Moth

Moths, excluding butterflies, comprise all members of the order Lepidoptera that are not classified as butterflies. Although moths were once placed in the suborder Heterocera, this distinction is no longer used because it represents a paraphyletic grouping in contrast to the monophyletic Rhopalocera (butterflies). Today, moths represent the vast majority of Lepidoptera, with an estimated 160,000 described species and many more remaining unidentified. While most moths are nocturnal, significant numbers are crepuscular or even diurnal, reflecting considerable ecological diversity.

Differences Between Butterflies and Moths

Moths do not form a single natural evolutionary group, whereas butterflies constitute a clear monophyletic lineage. Earlier attempts to divide Lepidoptera into natural groups—such as Microlepidoptera versus Macrolepidoptera or Ditrysia versus Monotrysia—have proven problematic due to lack of monophyly. Nevertheless, several practical distinctions exist.
A key diagnostic feature is found in the antennae. Butterflies possess slender antennae ending in small clubs, with the exception of the Hedylidae, whereas moth antennae are typically feathery or filamentous and lack clubbed tips. The terms Rhopalocera (club-antennae) and Heterocera (varied-antennae) reflect this distinction. Lepidoptera first emerged during the Carboniferous period, but the distinctive proboscis evolved later in the Cretaceous alongside the rise of flowering plants.

Etymology

The modern English word moth derives from the Old English moððe, related to terms in Old Norse, Dutch and German with similar meanings. The root is possibly associated with the Old English moða, meaning maggot, or with midge, which until the sixteenth century referred primarily to larvae known for damaging textiles.

Caterpillars and Life Cycle

Moth larvae, commonly known as caterpillars, often spin cocoons of silk before emerging as adult moths. Some species pupate underground by digging burrows. Upon metamorphosis, the adult moth emerges with fully developed wings. The Poplar Hawk-moth (Laothoe populi), among others, demonstrates the typical Lepidopteran transformation from larva to pupa to adult.

Evolutionary History

Moths evolved long before butterflies, with fossil evidence indicating forms as old as 190 million years. Early ancestors, including Archaeolepis, show wing scales resembling those of caddisflies, suggesting a shared evolutionary heritage. The coevolution of Lepidoptera with angiosperms is well documented, as both larvae and adults rely heavily on flowering plants for nutrition.

Economic Significance

Agricultural and Forest Pests

Many moth species, particularly in their larval stages, are significant agricultural and forestry pests. Examples include:

• Corn borers and bollworms, which damage staple crops.
• The spongy moth (Lymantria dispar), a destructive invasive species in northeastern United States forests.
• The codling moth, a major pest in fruit orchards.
• The diamondback moth, a severe pest of Brassicaceae crops in tropical and subtropical regions.
• Eldana, a major threat to sugarcane, maize and sorghum in sub-Saharan Africa.

Clothes moths (family Tineidae) are known for damaging wool and other protein-based fibres. Only the larvae consume such materials; most adult moths do not feed on fabrics, and several large species lack functional mouthparts entirely, surviving solely on energy stored from their larval stage.

Preventing Infestation

Common textiles damaged by clothes moth larvae can be preserved through freezing at temperatures below –18°C. Traditional repellents such as lavender or cedar wood are considered of limited effectiveness, although naphthalene remains widely used, despite health concerns.

Silk Production

Several moth species are economically valuable for their silk. The domesticated silkworm (Bombyx mori) is the most important, producing over 130 million kilograms of raw silk annually. Other silk-producing species include:

• Samia cynthia (ailanthus moth)
• Antheraea pernyi (Chinese oak silkmoth)
• Antheraea assamensis (Assam silkmoth)
• Antheraea yamamai (Japanese silk moth)

Moth larvae are also harvested as a food source in many African regions. The mopane worm (Gonimbrasia belina) is a widely consumed example, and the larvae of numerous other species contribute significantly to local diets and economies.

Predators and Parasites

Moths form an essential part of many food webs and are preyed upon by bats, owls, other birds, lizards, amphibians, rodents, cats, dogs and even bears. Larvae are frequently parasitised by ichneumonid wasps and targeted by baculoviruses, which are used as biological control agents. Some moths have evolved acoustic defences: noctuids drop into sudden dives when detecting bat ultrasound, while arctiine moths emit ultrasonic clicks to disrupt bat echolocation.
Certain fungi, such as Ophiocordyceps sinensis, parasitise moth larvae, with significant ecological and cultural implications in parts of Asia.

Ecological Importance

Moths are vital nocturnal pollinators, often overlooked in comparison to bees and butterflies. They transfer pollen across a wide range of plant species, including many overlooked by daytime pollinators. Studies from the United Kingdom show moths carrying pollen from at least forty-seven plant species, several of which bees rarely visit.
Research from Himalayan ecosystems indicates that families such as Erebidae and Sphingidae may be key pollinators for some high-altitude flowering plants. Greater awareness of moth pollination is reshaping understanding of nocturnal ecological networks, suggesting that numerous plants previously assumed to be bee-pollinated may rely significantly on moths.

Attraction to Light

A well-known behaviour of moths is their attraction to artificial lights. The underlying cause remains debated, but the most widely discussed explanation is the celestial orientation hypothesis. Moths evolved to navigate by maintaining a fixed angle relative to the moon or other distant light sources. Artificial lights are too close for this method to function correctly, causing the moth to spiral inadvertently towards the light as it continuously attempts to correct its flight path.