Adults are primarily brown, with contrasting white bands on the abdomen. There is a distinct, broad white band on the hindwings, and white markings on the edges of the hindwing and forewing. The top side of the antenna has white striping.

The larva is smooth and fleshy, with multi-colored markings of green, orange, pink, white and black. There is a short horn or spur near its hind end.

The Kern primrose sphinx moth has a streamlined, yet stout body, and elongate forewings that are slanted at the outer margins.

Measurements
Wingspan: Up to 3 in

Larvae feed exclusively on the leaves of their host plants, evening primroses, suncups and related species (Camissonia spp.). Adults feed on the nectar of a variety of flowers, including filaree (Erodium spp.), goldfields (Lasthenia chrysostoma), baby blue-eyes (Nemophila menziesii) and miniature lupine (Lupinus bicolor).

Females lay tiny, 0.04 to 1.0 inch (0.1 centimeter), light green eggs on their host and surrounding plants. Larvae emerge from the eggs a few days later and begin to feed, traveling to the host plant if necessary. When larvae are ready to pupate, they bury themselves underground, 2 to 4 inches deep. High humidity is required for this species to develop in the pupa. Adults will emerge when humidity and temperatures are both high enough, beginning in early spring. Flight periods for the adults range from late February to early April. Pupae are known to diapause, meaning that they delay metamorphosis to adult form, underground for multiple years during drought periods.

Pupae may lay dormant for several years underground before metamorphizing into adults. Adult life span is unknown for this species. 

The larval host plant, which is related to evening primrose (Camissonia) of this species, grows in dry, disturbed, sandy-gravelly areas like sandy washes next to fields.