The easiest way to tell a brown widow egg sac from a black widow egg sac is by texture. Brown widow egg sacs are covered in small, pointed projections that give them a spiky or tufted appearance, almost like a sandspur or a tiny sea urchin. Black widow egg sacs are smooth, with a papery surface and no bumps or spikes at all. If you’ve found a spider egg sac around your home and you’re trying to figure out which widow species made it, this single feature is the most reliable visual clue.
What Brown Widow Egg Sacs Look Like
Brown widow egg sacs are round and covered in silk projections that stick out from the surface. This spiky texture is unique among widow spiders and makes identification straightforward even without seeing the spider itself. The color is typically tan to light brown, sometimes with a slightly golden hue. Each sac holds roughly 120 to 150 eggs, and a single brown widow can produce around 20 egg sacs over her lifetime. That adds up to potentially 2,400 to 3,000 offspring from one spider.
Brown widows tend to place their egg sacs in sheltered spots around the exterior of homes: under patio furniture, inside the lips of flower pots, along fence rails, in the folds of stored outdoor equipment, and under eaves. They favor locations that are somewhat exposed rather than deeply hidden, which is why you’re more likely to stumble across their egg sacs during routine yard work or gardening.
What Black Widow Egg Sacs Look Like
Black widow egg sacs have a smooth, papery surface with no spikes or projections. The western black widow produces egg sacs that are yellow and either round or slightly pointed at the top. Southern and northern black widows produce egg sacs that are brown and oval, roughly half an inch long. The texture across all species is consistently smooth, which makes them easy to distinguish from the spiky brown widow sacs at a glance.
The egg count inside a black widow sac varies widely, from as few as 25 to more than 900. This enormous range depends on the species, the spider’s age, and available food. Incubation takes about 20 days before spiderlings emerge.
Black widows generally nest in darker, more secluded locations than brown widows. You’ll find their egg sacs in garages, woodpiles, crawl spaces, meter boxes, and undisturbed corners of sheds. They prefer low-traffic areas close to the ground where their messy, irregular webs won’t be disturbed.
Side-by-Side Comparison
- Surface texture: Brown widow egg sacs are spiky with silk projections. Black widow egg sacs are smooth and papery.
- Color: Brown widow sacs are tan to light brown. Black widow sacs range from yellow (western species) to brown (southern and northern species).
- Shape: Brown widow sacs are round. Black widow sacs are round to oval, sometimes pointed at the top.
- Eggs per sac: Brown widows average 120 to 150. Black widows range from 25 to over 900.
- Typical location: Brown widows favor semi-exposed outdoor spots like furniture and planters. Black widows prefer dark, undisturbed areas like garages and woodpiles.
Why Identification Matters
Both species are venomous, but their bites differ significantly in medical severity. Black widow venom is considerably more potent and can cause systemic symptoms including severe muscle cramping, abdominal pain, and in rare cases, complications requiring medical treatment. Brown widow bites tend to produce localized pain and irritation that stays near the bite site. Knowing which species you’re dealing with helps you gauge the level of caution needed.
Brown widows are also rapidly expanding their range across the southern United States and often displace native black widows in urban areas. If you’re finding spiky egg sacs where you used to see smooth ones, that shift is likely happening in your neighborhood. Brown widows reproduce prolifically, with up to 20 egg sacs per female, so populations can establish quickly once they arrive.
How to Remove Widow Egg Sacs
The simplest approach is vacuuming. Use a hose attachment to suck up the egg sac, then immediately dispose of the vacuum bag in an outdoor trash bin. If you’re using a bagless vacuum, empty and clean the canister outside. For egg sacs in outdoor areas, a broom or long-handled tool works to dislodge them. Collect and dispose of the sac rather than just knocking it to the ground, since the eggs can still hatch.
A solution of water and bleach or an oil-based spider pesticide can kill eggs on contact, which is useful for sacs tucked into crevices you can’t easily reach with a vacuum. If you’re finding multiple egg sacs, especially from black widows in hard-to-access spots like crawl spaces or wall voids, professional pest control is the safer option. A single brown widow can produce 20 sacs in her lifetime, so removing egg sacs without addressing the spider herself means new ones will keep appearing.
Check outdoor furniture, potted plants, and storage areas regularly during warm months. Reducing clutter around the exterior of your home eliminates the sheltered nooks both species prefer for nesting.