Migratory butterflies

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Monarch butterfly

Migratory butterflies are butterflies that migrate over long distances from reproductive areas . This behavior is known from over 200 mostly tropical species. When migration is an outgoing from the animal, sustained motion, in a more or less fixed direction, which is controlled by it, respectively. The migratory moths can be recognized by their determined flight. There are migratory movements of individual animals at intervals of a few minutes or seconds that fly quickly and at approximately the same height in the same direction, or migratory movements of flocks of animals. It is also noticeable that obstacles are flown over or around and the flight then continues in the original direction.

Causes of wandering

In the temperate zones there are distinct seasons with strongly fluctuating temperatures between summer and winter. In the tropical and subtropical zones there are sometimes alternating rainy and dry seasons. As a result, living conditions are very different in many regions of the world over the course of the year and various adaptation strategies have developed in insects in the course of evolution . These strategies fall into two groups. The stayers survive the unfavorable time with various forms of dormancy in which the metabolism is greatly reduced. The hikers , on the other hand, leave the area and escape the unfavorable living conditions.

The reason for the migration has not been sufficiently clarified in all cases, since most of the animals do not survive the winter of some species that migrate to Central Europe and do not fly back in time. A strategy for accidental area expansion is obvious, at least the cause is the withering of nectar and food plants in the area of ​​origin during the summer or the dry season. It is also possible that some migratory butterflies still follow an atavism, i.e. are influenced by other climatic conditions.

In some species, the migratory instinct only begins when there is a certain population density, similar to what is known from migratory locusts .

Known species

In Central Europe , the admiral ( Vanessa atalanta ) and the painted lady ( Vanessa cardui ) fly in from the Mediterranean area every year via the Alps and the Burgundian Gate , sometimes as far as Scandinavia . Some species such as the line hawk ( Hyles livornica ) even fly in from the tropics of Africa via the Sahara to Central Europe. Other known migratory butterflies in Europe are the postillon ( Colias crocea ) or the skull hawk ( Acherontia atropos ). Outside of Europe, the American monarch butterfly ( Danaus plexippus ) is particularly known for its mass migrations in North America .

The painted lady migrates not only in North Africa and Europe, but also in many other parts of the world. In California, for example, a migration was observed in a total of 36 hours of daylight, which was estimated to be 3 billion animals. In Sri Lanka , 26,000 animals per minute were counted for three species of white whites migrating together.

Sometimes individual animals cover up to two thousand kilometers, such as the pigeon tail ( Macroglossum stellatarum ) or the painted lady. The monarch butterfly covers up to four thousand kilometers on its migrations, with the migration to the north taking place over several generations, the return migration in autumn over the entire route is only managed by the last generation of the year.

Fastest fly the moth (Sphingidae), and in particular of the tobacco hornworm ( Agrius convolvuli can reach a speed of up to 100 km /) h, its average speed but still h still 50 km /. The pigeon tail with an average speed of around 40 km / h is also one of the fastest among them.

orientation

The migratory butterflies can orientate themselves partly on landmarks, the sun and the earth's magnetic field. This enables them to compensate for deviations from the flight route caused by wind drift and to fly into the same areas regularly. On long-haul flights, they use the sun and probably the Earth's magnetic field, while on short-haul flights, landmarks serve as orientation.

Landmarks

Coastlines, mountains and mountain ranges and roads have been identified as landmarks that are used for orientation. When flying over bodies of water with still visible landmarks, the deviation from the planned course is very small; if these are missing, for example over the sea, significant deviations from the course can occur.

Solar compass

The moths are able to compensate for the position of the sun (azimuth), which depends on the season and the latitude, and to keep their course during the day with the help of a solar compass. However, this is significantly less accurate than when using landmarks for orientation. How the compensation works has not been clarified, as previous studies have not provided any clear results. A solar compass has been proven for the monarch, Aphrissa statira and Phoebis argante (both whites). The moths can see polarized ultraviolet light . Even when the sky is overcast, the polarization axis can be perceived and enables quite precise navigation.

Earth's magnetic field

For a long time it has been assumed that individual species can also use the earth's magnetic field for orientation. Monarch butterflies have magnetite in their heads and can orient themselves using the earth's magnetic field. Strong magnetic fields disturb their orientation just as lastingly as with Aphrissa statira , where it was proven in Panama .

Classification of hiking behavior

Four groups are distinguished within the migrant butterflies. A fundamental distinction is made between the consecutive species that only migrate when the environmental conditions change and the prospective species that migrate before a change occurs.

