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 بحث حول النمل القاطع لأوراق الشجر بالانجليزية

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كاتب الموضوعرسالة
فجر الرحيل
المدير العــــام
المدير العــــام


ذكر
الحمل التِنِّين
عدد المساهمات : 1459
تاريخ الميلاد : 16/04/1988
تاريخ التسجيل : 20/03/2010
العمر : 28
المزاج المزاج : رايق

مُساهمةموضوع: بحث حول النمل القاطع لأوراق الشجر بالانجليزية   الثلاثاء نوفمبر 23, 2010 10:43 am

Leaf-cutting Ants

Grant Erickson
Intro



One of the most little known species of ants in NorthAmerica is the leaf-cutter ant. This ismainly because it lives in tropical environments and it is not aggressive toanimals or humans if not disturbed. Theleaf cutting ant is a social insect. Alone the ant is virtually helpless but with the colony it can be athing feared by animal and human alike. The leaf-cutting ants have a very important role in the tropicalforest. They create and manipulate theenvironment around them. They also can do major damage.

Theleaf-cutting or fungus-growing ants are distributed from northern Texas tocentral Argentina. These ants are injurious since they cut the green vegetationfrom trees, shrubs and crops, and carry it into the nest, where they cultivatefungi on it. They have been known to denude a tree or ornamental plants in onenight. It has been estimated they do $1billion damage per year in North and South America today, these ants stillcause millions of dollars in crop losses in many South American countries.Although primarily an agricultural pest, this insect on occasion may invade thehome for cereals. In the United States, the Texas leaf-cutting ant, Atta texana , occurs in Texas and Louisiana.This ant is believed to cause a total yearly loss of $5 million in the UnitedStates (unison services. 1998).

There are about 9,500 namedspecies of ants. These ants are dividedinto 16 sub families and 300 genera, all which belong to the family calledFormicidae, the family of ants (Hoyt. 1996). The leaf cutting ant belongs to the genus called Atta. There are fifteendifferent species of Atta and all arelimited to the new world (Holldobler & Wilson, 1994).


Thesis



Theleaf-cutter ant looks pretty much like a regular ant in North America exceptthat it is a little bigger than most ants. Looking at the ant in the untrained eye a person usually perceives thatit is a primitive organism. Looks can bedeceiving. The leaf-cutter ant is acomplex superorganism unique social, environmental, and food gatheringbehavior.
Anatomy



The anatomy ofthe leaf-cutter ant is pretty simple.

It has a one segment "waist" (pedicel) betweenthorax and abdomen. Sharp spines on waist and backward from head. Antennae11-segmented very long and elbowed without distinct club. The legs are verylong. This ant can be light to dark reddish brown (Smith. 1997).

The leaf-cutter at is just likeother ants in many areas in appearance. The ant has a hard exoskeleton to which the muscles are attached. It also protects the internal organs. The main feature of the ant is its head. The large solders have huge serrated bladeswhich they can have up to 0.5 cm space between the mandibles. The size range can be from 1/16 to ½ an inchdepending on the type of species. Theants are divided up into three different types according to size. Minima (<5mm long), media (>5mm long)and soldiers (a distinct class with oversized head and mandibles and a totalbody length of more then 13mm) (Whitehouse & Jaffe 1996). The averageworker leaf-cutter ant lives from 4-6 months (Howard, Henneman, Cronin, Fox,Hormig. 1996). The worker ants commonly perform superhumanfeats.

If we magnify the operation to human scale, so that anant’s 6-millimeter length grows into a meter and a half, the forager runs alongthe trail for a distance of about 15 kilometers at a velocity of 26 kilometers anhour. Each successive mile (to convertto familiar Anglo-American sports distances) is covered in 3 minutes and 45seconds, about the current human world record. The forager picks up a burden of 300 kilograms or moreand speeds back to the nest at 24 kilometers an hour – hence 4 minute miles(Holldobler & Wilson, 1994).

The queen isthe largest of the ants and can reach length larger than ½ an inch and her lifespan can be 10 years or more (Smith. 1997). The queen has wings and when she decides to leave the nest she carries asmall pellet of mycelium (the fungus) in a special pocket on her head. When a new nest is found, the mycelium isused to start to grow food again. The colony growth is slow at first but soonproceeds rapidly and reaches maturity in about 5 years.


