Insect migration is the seasonal movement of insects, particularly those by species of dragonflies, beetles, butterflies and moths. The distance can vary with species and in most cases, these movements involve large numbers of individuals. In some cases, the individuals that migrate in one direction may not return and the next generation may instead migrate in the opposite direction. This is a significant difference from bird migration.
All insects move to some extent. The range of movement can vary from within a few centimeters for some sucking insects and wingless aphids to thousands of kilometers in the case of other insects such as locusts, butterflies and dragonflies. The definition of migration is therefore particularly difficult in the context of insects. A behavior-oriented definition proposed is
Migratory behavior is persistent and straightened-out movement affected by the animal's own locomotory exertions or by its active embarkation on a vehicle. It depends upon some temporary inhibition of station-keeping responses but promotes their eventual disinhibition and recurrence.
— Kennedy, 1985 [1]
This definition disqualifies movements made in the search of resources and which are terminated upon finding the resource. Migration involves longer distance movement and these movements are not affected by the availability of the resource items. All cases of long-distance insect migration concern winged insects. [2]
Many migrating butterflies fly at low altitudes. The airspeeds in this region are typically lower than the flight speed of the insect, allowing them to travel against the wind if need be. These 'boundary-layer' migrants include the larger day-flying insects, and their low-altitude flight is easier to observe than that of most high-altitude windborne migrants. [3] Some species of butterfly (such as Vanessa atalanta and Danaus plexippus ) are known to migrate using high-altitude, high-speed winds during their yearly migrations. [4]
Many migratory species tend to have polymorphic forms, a migratory one, and a resident phase. The migratory phases are marked by their well-developed and long wings. Such polymorphism is well known in aphids and grasshoppers. In the migratory locusts, there are distinct long and short-winged forms. [5]
The energetic cost of migration has been studied in the context of life-history strategies. It has been suggested that adaptations for migration would be more valuable for insects that live in habitats where resource availability changes seasonally. [6] Others have suggested that species living in isolated islands of suitable habitats are more likely to evolve migratory strategies. The role of migration in gene flow has also been studied in many species. [7] Parasite loads affect migration. Severely infected individuals are weak and have shortened lifespans. [8] Infection creates an effect known as culling whereby migrating animals are less likely to complete the migration. This results in populations with lower parasite loads. [9]
Migration is usually marked by well defined destinations which need navigation and orientation. A flying insect needs to make corrections for crosswinds. [10] It has been demonstrated that many migrating insects sense wind speed and direction and make suitable corrections. [11] Day-flying insects primarily make use of the sun for orientation, however, this requires that they compensate for the movement of the sun. Endogenous time-compensation mechanisms have been proposed and tested by releasing migrating butterflies that have been captured and kept in darkness to shift their internal clocks and observing changes in the directions chosen by them. Some species appear to make corrections while it has not been demonstrated in others. [12]
Most insects are capable of sensing polarized light and they are able to use the polarization of the sky when the sun is occluded by clouds. [13] The orientation mechanisms of nocturnal moths and other insects that migrate have not been well studied, however magnetic cues have been suggested in short distance fliers. [14]
Recent studies suggest that migratory butterflies may be sensitive to the Earth's magnetic field on the basis of the presence of magnetite particles. [15] In an experiment on the monarch butterfly, it was shown that a magnet changed the direction of initial flight of migrating monarch butterflies. [16] However this result was not a strong demonstration since the directions of the experimental butterflies and the controls did not differ significantly in the direction of flight. [10]
Migration of butterflies and moths is particularly well known.
The Bogong moth is a native insect of Australia that is known to migrate to cooler climates. The Madagascan sunset moth ( Chrysiridia rhipheus ) has migrations of up to thousands of individuals, occurring between the eastern and western ranges of their host plant, when they become depleted or unsuitable for consumption. [17] [18] The hummingbird hawk-moth ( Macroglossum stellatarum ) migrates from Africa and southern Asia to Europe and northern Asia.
In southern India, mass migrations of many species occur before monsoons. [19] As many as 250 species of butterflies in India are migratory. These include members of the Pieridae and Nymphalidae. [20]
Many species Vanessa butterfly are also known to migrate. The Australian painted lady (Vanessa kershawi) periodically migrates down the coast of Australia, [21] and occasionally, in periods of strong migration in Australia, migrate to New Zealand. [21] The painted lady ( Vanessa cardui ) is a butterfly whose annual 15,000 km round trip from Scandinavia and Great Britain to West Africa involves up to six generations. [22] The red admiral ( Vanessa atalanta ) periodically migrates from southern to northern Europe for the summer, [4] although sometimes movement north is observed in early autumn. [23]
The monarch butterfly, Danaus plexippus, migrates from southern Canada to wintering sites in central Mexico where they spend the winter. In the late winter or early spring, the adult monarchs leave the Transvolcanic mountain range in Mexico to travel north. Mating occurs and the females seek 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 the next migratory cycle. The entire annual migration cycle involves around five generations. More detailed information on this migration can be found under monarch butterfly migration.
