Most spider egg sacs around Los Angeles homes come from four groups. Black widows make a yellow to light tan sac, round or teardrop-shaped, with a tough papery wall. Brown widows make a white to tan sac covered in silk spikes. Cellar spiders carry silk-wrapped eggs in their jaws. Orb weavers leave a brown papery sac in the web. One widow sac holds 130 to 300 eggs, so bag it with a vacuum or a gloved hand, never a spray.
What do spider egg sacs look like in Los Angeles?
Texture, shape and placement tell the four groups apart.
- Western black widow. Creamy yellow to light tan, round or teardrop-shaped, about half an inch across, with a tough, papery wall that UC IPM says is difficult to rip apart. It sits in a web of tangled silk near a hole, crevice or pile of clutter.
- Brown widow. White to tan, about half an inch across, covered in pointed silk projections like a sandspur seed. UC IPM says the sac alone confirms brown widows, even if you never see the spider. Check the undersides of plastic patio chairs first.
- Cellar spiders. The female wraps 25 to 60 eggs in silk and holds the bundle in her jaws while hanging upside down in her web. In California the marbled cellar spider has displaced the once common longbodied cellar spider. Both are harmless to people.
- Orb weavers. The yellow garden spider deposits a spherical, brown, papery sac in its web in late summer. The spiderlings emerge from it in early spring.
How many baby spiders hatch from one egg sac?
Between a few dozen and several hundred, depending on the species.
- A western black widow lays about 300 eggs per sac and can produce more than 10 sacs without mating again, according to UC IPM.
- UC IPM counts about 130 eggs per brown widow sac and 20 or more sacs per lifetime, which adds up to thousands of eggs. Clemson Extension reports about 250 eggs per sac. Females are often found with several sacs developing at once.
- Clemson reports brown widow eggs hatching in 14 to 21 days, with the spiderlings staying inside the sac for four days to a month.
- A cellar spider carries 25 to 60 eggs per cluster.
- A yellow garden spider sac releases 500 to 1,000 spiderlings in early spring, according to Penn State Extension. Many die early to cannibalism and mud dauber wasps.
What is ballooning, and why do baby spiders keep showing up?
Ballooning is how spiderlings leave the nursery. Each one climbs a fence post or plant, raises its abdomen and releases silk until the wind carries it off. UC IPM reports ballooning spiderlings captured at 10,000 feet above the ground and 200 miles offshore, and says they drop onto your property continually. It concludes that eliminating them needs to be done repeatedly throughout the year, which is why a one-time spray rarely ends the problem.
Our post on why spiders are in your home and what they're really after covers the lights, water and clutter that decide where they settle.
How do you remove a spider egg sac safely?
Bag it with a vacuum or a gloved hand, and do not spray it.
- Put on gloves and long sleeves. UC IPM says widow bites are rare but still recommends gloves when clearing clutter.
- Find the female first. Widows sit in the middle of the web, underside up. A black widow shows a red hourglass underneath. A brown widow has a mottled tan, brown and gray body, dark-banded legs and a yellow to orange hourglass.
- Vacuum the sac, the web and the spider with a hose attachment. UC IPM notes that spiders' soft bodies usually do not survive the tumble through the hose. Without a vacuum, scrape the sac into a zip bag with a putty knife.
- Seal the bag and put it in an outdoor trash bin. Clemson Extension suggests a chest freezer for several hours first.
- Skip the spray. Water-based insecticides had no significant effect on brown widow eggs in a 2016 study UC IPM cites.
- Recheck the spot in two weeks. A female that escaped will rebuild and lay again.
When does an egg sac mean a widow infestation?
One sac means a mature female has lived there long enough to mate and lay. Several sacs mean a resident population.
- One sac in one web: a single female. Remove all three, then check the rest of the yard.
- Three or more sacs in one web: a female that has been producing for weeks, with hundreds of spiderlings on the way.
- Sacs in several places: under more than one chair, along a railing, in a stack of flowerpots. That is a breeding population, and the neighboring yards are probably seeded too.
In urban areas the widow you find is now more likely brown: UC IPM reports brown widows appear to be displacing black widows there. A 2012 study it cites found them outnumbering black widows in urban areas. UC IPM calls them extremely common under inexpensive plastic patio furniture and in outdoor clutter such as woodpiles.
Black widows nest in holes, crevices and clutter; in garages they usually web by doors and near vents. UC IPM describes the brown widow bite as much milder than the western black widow's, so treat a black widow site with extra care.
When the count points to a population, PesPro's spider control service removes the spiders, clears webs and creates a perimeter barrier. We also address the insects that attract spiders. Our bi-monthly or quarterly general pest control program also covers spiders, since ballooning brings new spiderlings every season. Spiders fall under the "all other pests" tier of our 30-day guarantee: if you need another visit within 30 days, you pay 30% of the original price.
Same-day service is available for an extra fee and depends on the day's route. The written quote is free. Request a quote for any address in Los Angeles County or San Bernardino County.
How do you keep spiders from laying eggs around your home?
Take away the prey, the shelter and the undisturbed corners. UC IPM notes that outdoor lighting attracts insects, which in turn attract spiders, so keep fixtures off the structure and away from windows and doors. Keep clutter off the floor indoors and away from the foundation outdoors. Flip patio furniture regularly in warm months and remove webs from the exterior with a broom or a high-pressure hose. Seal cracks in the foundation and gaps around windows and doors.
Frequently asked questions
Are spider egg sacs dangerous to touch?
The sac itself carries no venom. The risk is the female guarding it, usually within a few inches. Wear gloves, look before you reach, and never squeeze a sac in bare hands. Clemson notes that hatched spiderlings can stay inside the sac for up to a month, so a sac that looks quiet may be full of live spiders. Brown widow spikes are soft silk and cannot hurt you.
What should I do after a black widow bite?
Wash the bite with soap and water, apply a cloth dampened with cold water or filled with ice, and elevate the area if you can. Do not try to remove the venom. CDC/NIOSH describes the venom as a neurotoxin that produces pain at the bite area and then spreads to the chest, abdomen or the entire body. NIOSH says death is extremely rare, but seek medical attention right away.
Does spraying kill spider eggs?
Usually not. In the 2016 study UC IPM cites, water-based insecticides sprayed on brown widow egg sacs had no significant effect on the eggs inside. Only petroleum-based products penetrated the silk. UC IPM also states that insecticides will not provide long-term control and should not generally be used against spiders outdoors. Pull the sac off and bag it; treatments belong on the perimeter and on the insects spiders eat.
Why are there tiny spiders all over my house?
Either a sac hatched indoors or spiderlings ballooned in through open doors, screens and vents. Vacuum them, then find the source behind furniture, in closet corners, in the garage and under window sills. Cellar spider young are harmless. Tan spiderlings with mostly white abdomens marked by a few black spots, near a web of tangled silk, are young widows. Treat that spot as a widow site.