Yellow Sac Spider: Facts And Bites

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The Yellow sac spider is a venomous pest that is indigenous to the United States. They are typically light in color, but the shades can range from yellow to brown. 

They hide in their silken sac during the day and come out at night to hunt. Yellow sac spiders are not aggressive and will only bite humans if they feel threatened. 

However, these tiny arachnids can cause painful stings and inconvenient infestations. Therefore, it is essential to thoroughly explore all we need to know about yellow sack spiders: Facts and bites.

What is a yellow sac spider?

The yellow sac spider is a small, pale arachnid belonging to the biological genera Cheiracanthiu. They get their name from the yellow sac that they create to hold their eggs.

Spider sacking his prey after catch it dark background

The sac spider is commonly identified by the dark stripe running lengthwise down its abdomen. These spiders are often confused with other spiders, such as the brown recluse spider.

The front pair of legs of these spiders are generally longer than the other four, which enables them to push leaves or bushes out of the way while they are in search of prey.

These spiders are mainly nocturnal, meaning they are more active at night. They spin a silky thread during the night, which they use as a bridge to move from one spot to the other. They also build webs in high-traffic areas where insects tend to fly.

Yellow sac spiders are generally considered to be harmless to humans, and their bites are rarely serious. However, a yellow spider bite is more than a brown sac spider bite but less than a black widow spider or Brown recluse spider.

What Does The Yellow Sac Spider Look Like?

Female garden spider with eggs sac.

Typically cream-colored, a sac spider is also found in shades of light brown or gray. The average male is between four and eight millimeters, and the average female is between five and ten mm. 

Other distinguishable features include their characteristic yellow sac-like abdomen, yellow coloring on their legs, and the fact that their bottom legs do not point inward or outward as most spiders’ legs do.

When it comes to yellow sac spider locations, they can be found throughout the United States. These spiders are most active at night. These spiders are not aggressive and will only bite humans if they are disturbed.

However, these yellow spiders can be a nuisance when they infest a household. Furthermore, a sac spider bite wound is quite painful. 

Characteristics and History

Yellow sac spiders are light yellow to pale yellowish-green, occasionally with an orange-brown stripe on top of the abdomen. They possess eight eyes in two rows. Sac spider size typically ranges between ½ to 1 inch long.

It is a member of the family Sicariidae and is one of the most common spiders encountered in homes. They get their name from the silk sacs they produce, which they use to build webs and deposit eggs.

The yellow sac spider identification shows certain relations to other members of the spider family, such as black-footed yellow sac spider, yellowish-white spider, green sac spider, white sac spider, agrarian sac spider, black sac spider, and orange sac spider.

It can be said that the yellowish spider is a distant relative to these other spider species.

All yellow spiders build their webs close to the ground, often in dark, moist, undisturbed areas like under porches or in woodpiles. The eggs are deposited within a silken retreat, and the female will remain nearby to guard them.

Interestingly, C. mildei is more often encountered within man-made structures and oviposits almost exclusively indoors. Yellow sac spiders typically live for one year, and during that time, they will lay around 200 eggs.

The sac spider preys on other spiders, as well as insects. The young spiders often remain within the silken retreat for a short period and eventually venture out at night in search of food.

The young will frequently return at daybreak to hide within the protection of the retreat, thus ensuring their safety until they are old enough to fend for themselves.

Do yellow sac spider bite?

insect yellow sac

The simple answer to-do yellow sac spider bite is Yes. The yellow spider is recognized for its docile nature; however, it is known to bite humans only if threatened or disturbed.

The sac spiders are nocturnal and wander around at night; this makes the yellow spider more likely to come into contact with people, as they may be crawling around on the furniture or in bed when people are sitting or lying down.

And though sac spiders bites are not harmful to humans ( as it is not usually deadly), they can be very painful. 

If you are wondering what a yellow sac spider bite looks like, well, the yellow sac spider 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 as well.

Individuals sensitive to the sac spider may exhibit the following symptoms of yellow sac spider bite

  • day 1 yellow sac spider bite is extremely painful, eventually developing edema, pruritus, or erythema.
  • burning sensation and strong irritation, lasting for hours
  • blisters or rash development within the next 1 to 10 hours
  • ulceration or lesion resulting sac spider venom; however, it is not scarring in nature.

Where Are Yellow Sac Spiders Found?

Female poisonous spider Yellow Spider Sac

Yellow sac spiders can be located all over the world, in both tropical and temperate climates. However, these sac spiders are most common in the United States. They are often found in homes, garages, and other buildings.

Yellow sac spiders can be found outdoors under objects such as rocks, logs, and leaves during the summer months.

Indoors, they often like to hide in small, dark places, such as in corners of ceilings or walls painted a light, neutral color. Sac spiders prefer to live in dark, undisturbed areas where they can build their webs.

If someone disturbs a spider, they will usually fall to the floor and prefer to come out at night.

What Happens When A Yellow Sac Spider Bites A Human?

Yellow sack spider, Cheiracanthium sp, Amba, Kolhapur, Maharashtra, India.

Most people who a yellow sac spider bites will not experience any negative effects. However, when a yellow sac spider bites a human, the venom it possesses can cause some localized pain and swelling. 

While it is not considered a deadly spider, a yellow sac spider bite wound can lead to health complications requiring medical attention; this is particularly because some individuals may have a more severe reaction. 

Therefore, if you receive a yellow sac spider bite mark that develops welts, intense pain, or swelling after being bitten, you should seek medical attention right away.

That being said, as a precaution is always better than a cure, check out some ways to avoid Yellow Sac Spider Bites:

  • One of the best ways to avoid getting bitten by a yellow sac spider is to shake all of your clothes out before putting them on; this will help eliminate any spiders that might be hiding in them.
  • You can take other precautions, such as wearing gloves when gardening and checking bed sheets for spiders before getting into bed.
  • Installing spider traps in strategic locations around the house can prove helpful.
  • While their bites are not usually fatal, they can be quite painful. Therefore, if you do get bitten, first and foremost, always consult a professional. Even if you think you know what kind of spider bit you, there are many potential treatments for various spiders that only trained professionals can administer.
  • If the infestation becomes too much for you to handle, employ an exterminator to remove the spider and take care of the rest. Don’t attempt to solve the problem on your own.

Tips for Control

Clubiona sp

The best approach to dealing with yellow sac spiders is to remove the sacs and spiders hiding within. That being said, to prevent the yellow sack spider from invading your home, you can take some simple precautions:

  • You can also remove or limit heavy, ground-covering vegetation near the building as this will make it more difficult for them to establish webs and colonies.
  • Install tight-fitting screens on all attic and foundation vents.
  • Seal any holes around pipes in your basement or crawl space.
  • Make sure to remove any debris or clutter that may provide a hiding place for these spiders.
  • In addition, get your home professionally inspected for yellow sack spiders and any other potential pests that could cause harm to your family or pets.


On a closing note, let us explain that yellow sack spiders are frequently mistaken for cute due to their small size and distinctive color; nevertheless, one must never forget that yellow sack spiders are extremely dangerous and can bite anytime.

While their bites may not be lethal enough to kill a human, they can cause mild pain and discomfort for about a week or more than a week.

About the author

A biotechnologist by profession and a passionate pest researcher. I have been one of those people who used to run away from cockroaches and rats due to their pesky features, but then we all get that turn in life when we have to face something.