The apterae of Essigella californica are slender and spindle-shaped and ranges from about 1.5 - 2.0 mm long. They have very short 5-segmented antennae, which distinguishes them from species of Eulachnus aphids that have longer 6-segmented antennae. The thorax is grey-green and the abdomen pale lime green, and can have faint brown dorsal spots (but not always). The legs are pale but can range in colour, with the tibiae often darker than the rest of the leg. Abdominal tergites II-IV each have a transverse row of 6 spinopleural hairs, and 2 marginal hairs on each side. The adults can either be winged or wingless.