Black widows are usually out of sight during the daytime. These timid spiders build irregular tangled webs, called cobwebs, in which they normally hang upside down so the hourglass on the underside of the abdomen is apparent although not always this obvious (it may be shaped differently or be fragmented). Immatures have red and white flame-like racing stripes on the top and sides of their abdomens. Adults (males and some females) retain these markings. I think this is the Southern Black Widow but Jackman (see references) indicates that the Western Black Widow is more likely in this area.
Same individual as shown above but photographed from the side.
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