Black Widow vs. Brown Widow Spiders in San Diego: How to Tell Them Apart (and Keep Them Out)
If you grew up in San Diego, you learned to look for the shiny black spider with the red hourglass. But walk around most San Diego yards today and the widow you’re more likely to find is a mottled tan-and-brown one tucked under the patio furniture: the brown widow. Fall is when both are easiest to spot, and when they’re most likely to turn up around your home: black widows in garages, brown widows under patio furniture and play sets. Here’s how to tell them apart, how worried to be, and how to keep them out.
The black widow is shiny black with a red hourglass and hides in low, dark spots. The brown widow is tan to brown and mottled with an orange hourglass, and it shows up in more open spots around patios and play sets. The fastest tell is the egg sac: spiky for brown widows, smooth, yellowish and teardrop-shaped (tapered at the top) for black widows.
- Black widow: woodpiles, garages, meter boxes, and other dark, undisturbed spots.
- Brown widow: patio furniture, play sets, and chain-link fences.
- Both bite only defensively, and bites are uncommon. The black widow’s bite is the more serious of the two.
- Wear gloves when clearing clutter, and vacuum webs and egg sacs from eaves and outdoor furniture.
San Diego’s two widow spiders
California has two widow spiders, and San Diego County has plenty of both. The western black widow is the native species most of us grew up with. The brown widow is a relative newcomer, an introduced species that has spread rapidly across Southern California since it was first noticed here in the early 2000s (UC Riverside Center for Invasive Species Research).
University of California researchers have documented how quickly the brown widow has taken hold, and many Southern California residents now report that where they used to find a few black widows, they mainly find brown widows, often in larger numbers. In much of urban San Diego, the brown widow has become the widow you’re most likely to meet.
Native · more potent bite
Introduced · now very common
How to tell them apart in a few seconds
- Color. Black widow: shiny, solid black. Brown widow: tan, brown, and gray with a mottled or banded pattern, though some brown widows are quite dark.
- Hourglass. Black widow: red. Brown widow: usually orange rather than vivid red. (Both are on the underside, so don’t go looking up close.)
- Egg sac: the easiest tell. Black widow egg sacs are smooth, yellowish and teardrop-shaped (tapered at the top). Brown widow egg sacs are covered in little pointed spikes, like a tiny sea mine. If you see spiky sacs, you have brown widows.
- Location. Black widows hide in dark, enclosed spaces. Brown widows are bolder about open, exposed spots on and around outdoor furniture.
Why you see more widows in fall
Late summer and fall are when spider populations in Southern California peak. Spiders that hatched in spring are now full-sized, males are wandering in search of mates, and cooling nights push some of them toward sheltered spots: garages, patios, and the edges of homes. That’s why September and October bring the “suddenly there are spiders everywhere” calls. (It’s one of several seasonal shifts in our fall pest control guide.)
There’s also a food-chain reason. Spiders follow prey. When fall rain and cooler weather drive ants, flies, and other insects toward your home, the spiders aren’t far behind. Controlling the insects around your home is one of the most effective long-term ways to reduce spiders. (See why ants invade after the first rain.)
Where widows hide around San Diego homes
- Garages. Corners, shelving, stored boxes, and the gap under the garage door.
- Outdoor furniture. The undersides of chairs, tables, and cushions, especially pieces that rarely move.
- Kids’ play areas. Inside slides, under play-set platforms, and in stored outdoor toys.
- Utility boxes and meters. Always look before reaching into a meter box or irrigation valve cover.
- Shoes, gloves, and gear left outside. Shake them out before putting them on.
Bite risk: how worried should you be?
Both widows are shy. They bite defensively, usually when they’re pressed against skin, like a hand reaching into a glove or a foot sliding into a shoe. They don’t chase people, and bites are uncommon.
How to keep widows away from your home
- Declutter the garage. Store items in sealed plastic bins instead of cardboard boxes, and keep things off the floor.
- Move woodpiles away from the house. Keep firewood off the ground and well away from walls.
- Knock down webs and egg sacs. Use a long-handled broom or vacuum (then empty it outdoors). Removing the spiky brown widow sacs makes a big difference over time.
- Seal gaps. Replace worn garage door seals and door sweeps; seal cracks around windows and utility penetrations.
- Rethink outdoor lighting. Bright white lights draw the insects spiders eat. Warmer or yellow “bug” bulbs near doors help.
- Treat the prey, not just the spider. A professional program that reduces insects around the perimeter, plus targeted web and egg-sac removal, does more than any spray can.
AG Pest has helped San Diego families manage spiders and the insects that feed them for over 40 years. Our technicians know where widows hide in local homes, and we’ll explain what we find and what we treated in plain language. For the research-based background, the UC Statewide IPM Program’s Pest Notes on widow spiders is the best free reference. And if you’ve found termite pellets while cleaning out the garage, our guide to termite tenting vs. local treatment explains your options. Learn more about pest control in San Diego County.
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