Lepidoptera migration
Encyclopedia
Lepidoptera migration is a biological phenomenon whereby populations of butterflies
Butterfly
A butterfly is a mainly day-flying insect of the order Lepidoptera, which includes the butterflies and moths. Like other holometabolous insects, the butterfly's life cycle consists of four parts: egg, larva, pupa and adult. Most species are diurnal. Butterflies have large, often brightly coloured...
or moth
Moth
A moth is an insect closely related to the butterfly, both being of the order Lepidoptera. Moths form the majority of this order; there are thought to be 150,000 to 250,000 different species of moth , with thousands of species yet to be described...
s migrate over long distances to areas where they cannot settle for long periods of time. The term migratory butterfly or moth does not indicate a taxonomic clade within the Lepidoptera
Lepidoptera
Lepidoptera is a large order of insects that includes moths and butterflies . It is one of the most widespread and widely recognizable insect orders in the world, encompassing moths and the three superfamilies of butterflies, skipper butterflies, and moth-butterflies...
, but is a term that is used for all such species from the various included families that migrate.
Lepidoptera species migrate on all continents except Antarctica; they migrate from or within subtropical and tropical
Tropical climate
A tropical climate is a climate of the tropics. In the Köppen climate classification it is a non-arid climate in which all twelve months have mean temperatures above...
areas. The terms migratory butterfly and migratory moth are location-bound: they are only known as such in the areas where the species cannot establish themselves permanently.
By migrating, Lepidoptera species can avoid unfavorable circumstances, including weather, food shortage, or over-population. Like birds, there are Lepidoptera species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of which all individuals migrate, but there are also species of which only a subgroup of the individuals migrate.
The most famous Lepidopteran migration is that of the Monarch butterfly
Monarch butterfly
The Monarch butterfly is a milkweed butterfly , in the family Nymphalidae. It is perhaps the best known of all North American butterflies. Since the 19th century, it has been found in New Zealand, and in Australia since 1871 where it is called the Wanderer...
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
Danaus (genus)
Danaus, commonly called Tigers, Milkweeds, Monarchs, and Queens, is a genus of butterflies in the tiger butterfly tribe. They are found worldwide, including North America, South America, Africa, Asia, Indonesia and Australia...
in South India
South India
South India is the area encompassing India's states of Andhra Pradesh, Karnataka, Kerala and Tamil Nadu as well as the union territories of Lakshadweep and Pondicherry, occupying 19.31% of India's area...
are also prominent migrators, between Eastern Ghats
Eastern Ghats
The Eastern Ghats or Eastern Ghauts are a discontinuous range of mountains along India's eastern coast. The Eastern Ghats run from West Bengal state in the north, through Orissa and Andhra Pradesh to Tamil Nadu in the south passing some parts of Karnataka. They are eroded and cut through by the...
and Western Ghats
Western Ghats
The Western Ghats, Western Ghauts or the Sahyādri is a mountain range along the western side of India. It runs north to south along the western edge of the Deccan Plateau, and separates the plateau from a narrow coastal plain along the Arabian Sea. The Western Ghats block rainfall to the Deccan...
. Three species will be involved in this, namely Tirumala septentrionis
Tirumala septentrionis
The Dark Blue Tiger is a Danaid butterfly found in South and Southeast Asia.-Description:Closely resembles Tirumala limniace, Cramer, but is always sufficiently distinct to be easily recognized, even on the wing. From T...
, Euploea core
Euploea core
The Common Crow is a common butterfly found in South Asia. In India it is also sometimes referred to as the Common Indian Crow, and in Australia as the Australian Crow. It belongs to the Crows and Tigers subfamily of the Nymphalidae .The Common Crow is the most common representative of its genus...
, and Euploea sylvester
Euploea sylvester
The Double-branded Crow , also known as the Two-brand Crow in Australia, is a butterfly found in South Asia, Southeast Asia and parts of Australia that belongs to the Crows and Tigers, that is, the Danaid group of the Brush-footed butterflies family.Several races of the butterfly are recognized...
