The ones in our gardens are called
Leptoglossus clypealis
This site isn't that long and explains anything you would want to know about them.
http://ipm.ucanr.edu/PMG/PESTNOTES/pn74168.html
They like tomatoes, and cited from the above site "They are closely related to other sucking insects, such as stink bugs (family Pentatomidae) that can also suck juices from plants."
They showed up yesterday, and they will fly at your head. They also like to hang out in groups...maybe they should have named them 'Teenager Bugs'.
Don't let the ugly tomato plant scare you.