The leaf-cutter ant has posed serious problems for evolutionists. For what is the advantage an individual ant gains in putting all her energy into the selfless tasks of a colony, from leaf-cutting to caring for the larva to fighting as a soldier – without ever having a chance to mate and produce offspring of her own? This question has led evolutionists to one of the secrets of the superorganism. “The ants’ success lies in the evolutionary concept of kin selection” (Hoyt 1996). This concept occurs when members of a species work for the survival of relatives – genes by descent from a common ancestor rather than for one’s survival of its own offspring (which is called individual selection). This is a very complicated process in which many people have devoted their lives to its study.
The gathering of food by the leaf cutting ants is a complex series of interactions and communication which I will discuss. The foraging for food first is started from the central nest. Special ants called scouts range off of ant trails in search of food for the nest and if they find food, they start to recruit workers to collect the resource. This sounds simple but the process is actually very complicated. Using Howard, Henneman, Cronin, Fox, and Hormig’s research (1996) I will explain the process. When a scout find a food source, the decision of whether or not to recruit workers is based on the location, quantity, and quality of the source. Also the scouts examine resource consistency such as protein, lipid or simple sugar content. If a scout finds a familiar resource, it will recruit workers faster then if it found an unfamiliar resource. How much an ant is familiar with a resource was found to be in direct proportion to the number of times the ant physically touched the resource or food. The same goes with the workers. If a scout presence a worker with an unfamiliar resource, it is more likely to reject it. If the resource is accepted, the worker ant will follow the special scent trail laid down by the scout to the location of the resource. The time delay for the ants to follow a new type of food can be a negative and a positive. This can carry costs by the delay in acceptance of a new resource such as food delay, overexploitation, and starvation. This mechanism can also protect the ants in that the ants know that the food they are feeding the fungus works but a new type of food can poison the fungus.
Wirth, Beyschlag, Ryel, and Holldobler (1997) studied the cycle of foraging in the leaf-cutter ant and they found some interesting results. They found that on an average, the total yearly input of collected green leaf material corresponded to1706 to 3,855 meters square of foliage area depending on the size of the nest. The number of leaf fragments collected per day ranged from 9,770 to 374,200. During the dry season the ants harvested more leaves than the wet season due to the loss of availability of green leaves during the dry season.. Also the type of material collected during the two seasons differed. During the wet season, greater quantities of green leaves were collected while during the dry season, non green material was collected (fruit parts, stipules, and flower parts). The ants collect resources according to their availability during that time. The amount of material collected also varies with the seasons. During the wet season, more material is collected. A possible reason for this is that since during the dry season the ants collect more flowers and fruits which contain more energy then leaves, the ants don’t need as much material to feed the fungus. The rain limits the amount of foraging that can go on during the wet season by physically stopping the ants from moving on their paths due to the abundance of water on top of the soil. This may be important in regulating colony size. The average area of a leaf fragment carried by individual ants was determined to be 0.79 cm square and with an average weight of 5.51 mg. The scientists discovered that fragment area and weight was determined by the type of plant harvested. Succulent leaves (which are normally thick) were cut into small pieces (