Moths are a group of winged insects of the order Lepidoptera, the other well-known members of which are butterflies; they are characterized by dark or dull patterned wings. They were previously classified as suborder Heterocera, but the group is paraphyletic with respect to butterflies (suborder Rhopalocera) and neither subordinate taxon is used in modern classifications. Moths make up the vast majority of the order. There are approximately 160,000 species of moth, many of which have yet to be described. Most species of moth are nocturnal, although there are also crepuscular and diurnal species. Moths have a multi-stage life cycle, and undergo complete metamorphosis. Winged adults generally lay eggs on or near plant foliage on which their larvae, known as caterpillars, will feed. Although most feed on plant matter, some species such as Eupithecia orichloris are carnivorous insectivores. The caterpillars grow, sometimes very rapidly, and when fully developed will pupate, often after constructing a cocoon from silk. When metamorphosis is complete, the pupal skin splits, the adult insect climbs out and slowly expands its wings to dry and harden, before flying off. Moths are commonly thought to eat clothes and fabrics, however it is only their larvae, caterpillars, which may consume natural fibres. Moths are very widely distributed across diverse terrestrial habitats and are found on all continents except Antarctica.
Etymology 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'). Its origins are possibly 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.
Taxonomy
Among the Lepidoptera, moths comprise about 90% (remaining 10% being butterflies). There are around 160,000 described species. There is estimated to be tens of thousands of unidentified species, especially from tropical regions. The name Heterocera is no longer used in modern classification, however the name is often used to refer to moths; as Rhopalocera is like-wise used as the name for butterflies. Among the 125 known families, moths make up 118 of the Lepidoptera families, comprising all but the seven butterfly families. While there are 160,000 species described currently, the total number is estimated to be around 500,000. On average, over 1,000 species of Lepidoptera is described annually in recent years. Some of the largest moth families include Erebidae, Noctuidae, Geometroidea, and Pyralidae.
Differences between butterflies and moths
While the butterflies form a monophyletic group, the moths, comprising the rest of the Lepidoptera, do not. Many attempts have been made to group the superfamilies of the Lepidoptera into natural groups, most of which fail because one of the two groups is not monophyletic: Microlepidoptera and Macrolepidoptera, Heterocera and Rhopalocera, Jugatae and Frenatae, Monotrysia, and Ditrysia. Although the rules for distinguishing moths from butterflies are not well established, one very good guiding principle is that butterflies have thin antennae and (with the exception of the family Hedylidae) have small balls or clubs at the end of their antennae. Moth antennae are usually feathery with no ball on the end. The divisions are named by this principle: "club-antennae" (Rhopalocera) or "varied-antennae" (Heterocera). Lepidoptera first evolved during the Carboniferous period, but only evolved their characteristic proboscis alongside the rise of angiosperms in the Cretaceous period. Moths also tend to have far more hair-like scales than butterflies. Moths are usually nocturnal flyers in contrast to butterflies which fly by day, however there are many exceptions such as the Cinnabar moth.
Life cycle and description
Being oviparous, moth larva hatch as eggs. Female moths will usually nurture the eggs with a layer of nutrients, sometimes providing a protective chemical layer, or covering with urticating hairs (such as in Lymantriinae). Eggs vary in shape and size, some being very elongated, and in colour, some being well camouflaged, others being brightly coloured to indicate a chemical defence (aposematism).
Caterpillar
Moth larvae, or caterpillars, are the first life stage after emergence from the egg. During emergence from the egg larva will consume the egg shell. Larvae have sclerotized heads, and mouthparts adapted for chewing. They have very short antennae and stemmata, mainly used for food detection. They possess a spinneret for producing silk. The larval stage varies in duration depending on temperature and food availability, but usually takes from four to eight weeks, sometimes as short as two weeks. Species which enter diapause during the winter may take up to 10 months, some species may take years. Larvae have three pairs of thoracic legs, and multiple proleg with gripping hooks called crochets, and will walk in order to reach a suitable spot for pupation, and to reach food. The larval stage is the main feeding stage, where the larva will in most species consume plant matter. At the end of their life stage, caterpillars will seek out a location to enter the pupal stage. Usually this will be underground, or beneath plant debris. Most species are quite specific around where they will choose to pupate. Some species will pupate without constructing a cocoon, others will construct a cocoon from silk, often also incorporating plant debris, such as Cerura vinula which may incorporate pieces of chewed bark into the silk cocoon.
Pupa During the pupal stage, the pupa will undergo metamorphosis and will be immobile for the duration of the life stage. The outer shell of the Pupa is sclerotised, and usually shiny and smooth. At the end of this life stage, the pupa will emerge usually at specific times of the day, for instance in night flying moths usually late afternoon, in day flying usually early morning. To break free from the cocoon some species may secrete potassium hydroxide from their mouth to weaken the silk.
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