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فجر الرحيل
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المدير العــــام


ذكر
الحمل التِنِّين
عدد المساهمات : 1459
تاريخ الميلاد : 16/04/1988
تاريخ التسجيل : 20/03/2010
العمر : 28
المزاج المزاج : رايق

مُساهمةموضوع: رد: بحث حول النمل القاطع لأوراق الشجر بالانجليزية   الثلاثاء نوفمبر 23, 2010 10:45 am

The Nests – Fungus garden


The nests of the leaf cutting ant can get up to 200 square metersin length and 6 metersdeep. Up to 5 –8 million ants can livein one nest (Holldobler & Wilson, 1994). The ants nests have many entrances and exits which facilitate travel andair supply into and from the nest. Someunderground pathways can reach up to 200 meters in length. The nest consist of many chambers--2000 in an average sizedcolony. Each chamber is 8 to 12 inches (200-300 mm) in diameter. Nest building raises ahuge mound of soil. Ants constructing an average-sized mound carry 88 tons (80,000 kg) of soil to thesurface (Fogel R. 1997). Under theground there are many paths which lead to multiple cavities in which fungusgardens grow. The fungus garden is a spongy mass like a sponge with lots ofspaces. The leaf-cutting ant has amutualistic relationship with the fungus, which they cultivate on fresh plantmaterial. The species of fungus used isfrom the basidiomycte family called Lepiotaceae. Some researchers say that all gardening antscultivate a single form of the fungus species, Leucocoprinus gongylophorus (Hoyt 1996). Leaves are brought in by workers and thenreduced to a pulp and incorporated with their saliva and fed to the fungus.These fungi produce swollen hyphae (gongylidia), bunches of which are known asstaphylae. These provide food for theants and their larvae (Weber 1972). Forthe best productivity, the fungus garden must have a structure that combines alarge area for the production of staphylae (the ant’s food) with the smallestchamber volume which can be maintained and with accessibility to the workers(Bass & Cherrett 1996).. Most of thefungus garden can be only accessed by minima workers because the smallpassageways in the fungus limit the size of ant that can pass through. In the fungus garden there is more surfacearea on the inside than the outside and there is more fungus (staphylae) on theinside than the outside. Thus there is amuch greater need for small ants in the fungus garden than large ants. Since the outer surface can be accessed byall ants, there is a much greater harvesting pressure on it than the interiorsurface of the fungus garden. Theoutside of the garden appears to be heterogeneous. Another important feature of the fungusgarden is how long the substrate material will support the growth of thefungus. It is found that fungal gardenshave a life cycle of 7 weeks to four months. The length of time the fungus can grow on the substrate is related tothe season the type of substrate the ants use. The outside of the fungus garden is heterogeneous. The upper part is a green-gray color withlarge cells, and this is a young garden where most of the fresh substrate isadded. Fungus gardens get older from thetop down. The further down you go on thegarden, the grayer it will look and the cells will become smaller because ofthe pressure from the fungus on top. Eventually the holes become so small that minima ants can not haveaccess to the interior of the garden. Old gardens have thinner walls then new gardens. Since the walls become thinner and the holesbecome smaller the surface are per unite of volume becomes greater in oldergardens. On an average, 74% of the totalgarden surface area is internal. Theinterior cells of a fungus garden have an average area of 2.17 mm square and acircumference of 5.71 mmsquare. About 90% of the ants found inthe interior of the fungus garden were minima. When the ants start to put down new substrate, the first staphylae isproduced in about 4-5 days. The bestproduction comes in about 20-30 days after substrate is added. Smaller cavities have more staphylae per unitare than larger ones. Therefore theolder the garden becomes, the more food the ants get until about 7 weeks laterwhen the fungus runs out of substrate. As you can begin to see, there is two antagonistic things working forand against the ants. The ants want tomaximize production (keep cells small so more staphylae grow per unite of areaand to maintain a high humidity) but also they want to keep the gardenaccessible for all workers (Bass and Cherrett 1996).
Afterreading the above paragraph you are left with some questions. Do the leaf-cutting ants have any mechanicalaction on the fungus to improve its productivity? Does the fungus garden need to me tendedafter substrate is given to the fungus? I will answer these questions using (Bass & Cherrett 1996). The presence of workers on the fungusstimulates staphylae production in a number of ways. Workers frequently defecate onto substratethat they have just added to the garden (Quinlan & Cherrett 1977). It turns out that the fungus lacks enzymes todegrade protein so it can’t receive any nitrogen compounds from thesubstrate. The ant feces contain ammoniaand a mixture of amino acids (Boyd & Martin 1975) which supplies the needof the fungus. The ants also prune thefungus when they eat the staphylae. Studies have shown that about four days after pruning, the fungus growsmore staphylae then if it hadn’t of been pruned. If a fungus garden is not pruned, then largewhite growths appear on the fungus surface. This coincides with low worker populations and a small number ofstaphylae. The ants eat staphylae whenthey are of medium size. Old staphylaeare large. It is interesting that if thefungus is not pruned, staphylae is not produced. This show the implication that theleaf-cutting ant and the fungus have evolved in such a way that both can notlive without the other. How does thefungus keep from being totally consumed by the ants? It turns out that most of the hyphae of thefungus is mixed up with the inedible fragments of vegetation. The hyphae becomes available to the ants onlywhen it grows out of the vegetation to produce the edible staphylae (Bass &Cherrett 1996). As we can see, thefungus ant relationship is a unique and complex system of controls anddependencies. So even though there isgreater harvesting pressure on the outside of the fungus garden, the more theants prune and eat the fungus, the more the fungus responds and producesnutrient staphylae.


