The genus Deidamia encompasses a single recognized species, Deidamia inscriptum, known as the lettered sphinx moth. This insect is a member of the Sphingidae family, a group of moths often recognized for their robust bodies and rapid flight.
Identification and Physical Characteristics
The adult lettered sphinx moth has a wingspan ranging from 45 to 70 millimeters (1.75 to 2.75 inches). Its forewings display a cryptic blend of brown and gray tones, featuring deeply scalloped outer margins. Fine white lines or dark brown markings adorn these forewings, giving rise to the “lettered” part of its common name. The hindwings are a plain brown or orange-brown color. Males may hold their abdomens slightly curled upwards when at rest.
The larval stage, known as a hornworm, has a green body with yellow patterning along its sides. Caterpillars possess a characteristic horn-like structure on their posterior end, which is yellow with a black tip. Fully grown caterpillars reach lengths between 25 to 38 millimeters (1 to 1.5 inches).
Geographic Range and Habitat
The lettered sphinx moth is broadly distributed across eastern and central North America. Its range extends from southern Canada, including Ontario and Quebec, southward to Florida, and westward through states such as Texas, Minnesota, Nebraska, and Oklahoma.
This moth adapts to various environments. It is found in deciduous woodlands, forests, and thickets. Suburban areas, urban parks, wetlands, fields, and vineyards also serve as suitable habitats. The presence of ample food plants is a determining factor for its occurrence in these diverse settings.
Life Cycle and Behavior
The life cycle of Deidamia inscriptum begins when the female moth lays eggs on host plant leaves. Upon hatching, larvae (caterpillars) emerge and feed on foliage. Once fully grown, caterpillars descend to the ground to pupate, usually in the soil or leaf litter. The moth overwinters in this pupal stage.
The adult lettered sphinx moth is one of the earliest sphinx moths to emerge in its range. Adults fly in early spring, with periods spanning from March to June in most areas, though emergence can begin as early as February in southern regions like Louisiana. These moths are primarily nocturnal, showing a strong attraction to light sources. They have also been observed flying during daylight hours.
Host Plants and Diet
The diet of the lettered sphinx varies between its larval and adult stages. Caterpillars are herbivorous, feeding exclusively on plants from the grape family (Vitaceae). Their food sources include wild grape (Vitis), Virginia creeper (Parthenocissus quinquefolia), and ampelopsis (Ampelopsis). Larvae feed individually and are found resting on the undersides of leaves.
Adult lettered sphinx moths are nectar feeders. They use a long proboscis to access nectar from various early spring flowers. Nectar sources include common spring bloomers such as lilac (Syringa vulgaris) and Phlox. This nectar consumption provides energy for their flight and reproductive activities.