page_title: Lepidoptera
section_title: Polymorphism
hierarchical_section_title: Lepidoptera / Polymorphism
caption_attribution_description: English: Adult Bagworm moths (T. ephemeraeformis) mating
context_page_description: Lepidoptera is an order of insects that includes butterflies and moths. About 180,000 species of the Lepidoptera are described, in 126 families and 46 superfamilies, 10 per cent of the total described species of living organisms. It is one of the most widespread and widely recognizable insect orders in the world. The Lepidoptera show many variations of the basic body structure that have evolved to gain advantages in lifestyle and distribution. Recent estimates suggest the order may have more species than earlier thought, and is among the four most speciose orders, along with the Hymenoptera, Diptera, and Coleoptera.
  Lepidopteran species are characterized by more than three derived features. The most apparent is the presence of scales that cover the bodies, wings, and a proboscis. The scales are modified, flattened "hairs", and give butterflies and moths their wide variety of colors and patterns. Almost all species have some form of membranous wings, except for a few that have reduced wings or are wingless. Mating and the laying of eggs are carried out by adults, normally near or on host plants for the larvae.
context_section_description: Polymorphism is the appearance of forms or "morphs", which differ in color and number of attributes within a single species. In Lepidoptera, polymorphism can be seen not only between individuals in a population, but also between the sexes as sexual dimorphism, between geographically separated populations in geographical polymorphism, and between generations flying at different seasons of the year (seasonal polymorphism or polyphenism). In some species, the polymorphism is limited to one sex, typically the female. This often includes the phenomenon of mimicry when mimetic morphs fly alongside nonmimetic morphs in a population of a particular species. Polymorphism occurs both at specific level with heritable variation in the overall morphological adaptations of individuals, as well as in certain specific morphological or physiological traits within a species.
  Environmental polymorphism, in which traits are not inherited, is often termed as polyphenism, which in Lepidoptera is commonly seen in the form of seasonal morphs, especially in the butterfly families of Nymphalidae and Pieridae. An Old World pierid butterfly, the common grass yellow (Eurema hecabe) has a darker summer adult morph, triggered by a long day exceeding 13 hours in duration, while the shorter diurnal period of 12 hours or less induces a paler morph in the postmonsoon period. Polyphenism also occurs in caterpillars, an example being the peppered moth, Biston betularia.
  Geographical isolation causes a divergence of a species into different morphs. A good example is the Indian white admiral Limenitis procris, which has five forms, each geographically separated from the other by large mountain ranges. An even more dramatic showcase of geographical polymorphism is the Apollo butterfly (Parnassius apollo). Because the Apollos live in small local populations, thus having no contact with each other, coupled with their strong stenotopic nature and weak migration ability, interbreeding between populations of one species practically does not occur; by this, they form over 600 different morphs, with the size of spots on the wings of which varies greatly.
  Sexual dimorphism is the occurrence of differences between males and females in a species. In Lepidoptera, it is widespread and almost completely set by genetic determination. Sexual dimorphism is present in all families of the Papilionoidea and more prominent in the Lycaenidae, Pieridae, and certain taxa of the Nymphalidae. Apart from color variation, which may differ from slight to completely different color-pattern combinations, secondary sexual characteristics may also be present. Different genotypes maintained by natural selection may also be expressed at the same time. Polymorphic and/or mimetic females occur in the case of some taxa in the Papilionidae primarily to obtain a level of protection not available to the male of their species. The most distinct case of sexual dimorphism is that of adult females of many Psychidae species which have only vestigial wings, legs, and mouthparts as compared to the adult males that are strong fliers with well-developed wings and feathery antennae.
caption: Sexually dimorphic bagworm moths (Thyridopteryx ephemeraeformis) mating: The female is flightless.
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