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General Ant Information
There are a vast number of ant species throughout the world, each with varying specific traits and behaviors, though they typically share some common ground. All ants are classified as the family Formicidae, in the order Hymenoptera. Ants’ bodies consist of three main segments and they have six legs. They have compound eyes and segmented antennae which they use as sensors and identifiers. Ants communicate mainly through a system of chemicals and pheromones, though at times they relay messages through ritualistic actions. Ants are fascinating in that they exhibit a social hierarchy and division of labor that is much more complex than many other species in the natural world. Workers are typically sterile females, but in some species worker ants can be fertile. Workers are, as the name suggests, the labor class and within this class there is a hierarchy of workers based on size and age. Soldiers are the fighting class, usually the largest and elder ants who defend the colony. Queens are the founders and main reproductive force and colonies. The ant life cycle begins with an egg, which is laid by a queen or fertile female ant. Fertilized eggs produce females whereas unfertilized eggs produce males. Ant eggs are approximately 1 mm long and oval shaped. However, eggs housing a queen are much larger than the others. The eggs develop into larvae, closely tended to and fed by adult workers. The larvae grow larger, molting often until they reach a certain size and pupate. Within a cocoon, they undergo metamorphosis into an adult state. The lifespan of ants varies greatly with species and queens usually live much longer than other ants. Ant colonies begin with what is called a nuptial flight. In this flight a virgin queen departs the colony, seeks a mate (in some species this is done shortly before the flight) and constructs a nest from which to begin a new colony. However, it is rare that a queen will survive long enough to achieve this due to predation and environmental hazards. Because of this, many ant species release multiple queens simultaneously. Both leafcutter and fire ants are known to release hundreds or thousands of queens at once. If successful, she will lay her first brood and tend to them. If a winged queen she will of shed her wings and now subsists off of the energy supplied by the atrophying wing muscles. The eggs will produce smaller than normal workers who begin the tasks of excavation and helping tend to larvae. When the first set of workers reaches their adult state, the queen no longer tends to the eggs but now serves in a solely reproductive capacity. Typically after the second brood has reached adulthood, the colony experiences a population boom. With colony growth energy is increasingly devoted to rearing virgin queens and males. In some species, queens of a colony will become hostile and colonies will break off into single-queen units. Gradually the fertility rate slows as colony reaches optimal size.
Leafcutter Ants
Ants of the genus Atta share the behavior of fungus culturing. Nests can exist either in trees or the ground, but all of them contain chambers of well regulated “fungus gardens”. The fungus is grown in stringy webs and well regulated by worker ants. The fungus produces small sacs called gongylidia which contain carbohydrates and nutrients. It is believed that this fungus mainly produces food for the queens and larvae, while adult ants subsist off of nutrients obtained from leaf material. The leaf cutting activity supplies the moist, organic leafy material that feeds the fungus. Workers forage for leaves and grasses and bring them to the nest to be stripped from stems and such. The ants will break off a piece of a leaf or grass, chew it until it becomes moist and pulpy, excrete a digestive enzyme onto it and carefully place it into the fungal mass. The species atta texana is a commonly referred to as the North American Leafcutter, and is prominent in North America. This is the species our group worked with. They build their nests in the ground and are capable of building massive colonies with hundreds entrance holes and thousands of chambers. Because the nature of fungus requires specific temperature and sterility requirements, leafcutters are known to close off and open holes and paths for ventilation. The labor hierarchy is very complex with leafcutters and typically workers who tend the fungal chambers never leave them and those who bring matter from the outside never enter them. Foragers will scout out, find a plant with desirable material and lay a trail for others to follow.
Harvester Ants
Harvester ants build ground nests and are typically docile in nature. They do not really attack except in defense of the colony. Harvesters, as the name implies, forage for seeds and drag them back to their nests. From these seeds they collect myrmecochores, which are nutritive caps found on seeds that help the seeds develop into plants. After the myrmecochores are extracted, the seeds are brought to the surface and discarded. Harvester ants are important in seed dispersal because at times they will accidentally abandon a seed in the foraging process. Harvesters usually do not create trails. Instead foragers work individually in finding a seed but if a seed is too large other harvesters will be recruited to help bring it home.
Fire Ants
Ants of the genus Solenopsis are commonly called fire ants. They are called fire ants not only because of their reddish coloration but their sting which can cause a burning pain. Though the sting is generally less powerful than other ants, fire ants are more aggressive and will sting much more often. The two species found in the Austin area are solenopsis invicta (imported fire ants) and solenopsis geminate (native fire ants). Solenopsis invicta are of a smaller body type are very similar to their larger cousins. They are very adaptive and are viewed as an invasive species nearly everywhere they are found. Fire ants are predacious, foraging for dead animals or outright killing them. Their food includes insects, and other ants. Also much to the chagrin of humans, they are known to enter homes in search of sugars, proteins, and fats. Fire ants are of a more internally competitive nature than most ants. Queen competition is common and at times workers will attack queens who are less productive for the colony as a whole. They are often seen as an invasive species and have ill effects on an ecosystem because they push out other ant species.
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