Leaf-cutting Ants

Unknown

One of the most little known species of ants in North America is the leaf-cutter ant. This is mainly because it lives in tropical environments and it is not aggressive to animals or humans if not disturbed. The leaf cutting ant is a social insect. Alone the ant is virtually helpless but with the colony it can be a thing feared by animal and human alike. The leaf-cutting ants have a very important role in the tropical forest. They create and manipulate the environment around them. They also can do major damage.

The leaf-cutting or fungus-growing ants are distributed from northern Texas to central Argentina. These ants are injurious since they cut the green vegetation from trees, shrubs and crops, and carry it into the nest, where they cultivate fungi on it. They have been known to denude a tree or ornamental plants in one night. It has been estimated they do $1 billion damage per year in North and South America today, these ants still cause millions of dollars in crop losses in many South American countries. Although primarily an agricultural pest, this insect on occasion may invade the home 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 United States (unison services. 1998).

There are about 9,500 named species of ants. These ants are divided into 16 sub families and 300 genera, all which belong to the family called Formicidae, the family of ants (Hoyt. 1996). The leaf cutting ant belongs to the genus called Atta. There are fifteen different species of Atta and all are limited to the new world (Holldobler & Wilson, 1994).

The leaf-cutter ant looks pretty much like a regular ant in North America except that it is a little bigger than most ants. Looking at the ant in the untrained eye a person usually perceives that it is a primitive organism. Looks can be deceiving. The leaf-cutter ant is a complex superorganism unique social, environmental, and food gathering behavior.

The anatomy of the leaf-cutter ant is pretty simple.

It has a one segment "waist" (pedicel) between thorax and abdomen. Sharp spines on waist and backward from head. Antennae 11-segmented very long and elbowed without distinct club. The legs are very long. This ant can be light to dark reddish brown (Smith. 1997).

The leaf-cutter at is just like other 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 blades which they can have up to 0.5 cm space between the mandibles. The size range can be from 1/16 to 1/2 an inch depending on the type of species. The ants 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 total body length of more then 13mm) (Whitehouse & Jaffe 1996). The average worker leaf-cutter ant lives from 4-6 months (Howard, Henneman, Cronin, Fox, Hormig. 1996). The worker ants commonly perform superhuman feats.

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

The queen is the largest of the ants and can reach length larger than 1/2 an inch and her life span can be 10 years or more (Smith. 1997). The queen has wings and when she decides to leave the nest she carries a small pellet of mycelium (the fungus) in a special pocket on her head. When a new nest is found, the mycelium is used to start to grow food again. The colony growth is slow at first but soon proceeds rapidly and reaches maturity in about 5 years.

The nests of the leaf