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[ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط]


الرجوع الى أعلى الصفحة اذهب الى الأسفل
فجر الرحيل
المدير العــــام
المدير العــــام


ذكر
الحمل التِنِّين
عدد المساهمات : 1459
تاريخ الميلاد : 16/04/1988
تاريخ التسجيل : 20/03/2010
العمر : 28
المزاج المزاج : رايق

مُساهمةموضوع: رد: بحث حول النمل القاطع لأوراق الشجر بالانجليزية   الثلاثاء نوفمبر 23, 2010 10:46 am

Reproduction and the colony


Thereproduction and initiation of a colony is very similar in all species of the Atta tribe. Mating season is usually around May or Junebut the environment at the time has a major influence on mating times. The reproduction process always begins withthe nuptial flights (Holldobler & Wilson, 1994). “Some species such as Atta sexdens, hold the flights in the afternoon, while others suchas Atta texdens of the southwestUnited States, conduct them in the darkness of night” (Holldobler & Wilson,1994). While beating their wings, theheavy females meet and mate with as many as 5 or more male in succession. While in the air, each queen will receive 200million or more sperm from her mates, who will die within a day or two. She stores the sperm in her spermatheca andit is there the sperm will die for up to 14 years which is the known maximumlifetime of a queen. Each sperm will beused individually to fertilize a single egg. A single queen can produce as many as 150 million daughters which arethe majority of the workers. Some willturn into queens capable of founding a colony on their own. Others will arise from unfertilized eggs tobecome short-lived males. After a queenhas successfully mated, she will descend to the ground and rakes off her wingsat the base. Then she will dig acylindrical hole about 30 cmdeep where at the bottom she widens a room about 6 cm across. She then spits out the packet of fungus shestored in her pouch at the bottom of her mouth onto the floor so her garden canstart. The she lays 3 to 6 eggs. The fungus grows and when she has laid morethen 20 eggs she will put the eggs and the fungus together. All this time the queen is cultivating thefungus by herself. At regular intervalsabout an hour or two she takes a piece of fungus and defecates on it with abrown drop of fecal liquid. In about 40to 60 days the first adult workers emerge (Holldobler & Wilson, 1994).
Allduring this time the queen survives on the energy obtained from the metabolicbreakdown of the wing muscles and fat from her own body. Also at the beginning she eats up to 90% ofher eggs. This puts a lot of pressure onthe queen. Day by day she grows thinnerwhile caught in a race between starvation and creation of enough ants that cansustain her life. With the queen’sresources rapidly running down she must create a perfectly balanced work forceon her first try. In the first crop ofadult workers, there are no soldiers or larger-sized workers. Only the smallest foragers and still smallerworkers who raise the fungi are present When the workers emerge they immediately begin to feed on the fungus andthen dig their way up to the surface and bring leaves to sustain the fungusgarden. The queen now turns into an egg laying machine. All she does is eat and produce eggs whilethe colony does the rest of the work. Asthe colony grows and prospers and size range of workers expands to includelarger and larger forms. When the colonyreaches about 100,000 members, the first full-sized soldiers are present. The colony’s beginning is slow but during the2nd and 3rd years its growth is accelerated. When the colony begins to produce wingedmales it is a sign that the queen is old and soon the colony dies (Holldobler& Wilson, 1994).
Whenthe queen first starts to lay eggs, Holldobler & Wilson (1994) found thatthe heads of the ants produced were in the range of 0.8 to 1.6 millimeters(heads of ants are proportional to body length, the larger the head, the longerthe body). If the heads are greater than1.6 millimeters,the queen will have lost too much energy in producing them and she will diealong with the colony. If the heads areless than 0.8 millimeters, the ant is useless because it is too smallto carry leaves and too small to care for the fungus garden(s). Now you must be asking yourself, how does thequeen know what distribution of offspring to produce first? Holldobler & Wilson (1994) found that itis the size of the colony, not its age that determines that castedistribution. Example, if you took a largecolony of leaf-cutting ants and killed all of the ants except 10,000. The queen would not produce huge soldier antsbut would concentrate on producing small and medium sized ants until the colonyreached a certain size. In essence, bykilling the ants you made the colony young in its size and caste configuration(my example).
Anotherreason for the unique distribution of the roles and sizes of ants is related tophysics and chemistry. In each role ofeach size of ant, Holldobler & Wilson (1994) found that when they measuredcarbon dioxide given off, that the ants minimized the amount of carbon dioxidegiven off. This means that the ant whois suited for the best caste for the job, is the one who gathers the mostvegetation with the least expenditure of energy. The most efficient group of leaf carriersproved out to be the ones whose heads were 2.0 to 2.2 millimeters inwidth. When soldiers were given leafcarrying jobs, they use much more energy.
Thesex of a leaf-cutter ant is very easily determined. If the queen fertilizes an egg it produces afemale and an unfertilized egg produces a male. Since the male progeny come from unfertilized eggs, they are haploid;that is, they inherit one of the mother’s two sets of chromosomes and nothingfrom the father (Hoyt 1996). The femaleon the other hand is diploid. Theyreceive one of the mother’s two sets of chromosomes and the father’s one set(only one set of chromosomes exist in a gamete or sperm).
The key is that one set – thehalf of the genes that daughters get from their haploid father. It is identical to every other set everyfemale gets, and thus the sisters must be at an absolute minimum of 50% relatedto each other. The genes from theirmother, depending on which of the two sets of chromosomes is inherited, may ormay not be the same. On average, basedon chance, sisters share 75 % of their genes with each other – more than 50 %they share with either parent. Thussister ants in a colony can best ensure the survival of their own genes byhelping each other. Males, meanwhile,with only one of the mother’s two sets and nothing from a father, share only 25% of their genes with their sisters, on average, and predictably contributeless labor than females to the colony welfare; their purpose is reproductionthrough a single mating, after which they die (Hoyt 1996).
This is oneof the main differences that separates the ant species from other insects. For all hymenopterans are haplodiploid. Also a difference within hymenoptera is thatthe Atta group is a social insectwhile most hymenopterans are solitary. Now you must be asking yourself, what causes a female to grow into afertile queen instead of a sterile worker? Holldobler & Wilson (1994) said that the deciding factors are environmental rather than genetic.


