Adults range in size (1/6-1/3-inch long) and have dark bodies with bulging eyes on the sides of their head and cream-colored margins around the abdomen (but should not be confused with the beneficial insect, minute pirate bug, which also has bulging eyes). The forewings are dark and relatively slender compared to other true bugs. Immature black grass bugs are smaller than the mature adults, and lack wings.
Feeding damage from black grass bugs on wheat causes yellow or white spots at the feeding sites. Heavy infestations causes plants to appear 'speckled' or frosted and can result in poor grain fill.