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.
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.
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.
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.
Migratory species like Chrysodeixis chalcites and Helicoverpa armigera would be able to reach western Europe on their own, but are also common in greenhouses.
It is thought that Vanessa atalanta produces enough body warmth during flight since it has also been recorded migrating at night.
In the case of transcontinental migration where distances are large, the flying speed of the butterfly (of the order of 3 metres per second or less) is inadequate for timely completion of journey.
[10] For example, the painted lady (Vanessa cardui) migrates from Africa to Spain aided by tail winds.
The small diamondback moth is also a migratory species that migrates 3,000 kilometers and can be found up to altitudes of 100 meters or more.
[14] Tests have been performed to interfere with the biological clock of certain species by keeping them in the dark and then observing if they would choose for other flight paths.
[18] A study in Panama of Aphrissa statira, which migrate in large groups annually, found that this species loses its navigational capacity when exposed to a magnetic field, suggesting they use the Earth's magnetic field to determine their direction of flight in migration.
Genetic analysis of pollen grains transported by hundreds of butterflies collected across ten countries allowed researchers to track down the origin of a migration event that took place over 9 months from 2018 to 2019.
Most likely, the butterfly outbreak originated in northern Arabia and the Middle East, when vegetation was unusually abundant in late 2018 to early 2019.
Examples of this are a shortage of proper food plants, an unfavorable climate, like cold or extreme rain or overpopulation.
[37] Butterflies (and to a lesser extent moths) migrating in large numbers are a noteworthy sight, which is easy to observe and track.
Global warming has caused an increase of migratory butterflies and moths that reach north-western European countries like the Netherlands, Belgium and the United Kingdom.
Dwindling numbers and the following decline of ecosystems will lead to greater loss of biological wealth over time, as without pollinators many plants will not grow or bloom.
The causes of the recent decline are lodging, falling trees, global warming, reduction of milkweed to breeding places, and the drought in areas butterflies roost.
Some examples of threatened or endangered American butterflies include: The solutions are simple, the include but are not limited to educational material to educate young children, The Monarch Act of 2021, butterfly sanctuaries, limiting the use of pesticides and herbicides while farming, and planting the native milkweed.