. Sometimes they are joined by Lemon Pansy (Junonia lemonias
Junonia lemonias
Junonia lemonias, also known as the Lemon Pansy, is a common nymphalid butterfly found in South Asia. It is found in gardens, fallow land, and open wooded areas.-Description:...
), Common Emigrant (Catopsilia pomona
Catopsilia pomona
The Common Emigrant or Lemon Emigrant is a medium sized pierid butterfly found in Asia and parts of Australia. The species gets its name from its habit of migration. Some early authors considered them as two distinct species Catopsilia crocale and Catopsilia pomona.-Description:The species has...
), Tawny coster (Acraea terpsicore
Acraea terpsicore
The Tawny Coster is a small leathery winged butterfly which is common in grassland and scrub habitats. It belongs to the Nymphalidae or brush-footed butterfly family. It has a weak fluttery flight. It is avoided by most insect predators...
) and Blue Tiger (Tirumala limniace
Tirumala limniace
The Blue Tiger is a butterfly found in India that belongs to the Crows and Tigers, that is, the Danaid group of the Brush-footed butterflies family. This butterfly shows gregarious migratory behaviour in southern India.-Description:...
).
Butterfly migration happens regularly in the foot hills of Himalayas. Due to lack of continuous study in this area, we don't have substantial information.
Definition
Migration in Lepidoptera refers to the act of moving from one place to another in a manner that is seasonally determined and predictable. There is no unambiguous definition of migratory butterfly or migratory moth, and this also applies to proposals to divide them into classes. Migration takes place so that organisms can avoid unfavourable environmental conditions that limit breeding.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
Ascia monuste
The Great Southern White is a species of butterfly of the Pieridae family in which the sexes differ in that the female can be either light or dark colored. It is found from the Atlantic and Gulf coasts of the United States, south through tropical America to Argentina...
, 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
Hibernation
Hibernation is a state of inactivity and metabolic depression in animals, characterized by lower body temperature, slower breathing, and lower metabolic rate. Hibernating animals conserve food, especially during winter when food supplies are limited, tapping energy reserves, body fat, at a slow rate...
or aestivation where they undergo diapause
Diapause
Diapause is the delay in development in response to regularly and recurring periods of adverse environmental conditions. It is considered to be a physiological state of dormancy with very specific initiating and inhibiting conditions...
and the same generation survives to return. The classic example is that of the nymphalid Monarch butterfly (Danuas plexippus).
The term migration is sometimes also applied to species which move over a vast area on their own strength, but remain within their known habitat
Habitat
* Habitat , a place where a species lives and grows*Human habitat, a place where humans live, work or play** Space habitat, a space station intended as a permanent settlement...
, although these are mostly referred to as strays. A well-known example of this is the Large White
Large White
The Large White , also called Cabbage Butterfly, Cabbage White, or in India the Large Cabbage White, White cabbage butterfly is a butterfly in the family Pieridae.-Distribution:...
. This species moves in great numbers, but only to areas where they can remain permanently.
In practice, the terms stray and migratory butterfly or moth overlap; there are species that can survive in a certain area, but in too small numbers to maintain the species in that area permanently. On the other hand, there are species that form a population for more than two years, but are still considered strays. Only when a species has a permanent population in an area for ten years, it is referred to as native.
To add to the confusion, the term stray is also used for migratory species that are not recorded each year, but from time to time. Species that have been recorded very few times are referred to as vagrants
Vagrancy (biology)
Vagrancy is a phenomenon in biology whereby individual animals appear well outside their normal range; individual animals which exhibit vagrancy are known as vagrants. The term accidental is sometimes also used...
.
Adventive
Species that are recorded in unexpected areas (adventive speciesAdventive species
An Adventive species is one that has arrived in the geographical area specified from somewhere else by any means , but is not self-sustaining and whose numbers are only increased through non-reproductive means, unlike a naturalised species.-See also:*Naturalisation *Introduced species*Invasive...
