Steatoda identification

[programmatic]

I've been finding a lot of these at my home in Northern California. Despite my research, I'm having a hard time arriving at a confident species identification. Would appreciate any experienced input.

I found both of these together, along with silky white egg sacs. They're skittish and seemingly aggressive. Fast on the ground. Strong silk that I could hear and feel breaking as I moved an old board in my backyard- was surprised it wasn't a true widow.

The larger 6 1/2 legged one doesn't have any markings on its dorsal side. I've attached a close up of its ventral side that I managed to snag.

 

[programmatic]

Update- further reading around here and other sites is leading me to believe it is indeed Steatoda Grossa, as initially suspected. I was trying to confirm between grossa and borealis. Given location of the find, and the differences in pattern on ventral side of abdomen (finally found a good reference photo of borealis ventral side), I'm now 99% confident in grossa but of course still welcome any experienced input.

I should also clarify what I meant about it seeming aggressive. It was not aggressive toward me, but rather toward an L. hesperus that I tried feeding one of them to. Well, only after I separated them did I learn that these spiders are good fighters who've learned to standup to black widows' capture/webbing attempts.

 

[The Snark]

Update- further reading around here and other sites is leading me to believe it is indeed Steatoda Grossa, as initially suspected. I was trying to confirm between grossa and borealis.

I don't think Borealis is in Calif.

 

[SilentWidowMaker]

Looks like S. grossa

 

[Ungoliant]

I've been finding a lot of these at my home in Northern California. Despite my research, I'm having a hard time arriving at a confident species identification. Would appreciate any experienced input.

The ones you find in California are usually Steatoda grossa, S. nobilis, or S. triangulosa. I believe this is S. grossa.