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MONARCH BUTTERFLY.
Term Paper ID:21850
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Essay Subject:
Metamorphosis, classification, features, flight, defenses, migration, habitats, mating, preservation.... More...
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10 Pages / 2250 Words
11 sources, 36 Citations,
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Paper Abstract:
Metamorphosis, classification, features, flight, defenses, migration, habitats, mating, preservation.
Paper Introduction:
The Monarch Butterfly (Danaus plexippus)
The monarch butterfly, Danaus plexippus, is a widespread insect species. In North America, it is a most characteristic large, ornate butterfly. There has even been an effort in the United States to adopt the monarch as the national insect. Moreover, D. plexippus is the only insect listed by the Bonn Convention for the Conservation of Migratory Species of Wild Animals. In fact, the extraordinary attention that the butterfly has received over the years has led some authors to doubt whether it is justified. The monarch butterfly certainly is not endangered; actually, relatively large numbers of the organism exist. Perhaps it is the monarch's combination of intriguing characteristics though, which have made it the focus of so much scientific investigation.
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Upon finding a good location, thecaterpillar spins a "mat of silk and a button, and, finally, in an invertedposition" undergoes the steady process of metamorphosis.[xv] At first, thechrysalis is about an inch long and pale green with gold spots. During late summer, in response to decreasing daylengths, lower temperatures, and the senescence of their larval host plant,the butterflies leave their breeding grounds in the Great Lakes states andnorthern plains. The Butterfly Book. This gives their soft wings timeto mature in sunlight.[xvi] The Danaus subspecies fly with a slow sailing or soaring motion.Their flight, however, has also been described as slow and labored, strongand rapid, and lazy. "Evolution of Homeotic Gene Regulation and Function in Flies and Butterflies." Nature 372 (December 1, 1994): 458-461.-----------------------T. L. M. Inaddition, remigration may also be influenced by the amount of energyretained by each individual adult butterfly while overwintering.[xxxiii]Eventually, over a sequence of several generations, monarch butterfliesutilize most of North America's continental area. There has even been an effort in the United States to adopt themonarch as the national insect. It isalso found in both Central and South America. Those adults that eventually arrive at the overwinteringsites may be three or four generations removed from the spring migrantsthat originally left.[xxvi] These traveling and overwintering activitiesmake exceptional demands on the monarch butterfly's system. This process essentially involvessmall, worn males in poor condition mating with large females in goodcondition. Hence, the monarch and viceroy butterflies form a Mullerian(formerly described as Batesian) mimicry complex.[xix] Yet another intriguing feature of the monarch butterfly involves itsmigratory behavior. However, since it cannot be considered atall rare, concern over its conservation seems to have centered around itsNorth American life cycle. In California, there are apparently twodifferent kinds of overwintering colonies: The short duration roostingcolonies and the long-term roosting colonies. Moreover, D. In South America, itgenerally inhabits areas north of the Amazon (i.e., Brazil, Venezuela,Colombia, and Ecuador). Perhaps it is themonarch's combination of intriguing characteristics though, which have madeit the focus of so much scientific investigation. Endnotes BibliographyAckery, P. The insects undergo "complete metamorphosis."[i] Female adults layeggs which give rise to larvae, or caterpillars. These bands are either bright yellow or greenish-yellow, and shiny black. While thespecies itself may not be threatened, the gatherings--which involve much ofthe entire North American monarch population--could be. Gates, & S. It has also been recorded from the Solomon Islands westward to theMoluccas. Moreover, various localities in California have alsomoved to protect their monarchs. N. Urquhart (196 ) mapped themigratory routes. This phenomenon represents a classic example of longdistance dispersal in insects.[xx] The monarch cannot tolerate frost.Therefore, in certain regions, it migrates to overwintering areas.Although in Central America, northern South America, and the Antilles,there are non-migratory monarch populations, the butterfly is an annualmigrant in North America and parts of Australia.[xxi] Monarch bodiescontain a magnetic "biosynthetic compass."[xxii] This compass gives themthe ability to orient to the Earth's natural geomagnetism. W. I. The United States' overwintering sites are threatened byslightly different pressures. The monarchs' generally prefer open, sunny locations. Indeed,the California city of Pacific Grove calls itself "Butterfly Town,U.S.A.."