) 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
Galleria mellonella
The Greater Wax Moth or Honeycomb Moth is a moth of the family Pyralidae. It is the only member of the genus Galleria. It is found in most of the world, including Europe and adjacent Eurasia , and as an introduced species e.g...
, 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
Chrysodeixis chalcites
The Tomato Looper is a moth of the family Noctuidae. It is endemic to southern Europe, the Levant and tropical Africa, but can be found in great parts of Europe because it is a migratory species....
and Helicoverpa armigera
Helicoverpa armigera
The cotton bollworm, corn earworm or Old World bollworm, Helicoverpa armigera, is a moth, the larvae of which feed on a wide range of plants, including many important cultivated crops. It is a major pest in cotton and one of the most polyphagous and cosmopolitan pest species...
would be able to reach Western Europe on their own, but are also common in greenhouse
Greenhouse
A greenhouse is a building in which plants are grown. These structures range in size from small sheds to very large buildings...
s.
Seasonal migration
Season
A season is a division of the year, marked by changes in weather, ecology, and hours of daylight.Seasons result from the yearly revolution of the Earth around the Sun and the tilt of the Earth's axis relative to the plane of revolution...
al. With species of which all individuals migrate, the population
Population
A population is all the organisms that both belong to the same group or species and live in the same geographical area. The area that is used to define a sexual population is such that inter-breeding is possible between any pair within the area and more probable than cross-breeding with individuals...
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
Habitat
* Habitat , a place where a species lives and grows*Human habitat, a place where humans live, work or play** Space habitat, a space station intended as a permanent settlement...
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.
Difference with bird migration
An important difference with bird migrationBird migration
Bird migration is the regular seasonal journey undertaken by many species of birds. Bird movements include those made in response to changes in food availability, habitat or weather. Sometimes, journeys are not termed "true migration" because they are irregular or in only one direction...
is that an individual butterfly or moth usually migrates in one direction, while birds migrate back and forth multiple times within their lifespan. This is due to the short lifespan as an imago
Imago
In biology, the imago is the last stage of development of an insect, after the last ecdysis of an incomplete metamorphosis, or after emergence from the pupa where the metamorphosis is complete...
. Species that migrate back and forth, usually do so in different generations. There are however, some exceptions:
- The famous migration of the Monarch butterflyMonarch butterflyThe Monarch butterfly is a milkweed butterfly , in the family Nymphalidae. It is perhaps the best known of all North American butterflies. Since the 19th century, it has been found in New Zealand, and in Australia since 1871 where it is called the Wanderer...
in North America. This species migrates back and forth in one generation, though it completes only part of the journey in both directions in that generation. No individual completes the entire journey which is spread over a number of generations. The imagoImagoIn biology, the imago is the last stage of development of an insect, after the last ecdysis of an incomplete metamorphosis, or after emergence from the pupa where the metamorphosis is complete...
of the last summer generation is born in North America, migrates to Mexico, FloridaFloridaFlorida is a state in the southeastern United States, located on the nation's Atlantic and Gulf coasts. It is bordered to the west by the Gulf of Mexico, to the north by Alabama and Georgia and to the east by the Atlantic Ocean. With a population of 18,801,310 as measured by the 2010 census, it...
, or CaliforniaCaliforniaCalifornia is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
and stays there for the winter. After the winter it migrates back to the north to reproduce. In a couple of generations, the monarch migrates north to Canada. - The migration of Agrotis infusa in Australia. This species migrates from south-eastern Australia to the Australian AlpsAustralian AlpsThe Australian Alps are the highest mountain ranges of mainland Australia. They are located in southeastern Australia and straddle the Australian Capital Territory, south-eastern New South Wales and eastern Victoria...
in the summer to avoid the heat. After the summer it returns to reproduce.