Short-horned grasshoppers sometimes form swarms that will make long flights. These are often irregular and may be related to resource availability and thus not fulfilling some definitions of insect migration. There are however some populations of species such as locusts ( Schistocerca gregaria ) that make regular seasonal movements in parts of Africa; [2] exceptionally, the species migrates very long distances, as in 1988 when swarms flew across the Atlantic Ocean. [24]
Dragonflies are among the longest distance insect migrants. Many species of Libellula , Sympetrum and Pantala are known for their mass migration. [2] Pantala flavescens is thought to make the longest ocean crossings among insects, flying between India and Africa on their migrations. Their movements are often assisted by winds. [25] [26]
Ladybird beetles such as Hippodamia convergens , Adalia bipunctata and Coccinella undecimpunctata have been noted in large numbers in some places. In some cases, these movements appear to be made in the search for hibernation sites. [2]
Some Oncopeltus fasciatus will journey from northern states and southern Canada to southern states; others will overwinter where they are. [27] Murgantia Histrionica relies on seasonal winds on the Mississippi valley for travel. [27]
Leafhoppers Macrosteles fascifrons and Empoasca fabae rely on seasonal winds on the Missippi valley for travel. [27]
Lepidoptera is an order of insects that includes butterflies and moths. About 180,000 species of the Lepidoptera have been described, representing ten percent of the total described species of living organisms, and placed in 126 families and 46 superfamilies. 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 species-rich orders, along with the Hymenoptera, Diptera, and Coleoptera.
The monarch butterfly or simply monarch is a milkweed butterfly in the family Nymphalidae. Other common names, depending on region, include milkweed, common tiger, wanderer, and black-veined brown. It is amongst the most familiar of North American butterflies and an iconic pollinator, although it is not an especially effective pollinator of milkweeds. Its wings feature an easily recognizable black, orange, and white pattern, with a wingspan of 8.9–10.2 cm (3.5–4.0 in). A Müllerian mimic, the viceroy butterfly, is similar in color and pattern, but is markedly smaller and has an extra black stripe across each hindwing.
Vanessa atalanta, the red admiral or, previously, the red admirable, is a well-characterized, medium-sized butterfly with black wings, red bands, and white spots. It has a wingspan of about 2 inches (5 cm). It was first described by Carl Linnaeus in his 1758 10th edition of Systema Naturae. The red admiral is widely distributed across temperate regions of North Africa, the Americas, Europe, Asia, and the Caribbean. It resides in warmer areas, but migrates north in spring and sometimes again in autumn. Typically found in moist woodlands, the red admiral caterpillar's primary host plant is the stinging nettle ; it can also be found on the false nettle. The adult butterfly drinks from flowering plants like Buddleia and overripe fruit. Red admirals are territorial; females will only mate with males that hold territory. Males with superior flight abilities are more likely to successfully court females. It is known as an unusually calm butterfly, often allowing observation at a very close distance before flying away, also landing on and using humans as perches.
The bogong moth is a temperate species of night-flying moth, notable for its biannual long-distance seasonal migrations towards and from the Australian Alps, similar to the diurnal monarch butterfly. During the autumn and winter it is found in southern Queensland, western New South Wales, western Victoria, and also in South and Western Australia. Adult bogong moths breed and larvae hatch during this period, consuming winter pasture plants during their growth. During the spring, the moths migrate south or east and reside in mountains such as Mount Bogong, where they gregariously aestivate over the summer until their return towards breeding grounds again in the autumn.
Vanessa cardui is the most widespread of all butterfly species. It is commonly called the painted lady, or formerly in North America the cosmopolitan.
The green darner or common green darner, after its resemblance to a darning needle, is a species of dragonfly in the family Aeshnidae. One of the most common and abundant species throughout North America, it also ranges south to Panama. It is well known for its great migration distance from the northern United States south into Texas and Mexico. It also occurs in the Caribbean, Tahiti, and Asia from Japan to mainland China. It is the official insect for the state of Washington in the United States.
Pantala flavescens, the globe skimmer, globe wanderer or wandering glider, is a wide-ranging dragonfly of the family Libellulidae. This species and Pantala hymenaea, the "spot-winged glider", are the only members of the genus Pantala. It was first described by Johan Christian Fabricius in 1798. It is considered to be the most widespread dragonfly on the planet with good population on every continent except Antarctica although rare in Europe. Globe skimmers make an annual multigenerational journey of some 18,000 km ; to complete the migration, individual globe skimmers fly more than 6,000 km —one of the farthest known migrations of all insect species.
