The blue alfalfa aphid looks very much like the pea aphid. However, the blue alfalfa aphid is slightly smaller, more of a blue-green in color, and may have a waxy appearance. In contrast, the pea aphid is lighter green in color and shinier than the blue alfalfa aphid. The third antennal segment of the blue alfalfa aphid is uniformly brown; that of the pea aphid has a narrow dark band at the tip. The thoracic area on the winged forms of the blue alfalfa aphid is dark brown as opposed to light brown on the pea aphid.