Hyalophora

Distinguished from other Saturniidae genera by combination of large size, specific wing pattern elements (particularly the structure and coloration of eyespots), and geographic distribution. Hyalophora cecropia can be distinguished from H. columbia by wing coloration and pattern details, and from H. euryalus by the latter's more western distribution and different host plant associations. Males identified by prominently feathery antennae; females by larger body size relative to wingspan and simpler antennae. Larvae identified by the distinctive color progression through instars and the prominent, colorful tubercles in final instar.

Deciduous and mixed forests, woodlands, and suburban areas with sufficient tree cover. Larval habitat determined by host plant distribution; adults often found near lights or in mating aggregations on vegetation.

North America, with species distributed across Canada and the United States. Hyalophora cecropia ranges from Nova Scotia and Maine west to the Rocky Mountains and south to Florida and Texas. H. columbia occurs in northern regions and mountainous areas. H. euryalus is western, occurring from British Columbia to California and east to the Rocky Mountains. H. gloveri occurs in the southwestern United States and Mexico.

Adults emerge in spring and early summer, typically May through July depending on species and latitude. Single generation per year (univoltine) throughout most of range; some southern populations may exhibit partial second generations. Overwintering stage is the pupa within the cocoon.

Larvae feed on leaves of a wide variety of woody plants. Documented host plants include maple (Acer), birch (Betula), cherry (Prunus), apple (Malus), ash (Fraxinus), willow (Salix), lilac (Syringa), and viburnum (Viburnum), among others. Adults do not feed; they rely on fat reserves accumulated during larval development.

• Acer - larval food plantMaples, primary host for H. cecropia
• Betula - larval food plantBirches
• Prunus - larval food plantCherries and plums
• Malus - larval food plantApple
• Fraxinus - larval food plantAsh
• Salix - larval food plantWillows
• Syringa - larval food plantLilac
• Viburnum - larval food plantViburnums

Complete metamorphosis (holometabolous). Eggs laid in clusters on host plant leaves. Larvae hatch and progress through five instars, with dramatic color changes at each molt. Final instar larvae spin large silken cocoons attached to branches or among leaves; pupation occurs within. Adults emerge following winter diapause, with emergence triggered by temperature and photoperiod cues. Mating occurs shortly after emergence; females deposit eggs and die within days to weeks.

Adults are nocturnal and strongly attracted to light sources. Males locate females using their enlarged, feathery antennae to detect sex pheromones released by females. Mating pairs may remain coupled for extended periods. Larvae are solitary feeders. When attacked, larvae of H. cecropia exhibit thrashing movements and regurgitate acidic gut contents (pH 1–2) as a chemical defense; this defensive behavior is reduced during and immediately after molting.

Larvae function as herbivores, consuming significant quantities of leaf material. Adults serve as prey for birds, bats, and other insectivores. Pupae in cocoons are consumed by some vertebrate predators. The genus has been impacted by introduced biological control agents, specifically the parasitic fly Compsilura concinnata, which was introduced to control gypsy moth populations but has caused significant declines in Hyalophora populations in parts of New England.

Subject of significant public interest due to large size and striking appearance; frequently photographed and celebrated in natural history media. Historical interest in silk production, though not commercially exploited. Used in research on insect development, endocrinology, and cell biology. Populations have declined in parts of range due to parasitism by introduced Compsilura concinnata, habitat loss, and light pollution. H. cecropia is the state insect of several U.S. states.

• Actias lunaLuna moth shares large size and eyespot patterning, but has elongated hindwing tails and pale green coloration not seen in Hyalophora; larvae differ in having fewer, less prominent tubercles.
• Antheraea polyphemusPolyphemus moth is similarly large with eyespots, but has more translucent wings with less complex patterning and lacks the multiple colored tubercles of Hyalophora larvae.
• Callosamia prometheaPromethea moth overlaps in range and size, but adults are more uniformly colored (often reddish-brown or tan) with less elaborate eyespots; larvae have different tubercle arrangement and coloration.

• Saturniidae
• giant silk moth
• cecropia
• North America
• forest
• nocturnal
• non-feeding adult
• univoltine
• introduced parasitoid impact
• research model organism

• BugGuide
• Wikipedia
• GBIF taxonomy match
• iNaturalist taxon
• NCBI Taxonomy
• Catalogue of Life
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