Some species are assigned different types depending on the habitat and population that influence behavior. An example of this is the American monarch butterfly that lives in the western United States. In summer they fly north into the valleys of the Rocky Mountains and return to California in winter (first-order seasonal hikers). In contrast, the central population, which lives in the mid-west and east of the United States to southern Canada in summer, winters in the mountains of Mexico and pauses for development, as winters in central Mexico are cooler than in the coastal areas (seasonal hikers 2nd order ). Parts of this population overwinter in Florida and some of them reproduce without a break in development over the mild winter. These are then again classified as first-order seasonal hikers. There are populations of the Gammaeule ( Autographa gamma ) that immigrate from the Mediterranean to Central Europe and are counted as 1st order seasonal hikers and indigenous populations in Central Europe that are counted as 2nd order seasonal hikers.

There is still a great need for research for numerous species in Europe, as it is not clear to what extent a return migration takes place and thus an allocation to this group is correct. For a long time there were records mainly from the southern part of England, Germany, Austria and Switzerland, which only cover areas between the 50th and 55th parallel. In North America, on the other hand, the area between the 35th and 45th parallel has been well researched and autumn (back) migrations are much more noticeable here than spring migrations.

Prospective migrants

Seasonal hikers 1st order (eumigrants)

Painted Lady ( Vanessa cardui )

The first-order seasonal hikers leave their current breeding area at certain times of the year and fly to another, fixed breeding area. There they lay eggs from which the next generation emerges. Either the animals of the first generation migrate back to the original areas or one of their successor generations. If the animals migrate so far beyond their territorial boundaries that their offspring can no longer return, one speaks of wandering guests.

The prospective migrants leave their breeding area almost completely closed and multiply in the target area. You will thus later escape the following unfavorable living conditions in the area of ​​origin. In no phase of development is there a rest, while the seasonal hikers of the 2nd order have a standstill in sexual maturation during their dormancy. For many species there is no strong re-migration. The causes have not been conclusively clarified, but it is assumed that the genetic intermingling of oppositely migrating individuals no longer triggers the return migration.

Sample types:

Seasonal hikers 2nd order (paramigrants)

Hibernating Monarch Butterflies ( Danaus plexippus ) gather in Santa Cruz, USA

The seasonal hikers of the 2nd order leave their breeding area at certain times of the year in order to overwinter or over summer in a dormancy, which often takes place as a diapause . After the resting phase, all animals return to their original areas. Only after their return do the animals reproduce. Before their return, the animals are still sterile.

Shortly after hatching, the hackberry butterfly leaves its hot breeding areas south of the Alps and retreats to the mountains to spend the summer. It only flies back to the original lowlands in autumn and forms the next generation.

Sample types:

  • American monarch butterfly ( Danaus plexippus ) (depending on population)
  • Hackberry butterfly ( Libythea celtis )
  • Russian bear or Spanish flag ( Euplagia quadripunctaria )
  • Gamma owl ( Autographa gamma ) (depending on population)

Consecutive migrants

Internal migrants (emigrants)

Line swarmers ( Hyles livornica )

The inland migrants often fly to other regions within their area of ​​distribution and often only cover short distances, similar to the line birds . A few tens to a few hundred kilometers are covered. The pigeon tail, for example, is an exception with migrations of up to 2000 kilometers. The animals do not return to their original areas, and the migration does not primarily serve to preserve the species. Sometimes this increases the species’s habitat for a period of time. In Europe, this includes various white flies (Pieridae) and the peacock butterfly ( Inachis io ).

The American cabbage white butterfly ( Ascia monuste ) lives all year round on the southern tip of Florida . Parts of this population migrate north along the east and west coasts in a four-month period when there is particularly high population pressure. This significantly increases the breeding area. The newly established populations usually collapse again after a few years in cold winters. The wandering movements are easy to distinguish from normal flying around. Migratory moths fly in streams up to 15 meters wide, rarely more than three to four meters above the ground. When there is wind, they fly on the leeward side of dunes , when there is no wind they cross the dunes. This means that your flights are largely independent of the wind.

Sample types:

Hunt group (dismigrants)

Sail butterfly ( Iphiclides podalirius )

All species whose migratory behavior has not yet been proven, but which are suspected to be migrating, are recorded in the collective group. Species that expand their range - the so-called area expanders - and species that tend to extreme population fluctuations and spontaneously and aimlessly leave their breeding area when there is high population pressure are also recorded here. In the last few decades , the map has expanded its distribution area in south-western and northern Europe. The sailing butterfly ( Iphiclides podalirius ) has expanded its range in Germany in recent years. There was growth in Saxony on the Elbe and in Niederlausitz .