All the females of a colony possess the same genes withrespect to caste – and any female after conception [as previously mentioned,most ants in the nest are female] can turn into either a queen or aworker. The genes merely provide thepotential to develop into either a worker or a queen. The controlling environmental factors areseveral in kind, varying among species. On is the amount and quality of food received by the larva. Another is the temperature of the nest at thetime the larva is growing up. Stillanother is he physical condition of the queen. If the mother ant is healthy, she produces secretions during most of theyear that inhibit the larva from developing into queens [this is a reason whyonly older nests produce queens and males at the same time]. In this one category the mother deserves thename we have given her – queen, or ruler of the colony. She not only determines whether an offspringwill be male or female, but also assigns caste to her daughters. Yet even here, the workers exercise a kind ofultimate, parliamentary control. Theyalone decide which of their growing brothers and sisters will live or die, andhence they determine the final size and composition of the colony (Holldobler& Wilson 1994).
Theleaf-cutter ant has posed serious problems for evolutionists. For what is the advantage an individual antgains in putting all her energy into the selfless tasks of a colony, from leaf-cuttingto caring for the larva to fighting as a soldier – without ever having a chanceto mate and produce offspring of her own? This question has led evolutionists to one of the secrets of thesuperorganism. “The ants’ success liesin the evolutionary concept of kin selection” (Hoyt 1996). This concept occurs when members of a specieswork for the survival of relatives – genes by descent from a common ancestorrather than for one’s survival of its own offspring (which is called individualselection). This is a very complicatedprocess in which many people have devoted their lives to its study.
Foraging


Thegathering of food by the leaf cutting ants is a complex series of interactionsand communication which I will discuss. The foraging for food first is started from the central nest. Special ants called scouts range off of anttrails in search of food for the nest and if they find food, they start torecruit workers to collect the resource. This sounds simple but the process is actually very complicated. Using Howard, Henneman, Cronin, Fox, andHormig’s research (1996) I will explain the process. When a scout find a food source, the decisionof whether or not to recruit workers is based on the location, quantity, andquality of the source. Also the scoutsexamine resource consistency such as protein, lipid or simple sugarcontent. If a scout finds a familiarresource, it will recruit workers faster then if it found an unfamiliarresource. How much an ant is familiarwith a resource was found to be in direct proportion to the number of times theant physically touched the resource or food. The same goes with the workers. If a scout presence a worker with an unfamiliar resource, it is morelikely to reject it. If the resource isaccepted, the worker ant will follow the special scent trail laid down by thescout to the location of the resource. The time delay for the ants to follow a new type of food can be anegative and a positive. This can carrycosts by the delay in acceptance of a new resource such as food delay,overexploitation, and starvation. Thismechanism can also protect the ants in that the ants know that the food theyare feeding the fungus works but a new type of food can poison the fungus.


