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|Emperor Gum Moth, Opodiphthera eucalypti|
|Emperor Gum Moth, Opodiphthera eucalypti|
A moth is an insect related to the butterfly, both being of the order Lepidoptera. Most of this order are moths; there are thought to be approximately 160,000 species of moth (nearly ten times the number of species of butterfly), with thousands of species yet to be described. Most species of moth are nocturnal, but there are crepuscular and diurnal species.
Moths are not easily differentiated from butterflies. Sometimes the name "Heterocera" is used for moths while the term "Rhopalocera" is used for butterflies to formalize the popular distinction; these, however, have no taxonomic validity. Many attempts have been made to subdivide the Lepidoptera into groups such as the Microlepidoptera and Macrolepidoptera, Frenatae and Jugatae, or Monotrysia and Ditrysia. Failure of these names to persist in modern classifications is because none of them represents a pair of monophyletic groups. Butterflies can be classified within the "moths" (being considered as part of Ditrysia of the Neolepidoptera). There is thus no way to group all of the remaining taxa in a monophyletic group, as it will always exclude that one descendant lineage.
The Modern English word "moth" comes from Old English "moððe" (cf. Northumbrian "mohðe") from Common Germanic (compare Old Norse "motti", Dutch "mot" and German "Motte" all meaning "moth"). Perhaps its origins are related to the Old English "maða" meaning "maggot" or from the root of "midge" which until the 16th century was used mostly to indicate the larva, usually in reference to devouring clothes.
The study of butterflies and moths is known as lepidoptery, and biologists that specialize in either are called lepidopterists. As a pastime, watching butterflies and moths is known as butterflying and mothing. The latter has given rise to the term "mother" for someone who engages in this activity - sometimes written with a hyphen (moth-er) to distinguish it from the more common word of the same spelling. This confusion does not arise in speech as it is pronounced differently (//, not *//).
Moth larvae, or caterpillars, make cocoons from which they emerge as fully grown moths with wings. Some moth caterpillars dig holes in the ground, where they live until they are ready to turn into adult moths.
Moths, and particularly their caterpillars, are a major agricultural pest in many parts of the world. Examples include corn borers and bollworms. The caterpillar of the gypsy moth (Lymantria dispar) causes severe damage to forests in the northeast United States, where it is an invasive species. In temperate climates, the codling moth causes extensive damage, especially to fruit farms. In tropical and subtropical climates, the diamondback moth (Plutella xylostella) is perhaps the most serious pest of brassicaceous crops.
Several moths in the family Tineidae are commonly regarded as pests because their larvae eat fabric such as clothes and blankets made from natural proteinaceous fibers such as wool or silk. They are less likely to eat mixed materials containing artificial fibers. There are some reports that they can be repelled by the scent of wood from juniper and cedar, by lavender, or by other natural oils. However, many consider this unlikely to prevent infestation. Naphthalene (the chemical used in mothballs) is considered more effective, but there are concerns over its effects on human health. Moth larvae may be killed by freezing the items which they infest for several days at a temperature below −8 °C (18 °F).
Some moths are farmed. The most notable of these is the silkworm, the larva of the domesticated moth Bombyx mori. It is farmed for the silk with which it builds its cocoon. As of 2002[update], the silk industry produces over 130 million kilograms of raw silk, worth about 250 million U.S. dollars, each year. Not all silk is produced by Bombyx mori. There are several species of Saturniidae that are also farmed for their silk, such as the Ailanthus moth (Samia cynthia group of species), the Chinese Oak Silkmoth (Antheraea pernyi), the Assam Silkmoth (Antheraea assamensis), and the Japanese Silk Moth (Antheraea yamamai).
The mopane worm, the caterpillar of Gonimbrasia belina, from the family Saturniidae, is a significant food resource in southern Africa. Despite being notorious for eating clothing, most moth adults do not eat at all. Most like the Luna, Polyphemus, Atlas, Prometheus, Cecropia, and other large moths do not have mouths. When they do eat, moths will drink nectar.
Nocturnal insectivores often feed on moths; these include some bats, some species of owls and other species of birds. Moths are also eaten by some species of lizards, cats, dogs, rodents, and some bears. Moth larvae are vulnerable to being parasitized by Ichneumonidae.
Baculoviruses are parasite double-stranded DNA insect viruses that are used mostly as biological control agents. They are members of the Baculoviridae, a family that is restricted to insects. Most baculovirus isolates have been obtained from insects, in particular from Lepidoptera.
There is evidence that ultrasound in the range emitted by bats causes flying moths to make evasive maneuvers because bats eat moths. Ultrasonic frequencies trigger a reflex action in the noctuid moth that cause it to drop a few inches in its flight to evade attack. Tiger moths also emit clicks which foil bats' echolocation.
Moths frequently appear to circle artificial lights, although the reason for this behavior remains unknown. One hypothesis to explain this behavior is that moths use a technique of celestial navigation called transverse orientation. By maintaining a constant angular relationship to a bright celestial light, such as the Moon, they can fly in a straight line. Celestial objects are so far away, that even after travelling great distances, the change in angle between the moth and the light source is negligible; further, the moon will always be in the upper part of the visual field or on the horizon. When a moth encounters a much closer artificial light and uses it for navigation, the angle changes noticeably after only a short distance, in addition to being often below the horizon. The moth instinctively attempts to correct by turning toward the light, causing airborne moths to come plummeting downwards, and resulting in a spiral flight path that gets closer and closer to the light source.
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