Insect and Spider Identification: I've been invaded! By what..?, 1 by Triona

Triona wrote:
These little flying critters have arrived in swarms over the past week... they are on everything... and seem to be devouring my green beans, basil, lettuce, borage, & cilantro... they're tiny, maybe 1/8-1/16 of an inch & speedy as heck. They take off upon approach, or with the slightest disturbance... ideas as to what they are, if they'll cause major damage to my garden... & any preventative measures? Thanks!!