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الرجوع الى أعلى الصفحة اذهب الى الأسفل
فجر الرحيل
المدير العــــام
المدير العــــام


ذكر
الحمل التِنِّين
عدد المساهمات : 1459
تاريخ الميلاد : 16/04/1988
تاريخ التسجيل : 20/03/2010
العمر : 28
المزاج المزاج : رايق

مُساهمةموضوع: رد: بحث حول النمل القاطع لأوراق الشجر بالانجليزية   الثلاثاء نوفمبر 23, 2010 10:47 am

Wirth,Beyschlag, Ryel, and Holldobler (1997) studied the cycle of foraging in theleaf-cutter ant and they found some interesting results. They found that on an average, the totalyearly input of collected green leaf material corresponded to1706 to 3,855 meters square offoliage area depending on the size of the nest. The number of leaf fragments collected per day ranged from 9,770 to374,200. During the dry season the antsharvested more leaves than the wet season due to the loss of availability ofgreen leaves during the dry season.. Also the type of material collected during the two seasonsdiffered. During the wet season, greaterquantities of green leaves were collected while during the dry season, nongreen material was collected (fruit parts, stipules, and flower parts). The ants collect resources according to theiravailability during that time. Theamount of material collected also varies with the seasons. During the wet season, more material iscollected. A possible reason for this isthat since during the dry season the ants collect more flowers and fruits whichcontain more energy then leaves, the ants don’t need as much material to feedthe fungus. The rain limits the amountof foraging that can go on during the wet season by physically stopping theants from moving on their paths due to the abundance of water on top of thesoil. This may be important inregulating colony size. The average areaof a leaf fragment carried by individual ants was determined to be 0.79 cm square and with anaverage weight of 5.51 mg. Thescientists discovered that fragment area and weight was determined by the typeof plant harvested. Succulent leaves(which are normally thick) were cut into small pieces (<0.5 cm square) whilefragments cut from glabrous leaves (thin leaves) were often larger than 1.0 cm square. The daily foraging cycle of the leaf-cutterant was also determined. Foragingincreases rapidly during daybreak and remained high during the daylight hoursbut returned to low levels by nightfall. In some colonies, foraging is limited to the night. During the day some types of carpenter ants(especially species Camponotus) guardthe trees the leaf-cutting ants use for foraging. This prevents that Atta foragers from foraging during the day. When nightfall comes the carpenter ants leaveand the leaf-cutter ants forage during the night to make up lost foragingduring the day. Maximum rates of harvestoccur from 3:00pm to 4:00 pm.
Roces,Holldobler, Tautz, Kleineidam, and Krumme found that when leaf-cutting antswere cutting leaves, their metabolic rate was dramatically above their restingrate. It was found that cutting leaftissue use up 31 (31 000 %) times more energy than in a resting state. They also found that the size of the leaf cutdepended on the amount of energy invested. The more energy spent in a short amount of time, the smaller the size ofleaf cut. This is why when cutting atthe stem of a plant, the ants cut such small pieces (personal observation).
H.L.Vasconcelos (1997) found that the number of attacks on a given species wasmainly determined by its abundance in that area. Thus changes in species composition near anant colony will result a change in the type of resources brought into thecolony. His study showed that there isno short term variation in the amount of secondary compounds or leaf nutrientsin response to defoliation of a plant by the ants. The reason why some plants are only partiallydefoliated and some are fully defoliated is that only the preferred leaves arecut by the ants. In large trees theredifferences in light conditions in the canopy which causes changes in the leafstructure and content. Immature treeshave less variation in nutrient and content of its leaves and therefore is morelikely to be totally defoliated than older and larger trees. On the average, 85.7% of attacks on a giventree results in complete defoliation (Vasconcelos 1997).
Defense