Flight behaviour
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. The migration is carried out by relying on heavy winds; a persistent wind speed of 10 metres per second being able to provide a displacement of 300 to 400 kilometers in a single day. For example, the Painted Lady (Vanessa cardui
Vanessa cardui
Vanessa cardui is a well-known colourful butterfly, known as the Painted Lady, or in North America as the Cosmopolitan. This butterfly has a strange pattern of flying in a sort of screw shape.-Distribution:...
) migrates from Africa to Spain aided by head winds.
That the migratory species are good flyers, is not the same as saying they are robust flyers. The small Diamondback moth
Diamondback moth
The diamondback moth , sometimes called cabbage moth, is a European moth believed to originate in the Mediterranean region that has since spread worldwide. The moth has a short life cycle , is highly fecund and capable of migrating long distances...
is also a migratory species that migrates 3,000 kilometers and can be found up to altitudes of 100 meters or more.
Navigation
To be able to migrate over long distances, species must be able to navigate. There are several ways they do this.Landscape: Lepidoptera use coastal lines, mountains, but also man-made roads to orient themselves. Above sea it has been observed that the flight direction is much more accurate if the landscape on the coast is still visible.
Celestial navigation: Butterflies are known to be capable of navigation with the help of the sun. They can also navigate by using polarized light. The polarization of the sun's light changes with the angle of the rays, hence they can also navigate with cloudy weather. There are indications that they can even make corrections depending on the time on a day. Diamondback moths are known to fly in a straight trajectory which is not dependent on the angle of the sun's rays. 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. The conclusion was that some species did, and others did not. Research on monarchs demonstrates that with removal of antennae, the location of the circadian clock, individuals do not localize in any one direction during flight as they do with antennae intact. Night flyers cannot use sun light for navigation. Most of these species rely on the moon and stars instead.
Earth’s magnetic field: A number of moths use the Earth's magnetic field
Earth's magnetic field
Earth's magnetic field is the magnetic field that extends from the Earth's inner core to where it meets the solar wind, a stream of energetic particles emanating from the Sun...
to navigate, as a study of the stray Heart and Dart
Heart and Dart
The Heart and Dart is a moth of the family Noctuidae. A familiar moth to many, it is considered one of the most common of the European region....
suggests. Another study, this time of the migratory behaviour of the Silver Y
Silver Y
The Silver Y is a migratory moth of the family Noctuidae which is named for the silvery Y-shaped mark on each of its forewings.-Description:...
, showed that this species, even at high altitudes, can correct its course with changing winds, and prefers flying with favourable winds, which suggests a great sense of direction. Aphrissa statira
Aphrissa statira
The Statira Sulphur, Aphrissa statira, is a species of lepidoptera in the family Pieridae.-Description:Aphrissa statira have a wingspan of about to ....
in Panama
Panama
Panama , officially the Republic of Panama , is the southernmost country of Central America. Situated on the isthmus connecting North and South America, it is bordered by Costa Rica to the northwest, Colombia to the southeast, the Caribbean Sea to the north and the Pacific Ocean to the south. The...
loses its navigational capacity when exposed to a magnetic field, suggesting it uses the Earth’s magnetic field.
Areas where migratory butterflies and moths can be found
Migratory Lepidoptera can be found on all continentContinent
A continent is one of several very large landmasses on Earth. They are generally identified by convention rather than any strict criteria, with seven regions commonly regarded as continents—they are : Asia, Africa, North America, South America, Antarctica, Europe, and Australia.Plate tectonics is...
s, migrating within or from the Tropics
Tropics
The tropics is a region of the Earth surrounding the Equator. It is limited in latitude by the Tropic of Cancer in the northern hemisphere at approximately N and the Tropic of Capricorn in the southern hemisphere at S; these latitudes correspond to the axial tilt of the Earth...
and Subtropics
Subtropics
The subtropics are the geographical and climatical zone of the Earth immediately north and south of the tropical zone, which is bounded by the Tropic of Cancer and the Tropic of Capricorn, at latitudes 23.5°N and 23.5°S...
