The Sphingidae are strong fliers, with a rapid wingbeat. Most are medium to large moths, with heavy bodies; wingspread reaches 5 inches or more in some species. Although a few are active in the daytime, most species in the group are active at dusk. Most, but not all, sphingids feed much like hummingbirds, hovering in front of a flower and sipping nectar through the extended proboscis. The proboscis rolls up like a party noisemaker when not in use, and may not be readily evident in a resting moth. Some species lack scales on large portions of their wings, and therefore have transparent or clear wings. These are commonly referred to as "clearwing hummingbird moths," (Note however that the scientifically accepted common name of "Hummingbird clearwing" refers specifically to Hemaris thysbe.)
Yet another common name for the group is "hornworms." The name comes from a hook or hornlike appendage protruding upward near the posterior end of the caterpillar (larval stage) of most species. Although the horn looks like it may be dangerous, it is in fact harmless. Unfortunately, the larval stage of some species can be very destructive to agricultural crops and ornamental plantings. The tomato hornworm, for example, feeds on potato, tomato and tobacco plants, and can cause severe economic loss in these crops.