Theants have many defense mechanisms and behavior patterns. Some ants guard the nests entrances. In doing this they are usually still and arein the stilt-legged position. Stilt-legged position is when the ant is still and when its head ispointing upward and its mandibles are open. Another defense mechanism is capping. This is when the ants panic because of some enemy and all sizes of antsuse matter to close the nest entrances. Avoiding can lead to their not being a battle. This is when ants avoid each other and one orboth nests leave the feeding site. The armadillos are the mainvertebrate predator of the leaf-cutter ants (Whitehouse & Jaffe 1996). The armadillos dig up the nests to get at theeggs and the many ants tending the nest. As soon as there is a mechanical disturbance of the nest the percentageactivity of soldier ants outside of the nests is increased approximately 49%. The number of small ants decreased by anaverage of 47% on top of the nests (Whitehouse & Jaffe 1996). Thus soldier ants with their large mandiblesare a better deterrent against large enemies then small ants. Leaf-cutter ants must also defend againstother ants and even against ants of its own species. Ant battles are rare but when they occur theyare spectacular. Battles occur when atleast 50 ants are fighting. Fighting isdone by one ant biting the leg or body part of another ant with its mandibles. Fighting usually occurs in balls of ants witha ball having about 14 ants. Ants start dyingusually if the fighting lasts more than one hour. Usually when ants from other nests meet thereis a short skirmish and then avoidance. The ant battle operates on the square law which predicts that is allindividuals are equally vulnerable to attack then the side with the mostattackers will win. Thus many smallerants are more beneficial then a few large soldier ants. Small ants fight but they also lay down scentor territorial markers. It is found thatthe better a nests territory is marked, the more likely the nest will win thebattle. Thus the more small ants a nesthas, the more territory will be marked and more opposition ants will be killed. Also it appears that the large soldier antsare primarily to protect the nest while the small ants and workers fight theintraspecific battles. The substancesthe ants use to mark their territory are hexadecanoic acid heptadecane. Hexadecanoic acid is a special compoundproduced by the metapleural glands and is always being released by theworkers. Heptadecane is produced by theDufours gland and is actively secreted as a territorial marker and also as amalarm pheromone. The overlying theme ofleaf-cutting ant’s defense is to protect its food supply. Even though the ants use avoidance most ofthe time this is viewed as a type of defense so that in the case of a largeconfrontation, many ants can be present on a marked territory (Whitehouse &Jaffe 1996).
Roces,Holldobler, Tautz, Kleineidam, and Krumme found an interesting defensemechanism in the foraging column of the leaf-cutting ants. In the foraging column the minima workers“hitchhike” on leaf fragments carried by the workers. The purpose of this is that the large workerswill defend the small workers from parasitic phorid flies.

Ant on itsEnvironment
Theleaf-cutting ant has a profound effect on its environment. In some areas the leaf-cutting ant is adetermining factor of forest dynamics and composition (Heraldo and Cherrett1997). When a leaf-cutting ant nestmoves into a new environment they immediately start to chew up and move leavesand seeds. Vasconcelos and Cherrett(1997) found that the damage done by leaf-cutting ants negatively affectedseedling survival and growth. They alsonoted that time most dangerous to a seedling was between 3-9 months. Thus the older the seedling becomes, the lesschance it will die from being chewed on by the leaf-cutter ants. The ants have a preferential taste forcertain types of plants. This leads toselectivity and thus the ants can change forest composition. Since the ants mainly go after leaves ofseedlings, populations tend to increase after clearing of mature forest(Heraldo and Cherrett 1997). Thus theants can reduce tree establishment by two ways. They can act as seed predators and seedling predators.
Anotherway that the ants effect the environment (this one can be positive) is throughfacilitated succession. This researchwas done by Brener and Silva (1995). Itwas found that some trees grow preferentially on abandoned leaf-cutter antnests (Bucher 1982). It was found thatbetween the open grass lands and forest there was numerous ant nests. Here there are many seedlings and smallertrees as the forest starts to colonize the savanna. This is where many leaf-cutting ants are (forreasons already described). The woodlandtrees changes the soil which the facilitates the establishment of shrubs whichallows the further survivorship of near by ant nest between the forest andgrass land. As show by Brener andSilva’s (1995) results the ants benefit from direct food availability andbetter habitat conditions and as thenest grows, it promotes changes in soil and nutrient status improvingconditions for the survival and growth of trees. Nitrogen, phosphorus, potassium, magnesium,calcium, sodium, moister, organic carbon, all increased due to ant nests. The scientists found that groves would growlarger and more quickly than those who had no ant nests. Bucher in 1982 found that the effects of thenests last for a long time when it is abandoned.
Communication
Thetype(s) of communication leaf-cutting ants use is still in the process ofresearch. What we do know is thatworkers produce vibrational signals while they are cutting leaves (Roces, Holldobler,Tautz, Kleineidam, Krumme). Thevibrations have two purposes. They actas close-range recruitment signals and it also facilitates the cutting of leaftissue, like a vibrating knife or jigsaw. The plant-borne vibrations producedby the workers are used by other workers in locating the cutting site(s). Roces, Holldobler, Tautz, Kleineidam, andKrumme found that the vibrations mean differently to the ants depending on thesocial context being used. The leaf-cutting ants also produce rapid vibrations,which are audible to humans, the antdoes this by rubbing two abdominal organs –one a sharp scraper which scratchesthe fine ridges on the other. Thevibrations radiate along the ants body all the way to her sickle, serratedmandibles. The mandibles vibrate up anddown at 1,000 Hz at the ant uses one mandible to cut the leaf (Beatman 1995). Rocesand company also found that the leaf-cutting ants carry several thousand chemoand mechanoreceptors but only 12 sensilla that respond to carbon dioxide. These sensilla act as measuring devices whichconstantly measure atmospheric carbon dioxide. The ants can scan spatial and temporal carbon dioxide gradient and usingthis mechanism they can locate the entrances to their nest. It was found that the ant even move theirantennae in such a patter which stimulates the carbon dioxide sensillaeoptimally (Roces, Holldobler, Tautz, Kleineidam, and Krumme).