Ophryocystis elektroscirrha is an obligate, neogregarine protozoan parasite that infects monarch and queen butterflies. There are no other known hosts. The species was first discovered in Florida, around the late 1960s. Since then, it has been found in every monarch population examined to date, including monarchs sampled in North America, Hawaii, Australia, Cuba, and Central and South America.
Animal migration is the relatively long-distance movement of individual animals, usually on a seasonal basis. It is the most common form of migration in ecology. It is found in all major animal groups, including birds, mammals, fish, reptiles, amphibians, insects, and crustaceans. The cause of migration may be local climate, local availability of food, the season of the year or for mating.
Insect winter ecology describes the overwinter survival strategies of insects, which are in many respects more similar to those of plants than to many other animals, such as mammals and birds. Unlike those animals, which can generate their own heat internally (endothermic), insects must rely on external sources to provide their heat (ectothermic). Thus, insects persisting in winter weather must tolerate freezing or rely on other mechanisms to avoid freezing. Loss of enzymatic function and eventual freezing due to low temperatures daily threatens the livelihood of these organisms during winter. Not surprisingly, insects have evolved a number of strategies to deal with the rigors of winter temperatures in places where they would otherwise not survive.
The Australian painted lady is a species of butterfly mostly confined to Australia, although westerly winds have dispersed it to islands east of Australia, including New Zealand. Debate surrounds the taxonomy of this species. Some believe that the Australian painted lady should be a subspecies of the painted lady due to the similarity in lifestyle and behaviour. Furthermore, the painted lady is found around the globe, but Australia is the only location in which it varies enough to be considered a separate species.
Many populations of Lepidoptera 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.
Danaus erippus, the southern monarch, is a milkweed butterfly in the family Nymphalidae. It is one of the best known butterflies in South America. Its genome is nearly identical to D. plexippus, but the two are incompatible, and therefore considered separate species.
Monarch butterfly migration is the phenomenon, mainly across North America, where the subspecies Danaus plexippus plexippus migrates each summer and autumn to and from overwintering sites on the West Coast of California or mountainous sites in Central Mexico. Other subspecies perform minor migrations or none at all. This massive movement of butterflies has been called "one of the most spectacular natural phenomena in the world".
Commercial butterfly breeding or captive butterfly breeding is the practice of breeding butterflies and moths in controlled environments to supply the stock to research facilities, universities, zoos, insectariums, elementary and secondary schools, butterfly exhibits, conservation organizations, nature centers, individuals, and other commercial facilities. Some butterfly and moth breeders limit their market to wholesale customers while other breeders supply smaller volumes of stock as a retail activity. Some small scale and larger scale breeders limit their businesses to the provision of butterflies or moths for schools. Others provide butterflies to be used and released in commemorative events. The release usually occurs in the natural range of the butterfly.
Altitudinal migration is a short-distance animal migration from lower altitudes to higher altitudes and back. Altitudinal migrants change their elevation with the seasons making this form of animal migration seasonal. Altitudinal migration can be most commonly observed in species inhabiting temperate or tropical ecosystems. This behavior is commonly seen among avian species but can also be observed within other vertebrates and some invertebrates. It is commonly thought to happen in response to climate and food availability changes as well as increasingly due to anthropogenic influence. These migrations can occur both during reproductive and non-reproductive seasons.
Lincoln Pierson Brower was an American entomologist and ecologist, known for his work on monarch butterflies, chemical ecology and conservation.
Migration, in ecology, is the large-scale movement of members of a species to a different environment. Migration is a natural behavior and component of the life cycle of many species of mobile organisms, not limited to animals, though animal migration is the best known type. Migration is often cyclical, frequently occurring on a seasonal basis, and in some cases on a daily basis. Species migrate to take advantage of more favorable conditions with respect to food availability, safety from predation, mating opportunity, or other environmental factors.
Pteromalus cassotis is a species of parasitic wasp in the family Pteromalidae that parasitizes the chrysalides of monarch butterflies. They are gregarious parasitoids, meaning a single female lays many eggs in a single host. Research into this species has documented that up to 425 adult wasps can emerge from a single chrysalis. The wasps have a heavy female bias, averaging 90% female. Maximum entropy models suggest that the natural habitat of this species encompasses the continental United States, southern Canada and parts of Mexico; areas inhabited by the caterpillars of monarch butterflies, which are the larvae's hosts.
Myron P. Zalucki is an Australian professor emeritus of entomology at the University of Queensland (UQ). Zalucki is a Fellow of the Entomological Society of America, a member and secretary of the Council of the International Congresses of Entomology, and a co-editor of the Annual Review of Entomology.
| Biological swarming |  | |
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| Animal migration | ||
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