The Polyphemus moth, a large silk moth native to North America, is recognized by its purplish eyespots on its hindwings. With an average wingspan of 15 cm (6 inches), this species is widespread across the continent, from subarctic Canada to Mexico. Like many insects, the Polyphemus moth undergoes a complete metamorphosis, transitioning through distinct stages: egg, larva (caterpillar), pupa, and adult. The dietary needs of this creature change significantly across these life stages, a key aspect of its survival.
The Caterpillar’s Diet
The larval stage, or caterpillar, is the primary feeding period for the Polyphemus moth. Newly hatched caterpillars are tiny and yellow, consuming vast quantities of leaves. They are considered polyphagous, meaning they feed on a wide variety of plants.
Common host plants include deciduous trees and shrubs. These include oak, maple, birch, willow, elm, and hickory. Fruit trees such as cherry, plum, and pear also serve as suitable food sources for these larvae.
As caterpillars grow, they undergo five molts (instars), shedding their skin to accommodate increasing size. During their final instar, they become bright green and can reach lengths of 3 to 4 inches. This rapid growth is fueled by their voracious appetite; a caterpillar can consume 86,000 times its emergence weight in less than two months.
Extensive feeding during this stage is crucial for accumulating energy reserves. These reserves are stored as fat, providing fuel for metamorphosis and sustaining the non-feeding adult moth. Caterpillars often remain on their host plants, feeding heavily until they are ready to spin their silk cocoons, often wrapped in leaves.
The Adult Moth’s Non-Diet
Unlike the caterpillar, the adult Polyphemus moth does not feed at all. The adult moth possesses vestigial mouthparts, which are underdeveloped and non-functional for eating. This means the adult moth relies entirely on energy reserves accumulated during its caterpillar stage.
The adult Polyphemus moth’s sole purpose is reproduction. Having no need to seek food, their brief adult life is dedicated to finding a mate and laying eggs. This non-feeding nature contributes to their short lifespan, which typically ranges from less than a week to about two weeks.
During this short period, females emit pheromones to attract males, who can detect these chemical signals from miles away using their feathery antennae. After mating, females lay their eggs on the leaves of host plants, initiating the next generation’s life cycle. The energy stored as a caterpillar is enough to complete these reproductive tasks before the adult moth’s life cycle concludes.