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ذكر
الحمل التِنِّين
عدد المساهمات : 1459
تاريخ الميلاد : 16/04/1988
تاريخ التسجيل : 20/03/2010
العمر : 28
المزاج المزاج : رايق

مُساهمةموضوع: رد: بحث حول النمل القاطع لأوراق الشجر بالانجليزية   الثلاثاء نوفمبر 23, 2010 10:47 am

Control


Controllingleaf-cutting ants is a major problem is some countries. The structure of the ants’ nests make itextremely difficult to destroy with pesticides and machines. Individual plants can be protected by usinginsecticides such as acephate (Orthene), diazinon or chlorpyrifos (Dursban),but these treatments do not affect the colonies. The Eradicator Fire Ant Eradicator System canbe used on leaf-cutter ants too. It isdesigned to injects vaporized resmethrin. Methyl bromide gas (from Great Lakes Chemical Corporation’s Brom-O-Gas)is very effective against the ants. Butthis is highly toxic to humans, plants, and animals. There is also some concerns about the toxintravelling up ecosystems. Thus you haveto have a special permit to use it. Production of the gas will be terminated at the end of the year2000. Baits and other foods do noteffect the ants because they only eat the fungus. The American Cyanamid Company has developed aunique product called Amdro Leaf-Cutting Ant Bait which is a formulation ofhydramethylnon. It is the most effectiveleaf-cutting ant killer on the market. The ants are attracted to the substance which is spread on the groundand feed it to their fungus. The productpoisons the fungus and it dies along with the ants (Stewart 1982).

Conclusion
Theleaf-cutter ant has become a marvel of cooperation and unselfishness. The ant system has become a collection ofindividual ant that are each specialized in their tasks as the cells of thehuman body and that jointly perform the task of keeping the nest alive. They do precisely the right things for theirown survival. Guided by instinct, thesuperorganism responds adaptively to the environment. Humans depend on the ants for their verysurvival but the ants do not depend on us. For a while at least, they will help to hold the world in balance to ourliking, and they will serve as a reminder of what a wonderful place it was whenwe arrived in north and central America. There is still many more answers unsolved about the Atta tribe. In time we willlearn more and will be amazed. For whenSolomon said “Go to the ant, thou sluggard, Consider her ways and be wise!”(Proverbs 6:6 – Cool. I am sure it wasmeant to be taken literally.
















Works Cited

Alejandro, G., Brener, F., and Silva, J. 1995. Leaf-cutting ants and forest groves in a tropical parkland savanna ofVenezuela: facilitated succession?. Journal of Tropical Ecology 11: 651-669

Bass, M., and Cherrett.J. M. 1996. Leaf-cutting ants (Formicidae, Attini) prunetheir fungus to increase anddirect its productivity. FunctionalEcology 10: 55-61

Bass, M., and CherrettJ.M. 1996. Fungus Garden Structure in the Leaf-CuttingAnt Atta sexdens (Formicidae, Attini). Symbiosis 21: 9-24

Boyd, N.D. &Martin, M.M. (1975) Faecal proteinasesof the fungus-growing ant Atta texana: their fungal origin and ecological significance. Journal of Insect Physiology 21, 1815-1820

Bucher, E. H. 1982. Chaco and caatinga – South American arid savannas, woodlands andthickets. Pp. 48-69 in Huntley, B. &Walker, B. (eds). Ecology of tropicalsavannas. Spinger-Verlag, Berlin

Beatman, John. 1995. Vibrant ants. Discover 4: 12-13.

Fogel, Robert. “Antgardens” April 21, 1997. Available : [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط]
Holldobler, Bert., andEdward O. Wilson. Journey to the Ants, AStory of Scientific Exploration. London, England: The Belknap Press of Harvard University PressCambridge, 1994.

Howard. J. J.,Henneman. M., Cronin. G., Fox. J., and Hormiga. G. 1996. Conditioning of scouts and recruits during foraging by a leaf-cutting ant, Atta colombica. Animal Behavior 52: 299-306

Hoyt, Erich. The Earth Dwellers, Adventures in the Land ofAnts. New York: Simon & Schuster,1996.


