Larvae emerge from the eggs about a week after oviposition and begin to feed on the flowers and young leaves of the evening primrose.

First-instar larvae (caterpillar phases) are green with dark brown to black heads, legs, lateral spiracles, thoracic shields, and blunt anal horns.

The adult's flight season occurs from mid-January to the first week of April, with a peak period in mid-February through mid-March.

More specifically, the moth favors the banks of sandy washes, in which the sand has the proper compaction and moisture content for burrowing larvae.

It once was believed that Erodium was a serious threat to the sphinx moth because of larval mortality after eggs were mistakenly deposited on this plant.

However, emerging research shows that female moths deposit eggs on plants indiscriminately, and the larvae wander to find a suitable host.