[xxix] Several of the California sites comprise groves ofintroduced Eucalyptus trees. Behler, "The Trans-Gulf Express," WildlifeConservation 96 (May-June, 1993): 8.J. Eventually, the male deposits a spermatophore (sperm-containing sac) into the female's bursa copulatrix. In addition, they drink from puddles and streams. By impacting positively on local economies tourism willemphasize the insects' inherent worth.[xxxvi] While the monarchs are in no danger of becoming extinct they stillneed to be preserved. In both Mexico and the United States, overwintering sitesare threatened, albeit by different pressures. Many of theMexican sites face pressures from logging. However, both the migratory and reproductive behavior ofthe butterflies are influenced by environmental phenomena. The butterfly is also found in the West Indies andthe Galapagos Islands. S. Thebutterflies are polygeoneutic. Wintering butterflies areknown to shift their positions. The trees protect the butterflies from climate extremes.Despite the sheltering effects of the forest though, monarchs do not spendthe winter in a state of dormancy. Garden City, NY: Doubleday, Doran & Company, Inc., 1931.New, T. The northern extent of its Pacific domain lies around thePhilippines and Taiwan. Monarch larva usually eat their way out of the egg. These larvae then grow bya series of moults, or instar stages, and eventually transform into aresting stage (i.e., the pupa or chrysalis). (1983) to call the gatherings an endangered phenomenon. This process ismarked by the appearance of an irregular transverse slit. Toronto, Canada: University of Toronto Press, 196 .Warren, R. Thesediurnal Lepidoptera comprise approximately 15 inter-tropical species. J., & Chippendale, G. The larvae have a voracious appetite.Upon hatching, they may even consume portions of unhatched eggs.[xiv]Normally though, the caterpillars feed almost exclusively on milkweeds.This nourishment allows them to grow rapidly. Perhaps in both areas though, the key to compatibility betweenconservation efforts and the local human population lies in tourism. Acting through the neuroendocrinesystem, these phenomena apparently synchronize reproductive activity andmigration with the availability of the major host plant, Asclepiassyriaca.[xxiii] Overwintering males have mature testes and may mate soonafter reaching their wintering sites. W., Nagy, L., Selegue, J., Gates, J., & Carroll, S. The adult butterfly, however, is typically orange andblack.[xii] The upper surface of the wings is bright reddish, with bordersand veins which are broadly black. & Behler, D. Rather, monarch populations mightbecome local and nonmigrating.[xxxv] In response to such concerns, various efforts have been made towardsconservation. These included the following: (1) gliding flight; (2)cruising flight; (3) speed flight; (4) prenuptial flight; and (5) socialflight. The distance traveled by remigratingbutterflies depends upon both climatic and geographic factors. These variations typicallyrepresent some attempt to make optimal use of seasonally availableresources within a given organism's habitat.[ii] The monarch belongs to the Danainae group of butterflies. Nagy, J. These migrations are actually part of the monarch's life cycle. They maytherefore be found around gullies. One recent sighting occurred in Spain.[xi] The monarch is a polytypic species; hence, it displays a combinationof features. Milkweeds possess a whitesap that contains numerous chemical substances which are either poisonousor distasteful to animals. R., & Vane-Wright, R. The butterfly egg is about equal in size to the head of a pin and isovate-conical in shape. Moreover, the gravid females usuallydeposit their eggs en route. These compounds are poisonous to predatorybirds. plexippus is established on many ofthe Pacific Islands. Only within the shelteringbranches of these isolated forest groves can they survive through thewinter. R. L. Vane-Wright, Milkweed Butterflies: TheirCladistics and Biology (London, UK: The British Museum ofNatural History, 1984), 67.Ibid.F. The Monarch Butterfly (Danaus plexippus) The monarch butterfly, Danaus plexippus, is a widespread insectspecies. They are oftenfound in areas of secondary vegetation (i.e., around river margins or inempty lots) rich in asclepiad flora. These monarchs overwinter ina relatively narrow altitudinal band between roughly 9,5 and 1 ,8 feet. New York: Oxford University Press, 1991.Ross, G. The Monarch Butterfly. M. Selegue, J. "Effect of Photoperiod and Temperature on Reproduction of the Monarch Butterfly, Danaus plexippus." Journal of Insect Physiology 22 (1976): 1565-1568.Brown, J. D. "Biology and Conservation of the Monarch Butterfly." American Scientist 83 (March-April, 1995): 189-19 .Holland, W. In just 15 days though, the insects may attaina weight of 1.5 grams (i.e., 15 milligrams). R. Flowers are very attractive to theinsects. Eventuallythough, it turns a dark green to dark brown. This effect can impact negatively upon monarchpopulations. In late winter and