Harlequin Bugs

These look like harlequin bug nymphs (immature bugs). Their scientific name is Murgantia histrionica. They are “true bugs” in the group called Stink Bugs. They can attack a variety of food plants/crops (all plant parts except roots) and ornamentals and can be very damaging in large numbers. Their true preference is plants in the brassica / mustard family. They are sap sucking insects (not chewing) so they make white spots on the leaves rather than holes or other chewed parts. Hand removal is effective; you can also use insecticides, but be sure to use something safe for edibles. Here’s a web link with more info:
http://nathistoc.bio.uci.edu/hemipt/Murgantia.htm
http://www.ipm.ucdavis.edu/PMG/GARDEN/VEGES/PESTS/harlequinbug.html