. North, they can be found up to Spitsbergen
Spitsbergen
Spitsbergen is the largest and only permanently populated island of the Svalbard archipelago in Norway. Constituting the western-most bulk of the archipelago, it borders the Arctic Ocean, the Norwegian Sea and the Greenland Sea...
, above the Arctic Circle
Arctic Circle
The Arctic Circle is one of the five major circles of latitude that mark maps of the Earth. For Epoch 2011, it is the parallel of latitude that runs north of the Equator....
. Some migratory Lepidoptera have spread over most of the world. Some of these are pest insects, such as the diamondback moth
Diamondback moth
The diamondback moth , sometimes called cabbage moth, is a European moth believed to originate in the Mediterranean region that has since spread worldwide. The moth has a short life cycle , is highly fecund and capable of migrating long distances...
, Helicoverpa armigera
Helicoverpa armigera
The cotton bollworm, corn earworm or Old World bollworm, Helicoverpa armigera, is a moth, the larvae of which feed on a wide range of plants, including many important cultivated crops. It is a major pest in cotton and one of the most polyphagous and cosmopolitan pest species...
, and Trichoplusia ni.
Examples of migratory Lepidoptera
Some examples of Migratory Lepidoptera are:- In the Indian subcontinent, migrating Lepidoptera are common just before the monsoonMonsoonMonsoon is traditionally defined as a seasonal reversing wind accompanied by corresponding changes in precipitation, but is now used to describe seasonal changes in atmospheric circulation and precipitation associated with the asymmetric heating of land and sea...
season. Over 250 species are known to migrate during this period. - On MadagascarMadagascarThe Republic of Madagascar is an island country located in the Indian Ocean off the southeastern coast of Africa...
, Chrysiridia rhipheus migrates between populations of four plant species from the OmphaleaOmphaleaOmphalea is a plant genus of the family Euphorbiaceae and the only genus of its tribe . It comprises 17 species, all of which are tropical shrubs, trees or lianas. 12 of them are native to the Americas, 4 are endemic to Madagascar and 1 to Africa...
genus, the host plant of this species. The three western Omphalea species live in dry coniferous forests, the eastern species is found in the rainforestRainforestRainforests are forests characterized by high rainfall, with definitions based on a minimum normal annual rainfall of 1750-2000 mm...
and is the only species that is green year round. - Rhodometra sacrariaRhodometra sacrariaThe Vestal is a moth of the family Geometridae. It is found throughout Europe, Africa and large parts of Asia.The wingspan is 22-28 mm. The length of the forewings is 12-14 mm...
is normally found in Africa, large parts of Asia and Southern Europe. At times, it migrates north and can reach central and northern Europe. - Vanessa carduiVanessa carduiVanessa cardui is a well-known colourful butterfly, known as the Painted Lady, or in North America as the Cosmopolitan. This butterfly has a strange pattern of flying in a sort of screw shape.-Distribution:...
is found all over the world, except South America, on altitudes of up to 3,000 meters above sea level. Its home, however, are subtropical steppeSteppeIn physical geography, steppe is an ecoregion, in the montane grasslands and shrublands and temperate grasslands, savannas, and shrublands biomes, characterized by grassland plains without trees apart from those near rivers and lakes...
areas. - Several South and Central American species of UraniidaeUraniidaeThe Uraniidae are a family of moths containing four subfamilies, ninety genera, and roughly seven-hundred species. The family is distributed throughout the tropics of Americas, Africa and Indo-Australia. Some of the tropical species are known for their bright, butterfly-like colors and are called...
display a great peak in migratory behavior in certain years. In the years with a great number of migrating individuals, there are “population explosions”. Individuals migrate to the south and east. There is no real re-migration to speak off. These moths feed on OmphaleaOmphaleaOmphalea is a plant genus of the family Euphorbiaceae and the only genus of its tribe . It comprises 17 species, all of which are tropical shrubs, trees or lianas. 12 of them are native to the Americas, 4 are endemic to Madagascar and 1 to Africa...