early spring, the butterfliespractice negative-assortive mating. A. Unfortunately though, evenmoderate thinning reduces a forest's ability to retard the escape ofradiation at night. In California, habitat destruction occursprimarily as a result of coastal land development. Temperature andphotoperiod affect ovarian development. & Herman, W. Others include planted areas containingconifers, Monterey pines (Pinus radiata) and Monterey Cypress (Cupressusmacrocarpa). The insect also occurs in Australia; it is mostcommon on the eastern portion of the continent. Pacific Grove, for example, has enactedan ordinance protecting the butterflies from molestation. The region contains forests of oyamel fir (Abies religiosa). It has yet to be determined what nutrients arecarried over from the larval stage, and which are consumed in the adultstage.[xxvii] There are nine or ten winter monarch colonies in Mexico.[xxviii] Thefive major sites lie within an area of about 5 square kilometers and arerestricted to a few isolated mountain ranges. Urquhart, The Monarch Butterfly (Toronto, Canada:University of Toronto Press, 196 ), 62.D. J. In fact, the extraordinary attention that the butterfly hasreceived over the years has led some authors to doubt whether it isjustified. There is really no logical reason for all of the attention that themonarch butterfly has received. Holland, The Butterfly Book (Garden City, NY: Doubleday,Doran & Company, Inc., 1931), 68-69.Urquhart, 23.Ibid, 28.Urquhart, 33-39.Ackery & Vane-Wright, 7 , 2 1-2 2."The Food Chain and the Monarch Butterfly," Jama 2 (June 26,1967): 1176.Gibo, 189-19 .J. The decree established a 4 million acre, monarchecological reserve. There the sperm remainuntil the eggs pass down the female monarch's oviduct, and fertilizationoccurs.[xxxii] After mating, monarch butterflies begin their spring remigration.These migrants rarely feed or roost. After it has consumed an enormous amount of food, the monarchcaterpillar leaves its milkweed plants and begins to look for a suitableplace to turn into a chrysalis. The small males are able to accomplish this feat through aerialcapture and takedown mating tactics. plexippus has been recorded in Britain and western continentalEurope. The monarch butterfly certainly is not endangered; actually,relatively large numbers of the organism exist. It occurs from Hawaii to New Zealand and NorfolkIsland. Butterfly Conservation. Furthermore, this reserve has a total of fiveconservation centers. According to Brower andMalcolm (1989), forest exploitation in Mexico provides a major means ofsurvival for a large part of the local human population. In1986, Mexico protected its monarch overwintering sites through apresidential decree. Warren, L. Among certain female monarchs thoughthe ovaries remain immature and thus remain in a state of reproductivediapause.[xxiv] Diapausing adults do not mate until spring. Thecommon name for the insects is the "milkweed butterflies."[iii] Thisderives from their widely exploited host plants. London, UK: The British Museum of Natural History, 1984.Barker, J. In both cases,however, tourism may ultimately serve to protect the butterflies'interests. "Migration of the Monarch Butterfly, Danaus plexippus: Energy Sources." Journal of Insect Physiology 2 (July 1974): 1117-1129.Culotta, E. Newly hatched larva weightonly about .54 milligrams. Researchers believe that by feeding onmilkweeds, the butterflies may also obtain the sap's ability to repelpotential predators.[iv] At the present time, the monarch butterfly is denoted by thescientific name, Danaus plexippus.[v] The Danaus subspecies isdistinguished from most other Danaine butterflies by the fact that themales are unable to synthesize certain male pheromones.[vi] Thus, as themonarchs have evolved, the role of chemical communication during mating hasdiminished.[vii] Danaus originated in the New World, and spread from South Americainto North America about 1.75 million years ago.[viii] However, themonarch is a well-known migrant; it has even been nicknamed "thewanderer."[ix] From its overwintering sites in California and Mexico, itexpands throughout much of North America south of 5 ?N latitude. Luckily though, the butterfly has evolved aremarkable mechanism for avoiding predation. The overwintering gatherings have beendescribed as "spectacular aggregations," where "tens of millions" of thebutterflies "coalesce."[xxxiv] Such recognition eventually led Wells etal. Butterflies, in general, show a great diversity of biologicalfeatures. Milkweed Butterflies: Their Cladistics and Biology. However, itis now known that the viceroy butterflies, like the monarchs are alsodistasteful. Inaddition, other adaptive behaviors employed by monarch butterflies includeraising their body temperature by shivering and dissipating excess heatenergy by ascending into the cool mountain air.