In this case the natives are insects native to Africa, who have decided that California is the place they ought to be. The Bagrada Bug arrived in Southern California just 6 years ago and already had decides to move north. The experts were hoping the colder winters might kill them off, but they decided to hide in the top layers of soil during winter. Come spring they emerge to eat stuff like "cabbage, kale, cauliflower, Brussels sprouts and broccoli, but they don't appear to be picky eaters. They have been known to feed on a wide variety of garden vegetables in California, including green beans, cantaloupe, corn, peppers, potatoes, tomatoes and sunflower. Even landscape plants are not immune. Bagrada bugs have been found feeding on ornamental plants in the mustard family, like sweet alyssum, stock and candytuft."
From the comment section at The Yolo county extension service, "I am a Master Gardener in LA County, managing a vegetable garden in The City of Bell. Bagrada bug has massively taken over arugula and to a lesser degree, Kale. I tried soapy water spray and pinching but could not keep up with them. Now I vacuum these crops on an almost daily basis with a hand held dust buster. WOW! I get hundreds every day and it is pretty quick to do. I have ordered some stink bug traps and will bait them with alyssum. I think that between the two controls, I MAY be able to grow greens this fall without a huge infestation."