The brown widow spider was first spotted in Torrance, but they're now seen as far east as Moreno Valley.
The question for researcher Rick Vetter: How far will they go?
"Are they going to go further north? Are they going to get into Santa Barbara? Are they going to get into the Central Valley? These are things I'm interested in looking at," said Vetter, a research associate at the University of California-Riverside.
Unlike black widows that like to hide inside dark holes or say in your garage, Vetter says brown widows like the outdoors, specifically flat, small spaces like underneath patio furniture, the lips of potted plants and trash-can handles.
The other thing to be concerned about is playground equipment. Not corrugated flooring, but perhaps something like a flat area underneath a slide, places where kids might put their hands.
Vetter says compared with a black widow, there's not much to be concerned about.
"If you get bit by a black widow you have an 80 percent chance of developing a moderate to severe reaction to the bite, whereas most of the bites from a brown widow, the only symptoms are it hurts when it happens and there's a burning pain at the bite site," said Vetter.
So as mean as they might look, Vetter says, don't lose any sleep over them.