The Polyphemus moth, Antheraea polyphemus, is one of North America’s largest and most visually striking insects, recognizable by its impressive wingspan (up to six inches) and the prominent eyespots on its hindwings. This giant silk moth belongs to the family Saturniidae. Its life cycle involves a dramatic contrast in nutritional needs, shifting from intense, non-stop feeding as a caterpillar to an adult stage that consumes nothing at all.
The Diet of the Polyphemus Caterpillar
The Polyphemus caterpillar is the only stage in the moth’s life cycle that consumes food, and its appetite is immense. Newly hatched larvae begin feeding immediately, passing through five growth stages (instars) and rapidly increasing their mass. The larva is a bright, translucent green color, eventually growing up to three to four inches long before pupating.
As a generalist feeder, the caterpillar is polyphagous, meaning it feeds on a wide array of host plants rather than specializing in a single species. Its diet consists entirely of the leaves of numerous deciduous trees and shrubs.
The host plants include:
- Oak
- Maple
- Birch
- Willow
- Cherry
- Plum
- Hickory
This period of voracious consumption serves the purpose of storing energy reserves. The caterpillar must accumulate enough fat and nutrients to power its complete metamorphosis and sustain its entire adult life. A Polyphemus larva can consume hundreds of times its own weight in leaves during the few weeks it spends feeding. This stored energy fuels the subsequent adult stage.
Why Adult Polyphemus Moths Do Not Eat
The adult Polyphemus moth does not consume any food or liquids throughout its entire winged lifespan. This non-feeding behavior is a result of a biological adaptation common among the giant silk moth family. The adult possesses vestigial mouthparts, meaning the structures necessary for eating have become non-functional or atrophied during metamorphosis.
Specifically, the moth lacks a proboscis, the long, tube-like structure many other moth and butterfly species use to sip nectar or other fluids. Without functional mouthparts, the adult is physically incapable of ingesting any form of sustenance. Its short existence, which typically lasts only seven to ten days, is solely dedicated to reproduction.
The moth relies completely on the substantial fat reserves accumulated by the caterpillar to fuel its brief reproductive flight, including the energy needed for the male to locate a female and for the female to lay eggs. This biological strategy prioritizes rapid mating and egg-laying over prolonged survival. The adult stage functions purely as a mobile vessel for genetic exchange, using up all its stored resources.