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Juvenile western black widow - california - Latrodectus hesperus

Juvenile western black widow - california - Latrodectus hesperus
Santa clarita, Los angeles County, California, USA
October 16, 2014
Size: Small
This wonderful specimen was hiding in my mailbox late at night. Bit me when I put my hand in mailbox to retrieve mail. Felt a prick. Within 20 feet. Hand swelled up, arm numbed up, stomach cramps, diarrhea and terrible headache. Called 911. Vitals were fine. Basically you get watched at hospital with tylenol and mottin for any allergic reactions ( swollen tongue etc ) so decided to stay home. A week later my hand swelled up again. Doctor says poison still in my system. Such a small spider with big consequences. Didn't originally think it was a black widow since it is not black. Wanted to share. How do you know though if it is a male or female ?

I am fairly sure

Species ID based on ...
the abdominal median spots being fused into one stripe and the adjacent designs (they look like eyes) on either side having less white wrapped around the black spots.

The median spots being fused, and even containing the red marking, is a trait common to the two species. You can see that feature on L. geometricus in this picture.
The feature I find is the best for distinguishing the two species is the marking at the anterior of the abdomen. In L. hesperus the marking is U-shaped and it connects at the front like in the first image you linked there. In L. geometricus the marking is V-shaped and doesn't usually connect at the vertex as in this picture.
I'm no arachnologist or anything, though. That's just what I've observed.

The first image ...
you have linked to for comparison does not show a completely fused set of spots, some of them are separate. The anterior spots are the ones I'm looking at, I haven't seen any confirmed L. geometricus where all of the spots are fused into a line but drawings of L. hesperus in Kaston, 1970(1) are depicted this way. I don't think enough of the anterior abdomen is visible to discern whether or not the white markings there connect. Illustrations of the two species in "Field Guide to the Spiders of California and the Pacific Coast States" by R.J. Adams also show L. hesperus with the complete line and L. geometricus with some spots separate and more white wrapped around the lateral black spots ... still, given this is just a photo of a juvenile this is only an educated guess as they are similar and vary a lot.

I'm actually with you now. I think I was wrong.
Sorry for the hassle!

Moved from ID Request.

Not an expert, but..
I would think that it is a juvenile female, because I believe the males are harmless. The juveniles of both sexes look the same. As the female matures, her coloration changes becoming darker, matching the description you are familiar with.
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