[xxx] Towards the end of overwintering, the female monarch butterflies'oocytes begin to mature. Holding the female firmly, the malethen inserts his long needle-like aedeagus into the female's ductuscopulatrix. A. N. Barker & W. The most important of these probably involve the organism's lifecycle. Brown & G. It is knownthat the organisms utilize stored lipids as their primary energy source.However, the nature of these lipids and their derivation remainincompletely understood. Ross & D. The adult monarch butterfliestypically emerge during daylight hours. For example, they may engage in short termmovements to either increase or decrease their exposure to sunlight. During midsummer, when temperatures range between7 ?F and 9 ?F, development occurs rapidly: Under such conditions it maytake only three to four days for an egg to hatch. R. Herman, "Effect of Photoperiod andTemperature on Reproduction of the Monarch Butterfly, Danausplexippus," Journal of Insect Physiology 22 (1976): 1565-1568.Brown & Chippendale, 1117-1118.Brown & Chippendale, 1117-1118.New, 154.Brown & Chippendale, 1117-1118.E. plexippus is the only insectlisted by the Bonn Convention for the Conservation of Migratory Species ofWild Animals. In North America, it is a most characteristic large, ornatebutterfly. Shortly after suchdiscoloration, the adult butterfly's bright orange wings become visiblethrough the chrysalis' transparent skin. The preservation of this natural resource might evenrequire a cooperative effort involving both the United States and Mexico.Clearly, the monarch's protection merits such effort. Culotta, "The Case of the Missing Monarchs," Science 256 (May29, 1992): 1275.New, 156.Gibo, 189-19 .Gibo, 189-19 .Urquhart, 52.Brown & Chippendale, 1117-1118.New, 156.Ibid., 154.Ibid, 156.----------------------- 3 In fact, researchers have suggestedthat the female monarch butterflies have "little choice in thematter."[xxxi] Using well-developed, jaw-like abdominal claspers, the maleobtains a secure grasp on the female. Bothenable the monarch butterfly to escape in space and time from unfavorableenvironments.[xxv] In the United States, there are two distinct monarch populations.The eastern butterflies overwinter mainly in Mexico; whereas, western D.plexippus migrates to the California coast. By feeding on the milkweed, and selectively storing suchsubstances, the monarch caterpillar is able to repel mostinsectivores.[xviii] Moreover, the chemical defenses are believed to alsocarry over into the adult forms. I. The monarch has actuallybecome a "very conspicuous element of the south-west Pacific butterflyfauna."[x] Furthermore, the butterfly has moved east from North Americaalso. InCalifornia, there are at least 4 significant overwintering sites. A. A. Urquhart (196 ) described five distinct monarchflight patterns. The sap of the milkweed plantcontains digitoxin glucosides. Chippendale, "Migration of the MonarchButterfly, Danaus plexippus: Energy Sources," Journal of InsectPhysiology 2 (July 1974): 1117-1118.Ackery & Vane-Wright, 7 , 2 1-2 2.G. In spring, the monarchs then re-emerge to populate the nation'sfields and meadows. The monarch embryo's rate of development dependslargely on temperature. Variations on this basic pattern generally occureither between butterfly groups or species. Wells et al.(1983) warned that, if monarch numbers were substantially reduced, thephenological event might not occur. J. It is during the chrysalisstage that the organism's body is broken down and reorganized into theadult butterfly form. It may bethat migration and diapause are equivalent physiological adaptations. "The Trans-Gulf Express." Wildlife Conservation 96 (May-June, 1993): 8."The Food Chain and the Monarch Butterfly." Jama 2 (June 26, 1967): 1176.Urquhart, F. New, Butterfly Conservation (New York: Oxford UniversityPress, 1991), 23-24.Ibid.P. Carroll,"Evolution of Homeotic Gene Regulation and Function in Flies andButterflies," Nature 372 (December 1, 1994): 458.Gibo, 189-19 .New, 154.Ibid., 33.Gibo, 189-19 .Ibid.W. F. Its bright colors serve to alertpredators to the organism's toxicity. S. Hence, every year, monarchs produce severalbroods of young. Gibo, "Biology and Conservation of the Monarch Butterfly,"American Scientist 83 (March-April, 1995): 189-19 .R. Moreover, the butterfly has "two rowsof white spots on the outer borders" and "two rows of pale spots ofmoderately large size across the apex of the fore wings."[xiii] In malesthe wings are less broadly bordered with black than in females. Moreover, D. The fragile butterflies travel long distances towait out the winter in a few selected sites. In the past, researchers have evenhypothesized that the similarly colored viceroy butterflies were attemptingto repel predators through their resemblance to the monarch. Rather, they have to work to improvetheir chances of survival. J. The butterflies normally live below3 feet, although they have been recorded at much higher elevations(Ackery 7 , 2 1-2 2).[xvii] As an insect, Danaus plexippus is one ofthe links in the food chain. Ackery & R. "The Case of the Missing Monarchs." Science 256 (May 29, 1992): 1275.Gibo, D. The caterpillarshave a shiny black head and black, fleshy thread-like appendages. Theircoloration is banded. F.
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