Examples of suspected migratory species:

Examples of area expansions:

Observations

From a report on a mass occurrence of the wind swarm ( Herse convolvuli ) in 1719

Mass migrations of insects caught people's attention early on. One of the oldest traditions can be found in the book of Exodus ( Exodus 10 : 13-19  EU , around 1500 BC): “ God sent an east wind over the land all day and the following night; when morning came the wind sent the locusts. And the locusts fell on all the land of Egypt ... they covered the face of the earth ... and they left nothing green in the whole land, neither tree nor herb in the field. "The influence of the wind on the spread of the animals was also noticed:" God turned the wind and sent a strong westerly wind, which seized the locusts and threw them into the Red Sea. "

From the year 1100 there is a description of a butterfly migration, probably cabbage whites, from Saxony to Bavaria. More than 400 years later, the Chronicles of Calais in the Reigns of Henry VII and Henry VIII read: “ On July 9, 1508, in the 23rd year of Henry VII , on a Sunday, an immense flock of white butterflies flew off near Calais North to southeast. It was like a heavy snowstorm, so that at 4 o'clock in the afternoon you couldn't even see the city of Calais from St. Petars. “This was the Great Cabbage White, which even today migrates in the direction described in some years at this time of the year.

Old reports of migratory moths have come down not only from Europe, but also from Japan, for example from 1248, when two migrations of yellow moths were observed from the coast of Yuigahama into the interior of Kamakura within 14 days .

An often-cited recent observation (June 8 or 10, 1826) reports on the painted lady on Lake Neuchâtel ( Switzerland ): “The moths moved northwards in a narrow front of three to five meters for more than 2 hours. In 1879 the same species moved in previously unknown strength from North Africa across Europe to the north. ”Almost 100 reports of sightings from Spain, France, Italy, Germany, Switzerland, the Netherlands, Belgium and the British Isles have survived.

research

The migratory behavior of the American monarch in North America and the painted lady in Europe has been particularly well researched. In India , the migratory behavior of numerous butterflies is also scientifically investigated, many species not only roam the Indian subcontinent, but also cross the Himalayas .

In the middle of the 19th century, the Englishman Edward Newman published his shipping theory , in which he took the view that the mignonette, the oleander hawk and the wandering blue can fly across the English Channel to the British Isles. In 1842 Marcel de Serres reported on various butterflies and swarmers who flew into France over the Mediterranean. Both were not taken seriously by their specialist colleagues, even laughed at, since it was thought at the time that insects only lived a few days and, with the exception of locusts, could not cross the open sea. Interest in insect migrations only increased in the professional world at the beginning of the 20th century after a hobby entomologist reported on insect migrations and in particular on butterflies in the Entomologists Record , which was recognized worldwide. In 1930 The Migration of Butterflies by Carrington Bonsor Williams appeared, in which over 1000 messages from more than 200 species of butterflies were evaluated.

The German Research Center for Butterfly Migration eV (DFZS) was founded by Kurt Harz in 1964 to research the migratory behavior of insects in Europe . This established an observer network of professional and hobby entomologists in Central Europe and publishes its research results in the club's own magazine Atalanta , which appears at least once a year. By working with similar institutions in the Netherlands, Belgium, Great Britain, Denmark, Finland, Austria and Switzerland, and at times also in Yugoslavia, we have succeeded in drawing a picture of immigration flows. Little is known about the return migration.

The basic data comes from many helpers who report migrating moths. In the past, reports were made using special reporting cards; since 2003 there has been an internet portal in which observations can be entered.

There are several research institutions in North America that observe and study the migration of the monarch butterfly.

Track hikes

Recognizing migratory animals based on their flight behavior is the easiest way to track migrations, but it is difficult here to determine where the migration begins and ends. An attempt is made to find out more about flight behavior by marking individual animals with small stickers in the field or from breeding. This procedure is very complex and the success is low, since only very few butterflies are found and reported. Frederick Urquhart and his helpers tagged hundreds of thousands of monarch butterflies in order to research the migration and find the wintering places in Mexico. Larger swarms can also be tracked with small aircraft, while very large swarms can even be tracked with radar stations. Radio stations that can be attached to animals have reached 0.2 grams and are likely to become even lighter. With a battery life of around three weeks, it will probably also be able to track butterflies in the future, whose flights are still completely unknown.

biology

In addition to the migratory movement, the biology of animals is researched. The degree of maturity of the sexual organs ( gonads ) is examined on captured animals in order to gain knowledge about dormancy.

