Moths, a diverse group of insects with over 160,000 described species globally, often spark curiosity regarding their dietary habits. A common misconception is whether these nocturnal creatures are omnivores, consuming both plant and animal matter. The feeding behaviors of moths are varied, depending significantly on the species and their life stage.
Understanding Moth Diets
The vast majority of moths are herbivores, primarily consuming plant-based materials. Adult moths typically feed on liquids, which they draw using a specialized, straw-like mouthpart called a proboscis. Common liquid food sources include nectar from flowers, sugary juices from ripe or fermenting fruits, and tree sap. This liquid diet provides them with the sugars and energy necessary for flight and reproductive activities.
Many adult moths also play a role in pollinating flowers as they feed on nectar. They can consume honeydew, a sugary liquid excreted by aphids, and some are attracted to decaying organic matter like carrion or fungi. Despite some rare exceptions, the predominant diet across the order Lepidoptera, which includes moths, is herbivorous.
Dietary Variations Across Life Stages
Moths undergo complete metamorphosis, meaning their diet changes significantly throughout their life cycle. The larval stage, known as a caterpillar, is when most feeding occurs. Caterpillars possess chewing mouthparts, called mandibles, which enable them to consume solid plant material such as leaves, stems, and roots. Many caterpillar species are highly specialized, feeding exclusively on specific host plants.
After consuming enough energy, a caterpillar pupates and emerges as an adult moth. While most adult moths consume liquids, some, like the Luna moth or Hercules moth, do not feed at all during their short adult lifespan. These non-feeding adults rely solely on energy reserves accumulated during their voracious caterpillar stage, often possessing vestigial or absent mouthparts.
Specialized Moth Diets and Exceptions
While most moths are herbivores, some species exhibit specialized or unusual feeding habits. Certain moth caterpillars are detritivores, feeding on decaying organic matter like fungi, lichens, or animal products such as fur, hair, and feathers. Clothes moth caterpillars, for example, consume natural fibers like wool and silk, which contain protein and keratin.
Rare carnivorous moth larvae exist, preying on other insects or even other caterpillars. An unusual example is the gopher tortoise moth caterpillar (Ceratophaga vicinella), which feeds exclusively on keratin from dead gopher tortoise shells. Among adult moths, some exceptions include species that feed on pollen, while others, such as certain Calyptra species (often called “vampire moths”), pierce the skin of mammals, including humans, to feed on blood or other bodily secretions like tears. This unusual blood-feeding behavior in male Calyptra moths is thought to provide sodium, which can be passed to females to support the development of their offspring.