Quinlan, R.J. &Cherrett, J.M. (1977) The role of substrate preparation insymbiosis between the leaf -cuttingant Acromymex octospinosus EcologicalEntomology 4, 151 -160 (Reich)and its food fungus.

Roces, F., Holldobler,B., Tautz, J., Kleineidam, C., Krumme, S. “Communication, ecophysiology and energetics in leaf cutting ants (Atta).” Date unknown. Available : [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط] -wuerzburg.de/bericht/zoo2/engber.htm#2

Smith, C. “Leaf-Cutting Ants.” 23 March. 1997. Available: [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط]

Stewart, J.W. “Texas Leaf Cutting Ant” Sept. 1982. Available : [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط]

Unison Services. “The Leaf Cutting Ant or Fungus-GrowingAnts.” 4 Jan. 1998. Available : [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط]

Vasconcelos, H.L. 1997. Foraging activity of an Amazonian leaf-cutting ant: responses to changesin theavailability of woody plants and to previous plant damage. Oecologia 112: 370-378

Vasconcelos, H., andCherrett J. 1997. Leaf-cutting ants and early forestregeneration in central Amazonia: effects of herbivory on tree seedling establishment, Journal of Tropical Ecology 13: 357-370

Weber, V.A. (1972)Gardening Ants, the Attines. AmericanPhilosphical Society. Philadelphia.


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[ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط]


الرجوع الى أعلى الصفحة اذهب الى الأسفل
فجر الرحيل
المدير العــــام
المدير العــــام


ذكر
الحمل التِنِّين
عدد المساهمات : 1459
تاريخ الميلاد : 16/04/1988
تاريخ التسجيل : 20/03/2010
العمر : 28
المزاج المزاج : رايق

مُساهمةموضوع: رد: بحث حول النمل القاطع لأوراق الشجر بالانجليزية   الثلاثاء نوفمبر 23, 2010 10:49 am

Whitehouse, M., andJaffe, K. 1996. Ant wars: combat strategies, territory andnest defense in the leaf- cuttingant Atta Laevigata. Animal Behavior 51: 1207-1217

Wirth, R., Beyschlag, W., andRyel, J. 1997. Annual foraging of the leaf-cutting ant Atta colombica in a semideciduous rainforest in Panama. Journal of TropicalEcology 13: 741-757




Some interesting facts that Icouldn’t find a place for in my research paper.

- Bert Holldobler, E.O. Wilson and J.Malcolm Cherrett seem to be the leading researchers in the world who arestudying leaf-cutter ants.
- In a typical leaf-cutter colony, 78% ofthe ants are inactive at any given time.


Memorable Statements.

- The sense that insects belong to adifferent world than ours is shared by many people, and it is a perfectly validfeeling. After all, the search for acommon ancestor of insects and ourselves would take us back more than half abillion years. But insects are very muchof this world, and Homo sapiens is a strange and aberrant creature of recentorigin who has sought to create his own world, apart from that of nature.
- Howard Ensign Evans. The Pleasures of Entomology, 1985.


- It would appear that socialism reallyworks under some circumstances. KarlMarx just had the wrong species.
- Bert Holldobler and Edward O.Wilson. Journey to the Ants, 1994.

- When we compare the motives which bindtogether the societies of humans and of ants, we are forcibly struck by theirsimilarities.
- Caryl P. Haskins. Of Ants and Men, 1945.

تم بحمد الله


اجمل تحية





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ذكر
الجوزاء الديك
عدد المساهمات : 829
تاريخ الميلاد : 04/06/1993
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مُساهمةموضوع: رد: بحث حول النمل القاطع لأوراق الشجر بالانجليزية   الثلاثاء نوفمبر 23, 2010 5:44 pm

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شكـــــــــــــــــــــرا

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ذكر
الثور القرد
عدد المساهمات : 2095
تاريخ الميلاد : 17/05/1992
تاريخ التسجيل : 23/11/2010
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مُساهمةموضوع: رد: بحث حول النمل القاطع لأوراق الشجر بالانجليزية   الجمعة ديسمبر 03, 2010 12:07 pm

مشكوووووووووووووووووور
بارك الله فيك وجازاك الله خيرااا
وجعلها في ميزان حسناتك



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الدلو الخنزير
عدد المساهمات : 1712
تاريخ الميلاد : 12/02/1995
تاريخ التسجيل : 08/11/2010
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مُساهمةموضوع: رد: بحث حول النمل القاطع لأوراق الشجر بالانجليزية   السبت ديسمبر 25, 2010 7:15 pm

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