Also called white-margined burrowing bug, for good reason as you can see in this great shot by Barry. These tiny bugs (about 5 mm) are found most often nectaring on flowers, but they are completely harmless, to you and to your flowers and should be left alone. These little guys will overwinter underneath leaf litter. You are most likely to find them if you have plants in the mint family in your garden, as these are their larval plants of choice, the larvae being fed the seeds of such plants.