The Polyphemus Moth, Antheraea polyphemus, is one of the largest and most recognizable silk moths found in North America. This nocturnal insect belongs to the family Saturniidae. The moth’s common name comes from the Greek mythological cyclops, referencing the single, large eyespot on each of its hindwings. This article explores the current status of the Polyphemus Moth to determine its abundance and the factors that influence its presence across the continent.
Conservation Status and Abundance
The Polyphemus Moth is generally not considered rare from a continental perspective, as it is one of the most widely distributed silk moths in North America. Its overall conservation status is ranked as G5, meaning it is “Globally Secure” and common throughout its extensive range. This ranking indicates the species has a very low risk of extinction or collapse.
Despite this secure global status, the moth can be locally uncommon or fluctuate widely in certain areas. Federal agencies in the United States and Canada do not list the Polyphemus Moth as threatened or endangered. Its widespread distribution and ability to survive in various habitats contribute to its overall stability.
Geographic Distribution and Host Plants
The geographic range of the Polyphemus Moth is vast, extending across the majority of the continental United States, southern Canada, and northern Mexico. It is absent only from the extreme southwestern United States, specifically parts of Arizona and Nevada. This expansive distribution allows the species to occupy diverse environments, including forests, urban parks, orchards, and wetlands.
The presence of the moth is fundamentally tied to the availability of its food source, as the caterpillars are polyphagous, meaning they feed on a wide variety of plants. Common host plants include deciduous trees like oak, maple, willow, birch, elm, and hickory. Females lay eggs directly on the leaves of these host plants, ensuring the newly hatched larvae have an immediate food source.
Identifying the Polyphemus Moth
Adult Polyphemus Moths are large, with a wingspan that typically measures between 4 and 6 inches (10 to 15 cm). The wings range from reddish-brown to a pale tan or yellowish-brown, often with subtle pink and white lines along the margins. The moth’s body is robust and covered in soft, dense hair.
The most distinguishing feature is the set of large eyespots, or ocelli, present on all four wings. The eyespots on the hindwings are prominent, characterized by a clear, translucent center surrounded by concentric rings of yellow, blue, and black. The caterpillar is also notable, appearing as a large, bright apple-green grub that can grow up to four inches in length before pupating.
Factors Affecting Local Populations
While the Polyphemus Moth is globally secure, several factors can cause local numbers to drop significantly. One major concern is the introduced parasitoid fly, Compsilura concinnata, brought to North America to control the invasive spongy moth. This fly is a generalist, attacking a wide range of native caterpillars, including the Polyphemus Moth.
The fly lays its eggs directly on or inside the caterpillar; the larva then consumes the host, preventing it from reaching adulthood. This parasitism causes high mortality rates in local populations of native silk moths. This unintended consequence of biological control is a primary reason why these large moths are less frequently observed in some eastern regions.
Artificial light at night (ALAN) is another factor that disrupts the moth’s nocturnal life cycle. Adult Polyphemus Moths are strongly attracted to artificial lights, causing them to exhaust limited energy reserves and become easy targets for predators. Since adults do not feed, their brief lifespan is entirely dedicated to reproduction, making any disruption a serious threat to local survival.
Fragmentation of large, undisturbed wooded areas due to urbanization also puts pressure on local populations. Although the Polyphemus Moth is adaptable to suburban environments, the loss of contiguous forest patches reduces suitable habitat for both caterpillars and pupae. These combined pressures contribute to the perception that the Polyphemus Moth is much rarer than its official conservation status might suggest.