Our best guess for this immature bug (nymph) is a Conchuela Bug. These stink bugs come in a range of colors—olive-green, brown, gray, or black, with southern populations darker across their western North America range. This individual will become less rounded and develop two pairs of wings as it grows. All stages dine on fruits and seeds, including beans, alfalfa, and blackberries. Adults overwinter and come out in spring to feed, mate, and lay eggs.
Photo by: Rose Marchak on 8/14/21 in Missoula, MT