This past winter's rains have been wonderful for many plants, but also has encouraged some pests that perhaps were held back by the drought. I noticed the small shiny black bugs (ca. 3/8") about 2 months ago, but I wasn't sure what they were feeding on (not much sign of damage), or what they were.
They became very numerous and some developed red areas. Not exactly the Bagrada bug, but abundant like them. Then the chard developed huge holes. I also noticed some larger bugs - tan to light brown with rough looking wing covers, longish triangular shaped, with distinctive pale orange margins.
I started catching the black bugs by scraping them up into the cap of a jar which I had filled with soapy water, and tossing them into the water.
The museum entomology staffer said they were nymph stages and couldn't be identified.
Yesterday, I caught two copulating brown and orange margined adults, threw them in alcohol and thought at least I'd find out what they are. Eureka! Another entomology staffer found this website that had my mystery black bugs along with the very different adults. So they were one and the same! The adult is on p. 112 in Hogue's Insects of Los Angeles Basin. The website has the various stages.
They're Largus cinctus or Largus californicus (a more systematic individual will need to resolve whether they are one or two species, or a variety). You can call them the "Bordered Plant Bug". Innocuous name - but I'd start trapping them before they over-run your vegetables.