders and similar pests. Since every building or home is different, your Orkin technician will design a unique program for your situation.

Orkin can provide the right solution to keep yellow sac spiders in their place…out of your home, or business.

Behavior, Diet, & Habit

Yellow sac spiders usually feed on other spiders, plus agricultural and garden pest insects and their eggs. If food sources are limited, these spiders become cannibalistic and may consume their own eggs.

Where Do They Live?

Yellow sac spiders are usually most active at night, and during the day will retreat to their web masses (sacs) for protection against predators. Outdoors, these spiders normally are found hiding in rolled up leaves or in other debris in small, hidden locations. In addition to protection, these daytime hiding places also function as molting sites (shedding of their outer «skin» in order to grow larger), mating, egg laying, and hibernating sites. Their preferred habitats around the home are in:

  • Bushes
  • Gardens
  • Leaf piles
  • Trees
  • Woodpiles

Geographic Range

Yellow sac spiders are found throughout most all of the United States, but are fewer in number within the northern, colder climates.


Male yellow sac spiders will hunt for females and breed with them in the early summer. Females typically mate only once but produce as many as five egg sacs, each of which contains approximately 40 eggs. Their egg sac serves to protect not only the mature spiders, but also to protect the eggs and immature stages of the yellow sac spider.


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