species. These can be found in scattered populations all across South and Central America, but only part of the areas where they are found are a permanent habitat for these moths. Research suggests that the cause of the migration peak is an increase in toxicityToxicityToxicity is the degree to which a substance can damage a living or non-living organisms. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a substructure of the organism, such as a cell or an organ , such as the liver...
when much of a single plant is eaten and decreasing toxicity when only small amounts of a certain plant are eaten. - The migration of Euploea coreEuploea coreThe Common Crow is a common butterfly found in South Asia. In India it is also sometimes referred to as the Common Indian Crow, and in Australia as the Australian Crow. It belongs to the Crows and Tigers subfamily of the Nymphalidae .The Common Crow is the most common representative of its genus...
, Euploea sylvesterEuploea sylvesterThe Double-branded Crow , also known as the Two-brand Crow in Australia, is a butterfly found in South Asia, Southeast Asia and parts of Australia that belongs to the Crows and Tigers, that is, the Danaid group of the Brush-footed butterflies family.Several races of the butterfly are recognized...
and Tirumala septentrionisTirumala septentrionisThe Dark Blue Tiger is a Danaid butterfly found in South and Southeast Asia.-Description:Closely resembles Tirumala limniace, Cramer, but is always sufficiently distinct to be easily recognized, even on the wing. From T...
between Western Ghats and Eastern Ghats in India covering up to 350 to 400 km. This migration happens twice a year. The most probable reasons seem to be the Monsoons, lack of diapause and host plants, nectar and alkaloidal resource availability.
Example species: Macroglossum stellatarum
Macroglossum stellatarum is a moth that is recorded in the subtropical part of the Palearctic ecozone year round. In summer, the species migrate north up to Scandinavia and IcelandIceland
Iceland , described as the Republic of Iceland, is a Nordic and European island country in the North Atlantic Ocean, on the Mid-Atlantic Ridge. Iceland also refers to the main island of the country, which contains almost all the population and almost all the land area. The country has a population...
. In winter it migrates further south, deeper into Africa and to the Indian subcontinent.
In the Netherlands and Belgium, there are 100 to 200 records per year in an average year. In warm summers however, like the years 2005 and 2006, several thousand are recorded. In mild winters, small numbers can survive this far north, but these numbers are insufficient to call it a real population.
Causes
Usually, butterflies and moths migrate to escape from potentially harmful circumstances. Examples of this are a shortage of proper food plants, an unfavorable climate, like cold or extreme rain or overpopulation.Migration and evolution
Natural selection
Natural selection is the nonrandom process by which biologic traits become either more or less common in a population as a function of differential reproduction of their bearers. It is a key mechanism of evolution....
. There are a number of advantages and disadvantages to migration.
Positive effects for the species
There are positive effects for all Lepidoptera species when migrating over even small distances. It ensures sufficient genetic mixing, which in turn ensures there is no inbreedingInbreeding
Inbreeding is the reproduction from the mating of two genetically related parents. Inbreeding results in increased homozygosity, which can increase the chances of offspring being affected by recessive or deleterious traits. This generally leads to a decreased fitness of a population, which is...
. When the displacement takes place over longer distances, this can also lead to the discovery of new suitable habitats, making the species less vulnerable.
Furthermore, displacement over long distances makes it possible to escape from unfavorable circumstances like drought or cold. This makes migration a suitable alternative for diapause
Diapause
Diapause is the delay in development in response to regularly and recurring periods of adverse environmental conditions. It is considered to be a physiological state of dormancy with very specific initiating and inhibiting conditions...
. After the negative circumstances have passed, members of the species return to their place of origin.
There are also migratory species that move over long distances, without any recorded re-migration, like several "Sphingidae
Sphingidae
Sphingidae is a family of moths , commonly known as hawk moths, sphinx moths and hornworms, that includes about 1,200 species . It is best represented in the tropics but there are species in every region . They are moderate to large in size and are distinguished among moths for their rapid,...