It was mainly US research groups that investigated how the moths orient themselves and what causes them to migrate. It was investigated how animals in halls follow artificial light sources and how strong magnetic exposure affects further flight behavior outdoors.

Individual evidence

  1. ↑ Thomas C. Emmel: Wonderful and mysterious world of butterflies . Bertelsmann Lexikon-Verlag, Gütersloh and Berlin 1976, ISBN 3-570-00893-2 , p. 60 .
  2. ↑ Robert B. Srygley, Evandro G. Oliveira: Sun compass and wind drift compensation in migrating butterflies . In: Journal of Navigation . tape 54 . Cambridge University Press, 2001, ISSN  0373-4633 , pp. 405–417 ( bio-nica.info [PDF; accessed February 3, 2008]).
  3. ↑ Steven M. Reppert, Haisun Zhu, and Richard H. White: Polarized Light Helps Monarch Butterflies Navigate . In: Current Biology . No. 14 . Cell Press, January 20, 2004, ISSN  0960-9822 , p. 155-158 .
  4. ↑ Jason A. Etheredge, Sandra M. Perez, Orley R. Taylor & Rudolf Jander: Monarch butterflies (Danaus plexippus L.) use a magnetic compass for navigation . In: Proceedings of the National Academy of Sciences (PNAS) . tape 96 , no. 24 , 1999, pp. 13845–13846 ( pnas.org [PDF; 60 kB ; accessed on September 27, 2008] This article has been withdrawn).
  5. ^ Sandra M. Perez, Orley R. Taylor & Rudolf Jander: The Effect of a Strong Magnetic Field on Monarch Butterfly (Danaus plexippus) Migratory Behavior . In: Natural Sciences . tape 86 . Springer, 1999, p. 140-143 .
  6. ↑ Robert B. Srygley, Evandro G. Oliveira, Andre J. Riveros: Experimental evidence for a magnetic sense in Neotropical migrating butterflies (Lepidoptera: Pieridae) . In: Animal Behavior (The British Journal of Animal Behavior) . tape 71 . Elsevier, January 1, 2006, ISSN  0003-3472 , p. 183–191 ( ( Page no longer available , search in web archives: users.ox.ac.uk ) [accessed February 3, 2008]).@1@ 2Template: dead link / users.ox.ac.uk
  7. ^ A b Malcolm J. Scoble: The Lepidoptera: Form, Function and Diversity . Oxford University Press, Oxford 1995, ISBN 0-19-854952-0 , pp. 68 ff . (English).
  8. ↑ Jürgen Hensle: Butterfly Monitoring. (No longer available online.) In: Science 4 you. Formerly in the original ; Retrieved February 1, 2008 .  ( Page no longer available , search in web archives )  Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice.@1@ 2Template: Dead Link / www.science4you.org  
  9. ↑ Jürgen Hensle: Papiliondae, Pieridae, Nymphalidae and Lycaenidae 2006 . In: Society for the Promotion of Research on Insect Migration in Germany eV, Munich (Ed.): Atalanta . No. 38 . DFZS, August 2007, ISSN  0171-0079 , p. 16 .
  10. ↑ Mani, MS: Butterflies of the Himalaya . In: Series Entomologica . Oxford & IBH Publishing Co., New Delhi 1986, ISBN 90-6193-545-8 , pp. 16 .
  11. ↑ B. Naef-Daenzer, D. Früh, M. Stalder, P. Wetli & E. Weise: Miniaturization (0.2 g) and evaluation of attachment techniques of telemetry transmitters . In: Journal of Experimental Biology . tape 208 , 2005, pp. 4063-4068 , doi : 10.1242 / jeb.01870 .

literature

German

  • Williams, Carrington Bonsor: The Migratory Flights of Insects. Introduction to the problem of the migration behavior of insects with special consideration of butterflies . Paul Parey, Hamburg, Berlin 1961.
  • Ulf Eitschberger, Rolf Reinhardt, Hartmut Steiniger: Migratory butterflies in Europe . In: Society for the Promotion of Research on Insect Migration in Germany eV, Munich (Ed.): Atalanta . No. 22 . DFZS, April 1991, ISSN  0171-0079 , p. 4-17 .

English

  • Williams, Carrington Bonsor: The Migration of Butterflies . Oliver & Boyd, Edinburgh 1930.
  • Williams, Carrington Bonsor: Insect Migration . In: The New Naturalist . tape 36 . Collins, London 1958.
  • Urquhart, Frederick Albert: The Monarch Butterfly: International Traveler . Nelson Hall Publishers, 1987, ISBN 978-0-8304-1039-2 .

Web links