Lepidoptera migration

Many populations of Lepidoptera (butterflies or moths) migrate, sometimes long distances, to and from areas which are only suitable for part of the year. Lepidopterans migrate on all continents except Antarctica, including from or within subtropical and tropical areas. By migrating, these species can avoid unfavorable circumstances, including weather, food shortage, or over-population. In some lepidopteran species, all individuals migrate; in others, only some migrate.Tirumala septentrionisVanessa carduiAppias albinaCatopsilia pomonaEuploea coreEuploea sylvester Many populations of Lepidoptera (butterflies or moths) migrate, sometimes long distances, to and from areas which are only suitable for part of the year. Lepidopterans migrate on all continents except Antarctica, including from or within subtropical and tropical areas. By migrating, these species can avoid unfavorable circumstances, including weather, food shortage, or over-population. In some lepidopteran species, all individuals migrate; in others, only some migrate. The best-known lepidopteran migration is that of the eastern population of the monarch butterfly which migrates from southern Canada to wintering sites in central Mexico. In late winter/early spring, the adult monarchs leave the Transvolcanic mountain range in Mexico for a more northern climate. Mating occurs and the females begin seeking out milkweed to lay their eggs, usually first in northern Mexico and southern Texas. The caterpillars hatch and develop into adults that move north, where more offspring can go as far as central Canada until next migratory cycle. The Danaids in South India are prominent migrants, between the Eastern Ghats and Western Ghats. Three species will be involved in this, namely Tirumala septentrionis, Euploea core, and Euploea sylvester. Sometimes they are joined by lemon pansy (Junonia lemonias), common emigrant (Catopsilia pomona), tawny coster (Acraea terpsicore) and blue tiger (Tirumala limniace). Migration in Lepidoptera means a regular, predictable movement of a population from one place to another, determined by the seasons. There is no unambiguous definition of migratory butterfly or migratory moth, and this also applies to proposals to divide them into classes. Migration means different things to behavioral scientists and ecologists. The former emphasize the act of moving whereas the latter discriminate between whether the movement has been ecologically significant or not. Migration may be viewed as 'a behavioural process with ecological consequences'. Migration in Lepidoptera takes place in two of the three modes of migration identified by Johnson (Johnson, 1969). In the first mode (also Johnson's first), the Lepidoptera move in one direction in their short life-span and do not return. An example is the pierid butterfly, Ascia monuste, which breeds in Florida but sometimes migrates along the coast up to 160 kilometers to breed in more suitable areas. In the second mode (Johnson's third), migration takes place to a place of hibernation or aestivation where they undergo diapause and the same generation survives to return. The classic example is that of the nymphalid monarch butterfly (Danuas plexippus). Species that are recorded in unexpected areas (adventive species) are not considered to be migratory species, because these did not leave their habitat on their own strength. Examples are species that are imported as egg or caterpillar alongside of their host plants or individuals that were reared by a collector but have escaped. An example of an introduced species is Galleria mellonella, which is found all over the world, because it is reared as food for captive birds and reptiles. At times it is difficult to decide if a species is adventive or migratory. Migratory species like Chrysodeixis chalcites and Helicoverpa armigera would be able to reach western Europe on their own, but are also common in greenhouses. Lepidoptera migration is often seasonal. With species of which all individuals migrate, the population moves between areas in the summer and winter season or the dry and wet season. For species of which only part of the population migrates, seasonal migration is hard to determine. They can maintain themselves in part of their habitat but also reach areas where they cannot establish a permanent population. They only live there in the season that is most favorable for the species. Some of the species have the habit of returning to their permanent residence at the end of the season.