" species. Some individuals possibly return to their original habitat, but these are only small numbers. The advantages of migration are not all that clear for these species. Researchers think the causes are the food plants of these species, which are mainly herbaceous plants. These plants are more vulnerable for external influences, like drought, in comparison with shrubs or trees. To tackle this problem, a possible solution is migration, which has the additional benefit for the species also escaping from these negative external influences. The fact that many of the migrating individuals find themselves in areas where they cannot survive permanently is apparently of less significance. Furthermore, even a small number of re-migrating individuals can ensure the re-emerging of a population in their original habitat.
Negative effects for the species
Migration has some negative effects on a species. The migration itself costs a lot of energy and is not without risk. During the trip, many individuals die and not all survivors find a suitable habitat. On the outskirts of suitable habitat, fertility can decrease. Acherontia atroposAcherontia atropos
Acherontia atropos is the most widely-known of the three species of Death's-head Hawk moth. Acherontia species are notorious mainly for a vaguely skull-shaped pattern on the thorax.-Appearance:...
females that are born in temperate areas are significantly less fertile, or not fertile at all.
Reproduction in favorable areas must thus be very high, to shift the balance in favor of migration.
Recording
Butterflies (and to a lesser extent moths) migrating in large numbers are a noteworthy sight, which is easily to observe and track. There are several historic records about migrating butterflies. There are records dating back to 1100 about migrating butterflies (probably a Pieris species) from BavariaBavaria
Bavaria, formally the Free State of Bavaria is a state of Germany, located in the southeast of Germany. With an area of , it is the largest state by area, forming almost 20% of the total land area of Germany...
to the Duchy of Saxony
Duchy of Saxony
The medieval Duchy of Saxony was a late Early Middle Ages "Carolingian stem duchy" covering the greater part of Northern Germany. It covered the area of the modern German states of Bremen, Hamburg, Lower Saxony, North Rhine-Westphalia, and Saxony-Anhalt and most of Schleswig-Holstein...
and from 1248 about the migration of yellow butterflies in Japan.
When flying at high altitudes, spotting migrating butterflies or moths can be hard. Low flying species are easily spotted or caught using a light trap. When individuals fly too high for these methods, air balloons equipped with nets are used at times. Alternatively, radar
Radar
Radar is an object-detection system which uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits pulses of radio...
is used to monitor migration.
Another registration technique, is marking the wings with tiny sticker
Sticker
A sticker is a type of a piece of paper or plastic, adhesive, sticky on one side, and usually with a design on the other. They can be used for decoration, depending on the situation. They can come in many different shapes, sizes and colours and are put on things such as lunchboxes, in children's...
s, a technique comparable with Bird ringing
Bird ringing
Bird ringing or bird banding is a technique used in the study of wild birds, by attaching a small, individually numbered, metal or plastic tag to their legs or wings, so that various aspects of the bird's life can be studied by the ability to re-find the same individual later...
. This technique has not proven to be very successful though. Advances in technology might make it possible to equip individuals with micro transmitters in the future.
Registration
Both The Netherlands and Belgium have a register of recorded migratory species. In the Netherlands, registration (Trekvlinderregistratie Nederland) started in 1940 and is the world's oldest project in this field., in Belgium, the registration is called Belgisch Trekvlinder Onderzoek.Migration and climate change
It seems that global warmingGlobal warming
Global warming refers to the rising average temperature of Earth's atmosphere and oceans and its projected continuation. In the last 100 years, Earth's average surface temperature increased by about with about two thirds of the increase occurring over just the last three decades...
has caused an increase of migratory butterflies and moths that reach north-western countries like the Netherlands, Belgium and the United Kingdom. Research in the United Kingdom confirms that an increasing number of migrants reach the country. Because one would expect that migratory species can adapt to new circumstances quite well, the researches warn for new species that can have a negative impact on native species and possible damage to both health (species like the Oak Processionary
Oak Processionary
The Oak Processionary is a moth whose caterpillars are pests in oak forests and pose a health hazard because of their poisonous setae , which may cause skin irritation and asthma.- Distribution :...
) and agriculture.